Article in Nature Materials
Associates of the Department of Condensed Matter Physics Tina Arh, Matej Pregelj, pHD, and prof. Andrej Zorko pHD, discovered the first realization of a quantum spin liquid on a Ising triangular-lattice antiferromagnet. They performed a large scale experimental study in collaboration with the researchers from the Slovenian Institute of Mathematics, Physics and Mechanics as well as researchers from India, Great Britain, France and the USA. The results were published in Nature Materials in the article The Ising triangular-lattice antiferromagnet neodymium heptatantalate as a quantum spin liquid candidate. In addition to being a significant scientific discovery, this discovery also has an important potential for the latest quantum technologies, as spin liquids are seen as one of the most perspective platforms in quantum computing.
Article in Nature Reviews Methods Primers
Doc. dr. Matjaž Humar from the Department of Condensed Matter Physics at Jožef Stefan Institute, and researchers from UK, USA and Japan have published an article titled Whispering-gallery-mode sensors for biological and physical sensing in Nature Reviews Methods Primers. In the paper the authors introduce whispering-gallery-mode microcavities in different geometries, such as microspheres, microtoroids, microcapillaries and microrings. Whispering-gallery-mode microcavities are miniature micro-interferometers that use the multiple-cavity passes of light for very sensitive measurements at the microscale and nanoscale, including single-molecule and ion measurements. The authors describe sensing mechanisms, including mode splitting and resonance shift, and optomechanical and optoplasmonic signal transductions. Applications and experimental results cover in-vivo and single-molecule sensing, gyroscopes and microcavity quantum electrodynamics.
|Article in Physical Review X|
In an extensive study, Jeffrey C. Everts and Miha Ravnik from the Faculty of Mathematics and Physics at University of Ljubljana and the Department F5 of Jožef Stefan Institute examined the details of the coupling of ions and singular topological defects in complex nematic fluids (Phys. Rev. X 2021). The authors showed that topological defects in nematic electrolytes could perform as areas for local separation of electric charge, forming electrically charged cores of defect and in selected geometries also electrical multi-layers. These charge distribution are generalizations of electrical double layers known in isotropic electrolytes. In particular, they show that ions couple very efficiently with the defect cores through the mechanism of ionic solubility, and with the surrounding orientation field deformations through the mechanism of flexoelectricity. The work is a significant contribution towards understanding the electrostatic mechanisms in complex soft matter.
Article in Science Advances
November 11, 2021
The physical behavior of anisotropic charged colloidal particles in nematic solvents is determined by their dielectric anisotropy. Together with the experimental group of Professor Ivan Smalyukh at University of Colorado Boulder the authors Jeffrey C. Everts and Miha Ravnik from the Faculty of Mathematics and Physics at University of Ljubljana and the Department F5 of Jozef Stefan Institute demonstrated anisotropic electrostatic screening for charged colloidal particles in nematic electrolytes. The electrostatic potential and pair interactions decay with an anisotropic Debye screening length, contrasting constant screening length for isotropic electrolytes. Charged dumpling-shaped near-spherical colloidal particles in nematic media are used as model systems, demonstrating competing anisotropic elastic and electrostatic effective pair interactions for colloidal surface charges tunable from neutral to high, yielding particle-separated metastable states (Science Advances 2021, DOI: 10.1126/sciadv.abd0662). The work was published in Science Advances and contributes to the understanding of electrostatic screening in nematic media.
News & Views Article in Nature Physics
September 29, 2021
Dr. Martin Klanjšek from the Condensed Matter Physics Department published a News & Views article entitled Singlets singled out in Nature Physics upon invitation by the editor. In this article, the author presents his view of the achievements of the article Emergence of spin singlets with inhomogeneous gaps in the kagome lattice Heisenberg antiferromagnets Zn-barlowite and herbertsmithite published in the same journal by the research group of prof. Imai from the McMaster University in Canada. They report on the gradual formation of spin singlets in two quantum magnets with kagome lattice, which is an important step in the resolution of the ground state of this archetypal magnet. News & Views section contains short articles summarizing recently published high-impact research in a way accessible to the broader public. The authors of the News & Views articles are selected by the editor among those reviewers of the corresponding research articles that left the best impression during the review process.
FPPT research at JSI
March 9, 2020
Since March 2020, the researchers at "Jožef Stefan" Institute have been researching protective masks, which have turned out to be one of the key protective measures against the COVID-19 pandemic, as they reduce the aerosol viral transmissions. "Jožef Stefan" Institute researchers Anja Pogačnik Krajnc, Luka Pirker, Urška Gradišar Centa, Anton Gradišek, Igor B. Mekjavić and Maja Remškar in collaboration with other partners have recently published the article Size- and Time-Dependent Particle Removal Efficiency of Face Masks and Improvised Respiratory Protection Equipment Used during the COVID-19 Pandemic in the Sensors journal. The studied the efficiency of aerosol particle filtration for different types of masks, including masks that are categorized as PPT, as well as improvised masks, such as fabric masks, modified diving masks and modified gas masks. When it comes to different fabrics, poplin masks performed better than tetra fabrics. JSI researchers observed filtration of particles in the size order 10 to 570 nm, including the efficiency through time. These information is helps both the general public and the decision-makers in this fight against the pandemic.
Additional funding to research protective mask materials
December 17, 2020
At the 2020 ARRS call for additional funding related to COVID-19, the research program “Physics of soft matter, surfaces and nanostructures” (P1-0099, coordinator Slobodan Žumer) was successful with the proposal “Study of materials for protective respiratory face masks” prepared by Maja Remškar and Miha Ravnik. The additional 2-year funding of 2700 working hours per year will support research at IJS (two thirds) & UL FMF (one third) and collaboration with Marjan Ješelnik from the company smartMELAMINE.
Prof. dr. Samo Kralj received Zois Certificate
December 4, 2020
This year's winners of the Slovenian highest awards for science were presented on December 1, 2020, in a documentary Highlights of Slovenian Science through the eyes of award winners for outstanding achievements 2020. One of the award winners is prof. dr. Samo Kralj from the Condensed Matter Physics Department who received the Zois Certificate of Recognition for important research achievements in the field of soft matter physics. Congratulations!
Article in Advanced Materials
November 27, 2020
Dr. Simon Čopar form the Faculty of Mathematics and Physics, University of Ljubljana, and dr. Uroš Tkalec from the Condensed Matter Physics Department at the »Jožef Stefan« Institute in collaboration with Korean researchers led by Dong Ki Yoon have published article Periodic Arrays of Chiral Domains Generated from the Self-Assembly of Micropatterned Achiral Lyotropic Chromonic Liquid Crystal in the ACS Central Science. The article includes both the experimental demonstration and theoretical explanation of the phenomena and is an important contribution towards practical use of chiral structure made from water-based non-chiral LC-molecules. It was highlighted on the front page of the November issue of the journal, which also included a commentary by Oleg Lavrentovich from Kent State University.
Article in Advanced Materials
October 27, 2020
Led by dr. Janez Štrancar, PhD, the researchers of the Biophysics Laboratory of the Condensed Matter Physics Department at the “Jožef Stefan” Institute have made crucial contributions to a large study of the mechanisms for nanomaterial toxicity and inflammation predictions without the use of test animals, published in the Advanced Materials under the title Prediction of Chronic Inflammation for Inhaled Particles: the Impact of Material Cycling and Quarantining in the Lung Epithelium. As part of the SmartNanoTox Horizon 2020 Projects, the Biophysics Laboratory coordinated the work of 34 authors from 9 countries. The authors of the article are the first to identify the key molecular events involved and connect them into a complicated cyclic mechanism that triggers different inflammatory responses. This knowledge allowed them to develop a model for predicting chronic inflammations using only selected cell tests. These findings are already being used to develop autonomous detection systems to predict the safety of materials, chemicals, medications or vaccines.
Article in Journal of Membrane Science
October 14, 2020
As the beginning of the COVID-19 pandemic caused a general lack of medical protective equipment, the researchers from “Jožef Stefan” Institute, including associates of our department, decided to look into the option of using ionizing radiation to sterilize used masks and allow their reuse. The results showed that facepiece respirators type FFP2 and FFP3 can be sterilized by Gamma irradiation and electron beam irradiation. This method of sterilization preserves the mechanical and chemical characteristics of masks and does not harm the efficiency of aerosol particle filtration. While 20 kGy radiation does cause the loss of the polypropylene membrane filters static charge, re-application of the charge brings the filtration efficiency back to the previous level. Masks can be sterilized up to two times using this method. The research was carried out by Luka Pirker, Anja Pogačnik Krajnc, Anton Gradišek, Andreja Jelen, Maja Remškar, Igor B. Mekjavić, Janez Kovač, Miran Mozetič, Luka Snoj, Jan Malec and Vladimir Radulović, and the results were published in the Journal of Membrane Science in the article entitled Sterilization of polypropylene membranes of facepiece respirators by ionizing radiation.
Article in Journal of Advanced Electronic Materials
October 6, 2020
Abdou Hassanien from the F5 Department of Jozef Stefan Institute has published, in collaboration with Biao Zhou and Akiko Kobayashi from Nihon University, Tokyo, Japan, an article in the Journal of Advanced Electronic Materials titled Spontaneous Antiferromagnetic Ordering in a Single Layer of (BETS)2GaCl4 Organic Superconductor. The fabrication of such well-defined and atomically clean interfaces between materials of different orders are of fundamental interest to engineer novel functionalities and to study emergent phenomena in condensed matter physics. The paper illustrates the interplay between electronic orders of hybrid mix of nested antiferromagnetic molecular chains and superconducting molecular stripes at the single layer limit. Results of low temperature scanning tunneling microscopy and spectroscopy have shown that low level vibronic and magnetic excitations that dominate the higher temperature phase are absent below Tc which point to their cooperative existence and possible renormalization to mediate superconductivity in such d-wave superconductors.
Article in Physical Review X
September 25, 2020
Guilhem Poy from Faculty of Mathematics and Physics at University of Ljubljana and Slobodan Žumer from Jozef Stefan Institute in collaboration with the group of Ivan Smalyukh from University of Colorado in Boulder in Physical Review X published the paper that Control of Light by Topological Solitons in Soft Chiral Birefringent Media, was highlighted in APS Physics Focus by the editorial article “Liquid-Crystal Vortices Focus Light”. Topological solitons appearing in different areas of physics are fascinating localized perturbations of ordering fields enjoying topological protection. The authors demonstrate refraction, reflection, and lensing of weak laser beams by various topological solitons in frustrated chiral nematics and show how interactions of light with such topological solitons are well described using a generalized Snell’s law and ray-tracing models. These may lead to new means for controlling flow of light for use in optics and photonics.
Article in Physical Review Letters
September 1st, 2020
Slobodan Žumer from Jozef Stefan Institute and Guilhem Poy from Faculty of mathematics and Physics at University of Ljubljana in collaboration with Andrew Hess and Ivan Smalyukh from University of Colorado in Boulder published the paper Chirality-enhanced periodic self-focusing of light in birefringent soft media in Physical Review Letters. It presents numerical, experimental and theoretical evidence of chirality enhanced nonlinear optical response of frustrated chiral nematics. In achiral nematics, the reorientation of molecules around laser beams with appropriate power is responsible for the generation of spatial optical solitons called "nematicons". In unwounded chiral nematics, the frustration caused by a confinement incompatible with their lowest-energy states allows a relatively weak light to locally destabilize the initially uniform orientational fields and thus boost their nonlinear optical responses. Our research findings are expected to allow new self-focusing based applications.
Athena gender equality project
August 13, 2020
As a member of an international consortium, “Jožef Stefan” Institute received the European Athena project, whose aim is the implementation of gender equality plans to release the potential of research institutions in Europe. The F5 department will have an active role in this project, joined by 9 other “Jožef Stefan” Institute departments (U1, F4, K1, K3, K5, K7, E3, E5 and E7). Despite the large number of highly qualified women with degrees, women make up only a third of research workforce in the EU. The aims of this project are to remove the barriers that make it difficult for women to become employed in a research facility and to be promoted to researchers, to strengthen the presence of the gender dimension within research programs and to address the gender inequality in decision making. The two main project goals are development and implementation of a plan for gender equality on a systemic, institutional level. The members of the international consortium are research institutions from Central and Eastern Europe and from remote regions with a low gender equality index, as the project aims to reduce the gap between research organizations across Europe.
Article in Physical Review Letters
July 13, 2020
Tina Arh, Matjaž Gomilšek, Matej Pregelj, Martin Klanjšek and Andrej Zorko from the Solid State Physics Department and Peter Prelovšek from the Department of Theoretical Physics at the “Jožef Stefan” Institute, in collaboration with researchers from United Kingdom, USA and China, have published a paper “Origin of Magnetic Ordering in a Structurally Perfect Quantum Kagome Antiferromagnet” in Physical Review Letters. They confirmed more than a decade old theoretical prediction of a quantum critical point of a kagome antiferromagnet between a quantum spin liquid and a magnetically ordered state, induced by the Dzyaloshinskii-Moriya magnetic anisotropy. YCu3(OH)6Cl3 is the first known material with a perfect kagome lattice without any impurities, in which the magnetic anisotropy can be studied in isolation from other perturbations. Understanding the mechanism of magnetic ordering in this material is crucial for understanding the stability of enigmatic quantum spin liquids.
Increased nanoparticle exposure due to pyrotechnics during a football match
June 15, 2020
During a football match at the Stožice Stadium in Ljubljana in 2019, the F5 department researchers measured nanoparticle air pollution. During the match, the fans of both teams used pyrotechnic devices to support their teams despite the prohibition. Researchers of the Department of Condensed Matter Physics, Luka Pirker, Anton Gradišek, Bojana Višić and Maja Remškar discovered the number of nanoparticles in the range between 30 nm to 300 nm increased by 1200 percent when flares were light and the players inhaled 300 % more particles than usual. In addition to carbon, the chemical analysis also showed the presence of potentially poisonous elements which are used for colouring and as fuel such as strontium (red colour), barium (green colour), potassium, magnesium and chloride. The findings were published in the Atmospheric Environment journal.
Article in Nature Physics
February 19, 2020
Andrej Zorko from the Department of Condensed Matter Physics at Jožef Stefan Institute and the Physics department at the Faculty of Mathematics and Physics, University of Ljubljana, was part of the international research team that confirmed the gapless ground state in the archetypal quantum kagome antiferromagnet ZnCu3(OH)6Cl2. Their research, which was published in the Nature Physics journal, disproved the decades old conviction that a spin-gap must exist in this material and shone new light on the enigmatic state of this spin liquid. This experimental conclusion aligns with the most recent theories which propose a gapless Dirac spin liquid as the ground state of the Heisenberg kagome antiferromagnet.
Article in Nature Communications
January 16, 2020
A team of researchers from the Faculty of Mathematics and Physics and Faculty of Medicine, University of Ljubljana, and »Jožef Stefan« Institute, including Uroš Tkalec from our department, have studied previously unresearched dynamic chiral states which arise before the homeotropic to flow-aligned transition. In the article published in the Nature Communications journal, they explain the mechanism of phase transitions between topologically different states of pressure driven liquid crytal with a phenomenological model based on the anisotropy of elastic constants and completed the phase diagram of all observed hydrodynamic states. These concepts could also be used in lyotropic and active nematic liquids with nematic order.
Article in Physical Review XDecember 23, 2019
Simon Čopar, Jure Aplinc, Žiga Kos, Slobodan Žumer and Miha Ravnik, researchers from the Department of Condensed Matter Physics and the Physics Department of the Faculty of Mathematics and Physics, University of Ljubljana, were the first team who managed to research the topology of three-dimensional active nematic turbulence under the spherical confinement. Based on mesoscopic imaging, they used numerical modeling to show the dynamics in active nematics – usually complex biological liquids, in which the particles propel themselves using energy they receive from the environment. The team described the complex chaotic dynamic of active turbulence using topological events that govern the defects appearing in such matter. They also demonstrated coupling of surface and bulk topological defect dynamics by changing from strong perpendicular to in-plane surface alignment. This article, published in Physical Review X, importantly contributes to our understanding of the quickly evolving field of active soft matter.
Best Oral Presentation AwardDecember 12, 2019
At the international conference European C-MetAC Days 2019, held in December 2019 at the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany, Darja Gačnik received the award for the best oral presentation in the young scientists’ category. In her presentation Superconductivity in Ti–Zr–Hf–(Sn,Ni,Nb) high-entropy alloys she presented her research of superconductivity in a new type of metal alloys, called high-entropy alloys. The research results she presented were uncovered in collaboration with her co-workers at the Department of Condensed Matter Physics (S. Vrtnik, A. Jelen, M. Krnel, P. Koželj, J. Dolinšek) and dr. Qiangom Hujem from the Institute of Applied Physics at the Jiangxi Academy of Sciences, Nanchang, China.
Article in Scientific ReportsDecember 12, 2019
An article conceptualised by Abdou Hassanien, associate Department of Condensed Matter Physics at the “Jožef Stefan” Institute, and co-written by Alexander Vahl, Niko Carstens, Thomas Strunskus in Franz Faupel from the Christian-Albrechts-University of Kiel, Germany, was published by Scientific Reports. The article describes behaviour of memristors (memory resistors) at the level of individual nanoparticles to find the best conditions for robust operation of devices. Their discoveries also help understand the underlying physical mechanisms. Furthermore, they discovered that application of alloy nanoparticles effectively limits the formation of stable metallic filaments and results in reproducible diffusive switching characteristics.
Jean-Pierre Bourguignon visits the F5 DepartmentDecember 4, 2019
Jean-Pierre Bourguignon, president of the European Research Council, visited Slovenian for the third time on November 28, 2019. In the morning he visited the Faculty of Mechanical Engineering at the University of Ljubljana. In the afternoon he met with representatives of the “Jožef Stefan” Institute, primarily with the ERC grant winners, dr. Dragan Mihailovič and our own dr. Matjaž Humar. He also visited the laboratories of the Department for Condensed Matter Physics where dr. Humar’s Cell Lasers Project is being undertaken. In addition to boosting the international visibility of the researchers, the ERC grants also allow them to implement several years of independent research at the highest level, including the acquisition of the necessary research equipment.
Žiga Zois Prizes and AwardsNovember 22, 2019
On November 20, 2019, the Republic of Slovenia awarded the highest prizes and awards for outstanding achievements in science, research and development to 18 top scientists. Among them were two associates of the Department of Condensed Matter Physics. Professor dr. Desnis Arčon received the Žiga Zois prize for outstanding achievements in the fields of quantum magnetism and unusual superconductivity and assistant professor dr. Miha Ravnik received the Žiga Zois Award for outstanding achievements in the field of soft matter physics.
Professor dr. Nives Ogrinc from the Department of Environmental sciences and professor dr. Boris Rogelj, head of the Department of Biotechnology were also among the 18 awarded scientists.
Dr. Brigita Rožič – winner of the Fulbright grantNovember 13, 2019
Brigita Rožič, researcher of the Department of Condensed Matter Physics at the “Jožef Štefan” Institute, has received the Fulbright grant for her excellent scientific and research work. The Fulbright grant is awarded every year to successful scientists from all over the world. In Slovenia this grant is awarded by the US Embassy in Ljubljana as part of the Fulbright programme financed by the US government. The grant further inspired dr. Rožič for her future research and increased her visibility as well as the visibility of the “Jožef Štefan” Institute. The grant allowed her to do research at the Case Western Reserve University with prof. Charles Rosenblatt’s team, working in an area that was entirely new to her. Furthermore, she loved living in Cleveland, whose many lakes and wonderful environment reminded her of home. Dr. Rožič also received congratulations for the award from the president of the United States.
October 28, 2019
Dr. Martin Klanjšek, associate of the F5 Department, was awarded the Blinc Award for Extraordinary One-time Achievements for proving the existence of unusual quasiparticles called anyons.
On October 24, 2019, the Faculty of Mathematics and Physics of the University of Ljubljana and the “Jožef Stefan” Institute awarded the first Blinc awards for research and theoretical work in physics. The awards were founded to celebrate the best physicists and to commemorate Robert Blinc, one of the sharpest Slovenian researchers and a member of the Slovenian Academy of Science and Arts.
Two other awards were bestowed in addition to the Blinc Award for Extraordinary One-time Achievements: prof. dr. Matjaž Perc from the Faculty of Natural sciences and Mathematics was awarded the Blinc Award for Physicist at the Beginning of their Career and prof. dr. Peter Prelovšek, the most visible Slovenian researcher in the field of theoretical physics of condensed matter in Slovenian and abroad, received the Blinc Award for Lifetime Achievement.
|ERC Starting Grant|
September 4, 2019
Dr. Matjaž Humar, head of the Bio-integrated photonics lab and associate of the Condensed Matter Physics Department at the Jožef Stefan Institute was awarded the prestigious ERC Starting Grant by the European Research Council in the amount of 1.5 million Euro. The aim of the Cell Lasers Project is to study the interactions between lasers inserted into individual cells and the biological processes within those cells. Dr. Humar recently presented the first example of a laser within a living cell. Previous research has shown that lasers can operate within cells, but it has not yet been researched how the operation of lasers interacts with biophysical and biochemical processes of the cell. In the long term, the Cell Lasers Project aims to transform lasers within cells from a scientific curiosity into a robust method that can be used in the fields of research and medicine.
|Best poster at the ICQ14|
May 31, 2019
The International Conference on Quasicrystals – ICQ14 took place in Kranjska Gora from May 26 to May 31, 2019. It was attended by 120 scientists from 18 countries and three continents (Europe, Asia and America). Dr. Andreja Jelen of the F5 Department also attended the conference, where she presented the poster “Microstructure and magnetic properties of a single-crystalline FeCoCrMnAl high-entropy alloy”. The committee of three scientists from France, Japan and Poland selected her poster as the best poster contribution at the ICQ14 conference. The Best Poster Prize was sponsored by the Crystals journal. The photo shows dr. Andrej Jelen and the president of the committee, prof. Hiroyuki Takakura from the University of Hokkaido, Japan.
|Article in Nature Physics|
May 27, 2019
Matjaž Gomilšek, Martin Klanjšek, Matej Pregelj and Andrej Zorko from the Condensed Matter Physics Department and Rok Žitko from the Department of Theoretical Physics at the “Jožef Stefan” Institute, in collaboration with researchers from Switzerland and China, have published the paper Kondo screening in a charge-insulating spinon metal in Nature Physics. The Kondo effect where conduction electrons screen the local moments of magnetic impurities is well known to occur in ordinary metals. Here, the researchers have shown that an analogous phenomenon is possible also in electric insulators, in particular, in a quantum spin liquid with magnetic spinon excitations forming a Fermi surface. This discovery could be important for manipulating topologically protected spin-liquid states in quantum computing.
|Article in npj Quantum Materials|
May 3, 2019
Researchers from the Condensed Matter Physics Department (F5), Matej Pregelj, Andrej Zorko, Matjaž Gomilšek, Martin Klanjšek and Denis Arčon, in collaboration with colleagues from Switzerland, UK and Croatia, published an article in npj Quantum materials entitled Elementary excitation in the spin-stripe phase in quantum chains. To describe the dynamics of a large number of interacting particles, we often use a decomposition into elementary excitation modes, such as phonons in case of lattice vibrations. In the published article, the researchers discovered a new excitation mode in the spin chains, a collective wiggling of spins occurring in a spin-stripe state. The work provides a new insight into the physics of stripe states, which are also found in high-temperature superconductors.
|Dr. Koželj awarded the JSI Golden Emblem Prize|
March 27, 2019
For the 27th time, the Jožef Stefan Institute awarded the Golden Emblem Prize to authors of doctoral theses with the highest impact in Slovenia and abroad, which were defended in the Republic of Slovenia in the past three years. This year, the Golden Emblem was awarded to dr. Primož Koželj and dr. Victor Vega Mayoral. Dr. Koželj received the Golden Emblem for the high impact of his dissertation “Physical Properties of High-Entropy Alloys and their Comparison to Complex Intermetallics” and dr. Mayoral for his dissertation “Photophysics of transition metal dichalcogenides obtained from liquid phase exfoliation”. The Golden Emblems were awarded on March 27, 2019, in the Cankarjev dom conference centre as part of the celebration in honour of 70 years of the Jožef Stefan Institute. Keynote speakers were the director of JSI, prof. dr. Jadran Lenarčič, and president of the Republic of Slovenia, Mr. Marjan Šarec.
|Article in Science Advances|
February 15, 2019
The article Sculpting stable structures in pure liquids prepared by Tadej Emeršič, Žiga Kos, Simon Čopar and Natan Osterman from the University of Ljubljana and Rui Zhang and Juan J. de Pablo from the University of Chicago under the guidance of Uroš Tklalec from the Department of condensed matter physics at the Jožef Stefan Institute was published in the journal Science Advances. The authors reported on controlled creation of microdomains with polar order in nonequilibrium nematic liquid crystal using flow and light pulses. This is an important step in the process of sculpting of complex liquids with external fields, as it represents the first example of stabilisation of dynamic segments in a single-component anisotropic liquid. The method enables manipulation of the boundary between orientational phases and encapsulation of other molecules and can be used in active biological systems.
|Condensed Matter Physics at TEDxLjubljana 2018|
December 13, 2018
TEDxLjubljana2018 was held on December 9, 2018, at the Cankarjev dom conference centre. One of the speakers was Griša Močnik, associate of the Condensed Matter Physics Department. He used the closure of the Slovenska Road in Ljubljana to showcase black carbon as a useful “tool” for measuring the effectiveness of measures taken to improve air quality. He also invited the audience to adopt simple behavioural changes which can help improve the quality of life for everyone.
|Article in Science Advances|
November 27, 2018
The article Mosaics of topological defects in micropatterned liquid crystal textures written by Dae Seok Kim and Dong Ki Yoon from the KAIST Institute in South Korea, Simon Čopar from the Faculty of Mathematics and Physics, University of Ljubljana, and Uroš Tkalec, associate of the Condensed Matter Physics Department at the Jožef Stefan Institute, was published in the Science Advances journal. The article presents an experimental method of controlled creation of micropatterned topological defects in thin layers of nematic and smectic phases in liquid crystals using micropatterned surfaces. The created patterns are very robust, colourful and responsive to the changes in the thickness of the layer and the temperature. The patterns can cover several square centimetres of the surface, follow the symmetrical rules on topological charge conservation and look like ceramic or glass mosaics or stained glass patterns.
|Dr. Posnjak's doctoral thesis published by Springer|
September 21, 2018
Monograph Topological formations in chiral nematic droplets written by Gregor Posnjak from the F5 Department has been published by Springer. The book was published in the Springer Theses series, which focuses on dissemination of outstanding and relevant doctoral theses. Dr. Posnjak’s theses, which he defended in 2017 at the Faculty of Mathematics and Physics of the Univeristy of Ljubljana under the mentorship of prof. dr. Igor Muševič, discusses complex structures of chiral nematic liquid crystals. In his theses, Dr. Posnjak reported the first observation of topological point defects with higher topological charges q = −2 and q = −3 and developed a new augmented fluorescent confocal polarising microscopy method for reconstruction of director fields in experimental conditions.
|Article in Nano Letters |
July 24, 2018
Researchers from Jožef Stefan Institute (IJS) I.Urbančič, M.Garvas, H.Majaron, B.Kokot, P.Umek, Z.Arsov, T.Koklič, M.Škarabot, I.Muševič in J.Štrancar (F5) and M.Čeh (CEMM in K7) as well as from University of Oxford (UO) F.Schneider, S.Galiani in C.Eggeling and from from University College Dublin (UCD) have identified the causal connection between inhalation of nanoparticles, lipid wrapping and triggerring of the coagulation signal cascade in lung epithelium. Recently installed super-resolution STED microscope significantly contributed to this findings together with expertise transfer from UO and new proteomics techniques at UCD. The work entitled Nanoparticles Can Wrap Epithelial Cell Membranes and Relocate Them Across the Epithelial Cell Layer was published in Nano Letters.
|Cover and article in Small|
June 27, 2018
Collaboration between Tilen Koklič from the F5 Department and N. Aničić, M. Vukomanović and D. Suvorov from the K9 Department resulted in discovery of basic principles of contact-based mechanism of MgO antibacterial activity. Their research confirmed the key role of MgO surface defects in hydrolysis, antibacterial activity and ROS generation, setting guidelines for further development of MgO-based medical devices. The findings were published in the Small journal and the research illustration was chosen as the cover of the June issue.
|Article in Nature Physics |
8 May, 2018
Nature Physics published an article entitled Observation of two types of fractional excitation in the Kitaev honeycomb magnet by members of the Condensed Matter Physics Department at Jožef Stefan Institute, Nejc Janša, Andrej Zorko, Matjaž Gomilšek, Matej Pregelj and Martin Klanjšek, and colleagues from Switzerland. The article describes the first clear confirmation of the existence of two types of anyonic quasiparticle in a layered crystal α-RuCl3, which is known as the best realization of the Kitaev honeycomb lattice. A decade old famous Kitaev prediction spurred numerous experimental efforts to confirm the existence of anyons. The discovery is important also as the braiding operations with anyons offer one of the most promising platforms for topological quantum computing.
|Image captured by F5 associates on the cover of Liquid Crystals |
January 15, 2018
An image captured by the Calorimetry and dielectric spectroscopy group of the F5 Department was published on the cover of the August issue of the Liquid Crystals Journal. An article of frustrated liquid-crystalline TGB phase stabilisation in the presence of nanoparticles was published in the same issue, based on the study by Maja Trček, George Cordoyiannis, Brigita Rožič, Vassilios Tzitzios, George Nounesis, Samo Kralj, Ioannis Lelidis, Emmanuelle Lacaze, Heinz Amenitsch and Zdravko Kutnjak. The background of the image shows the texture of the TGB order as captured with a camera under a polarised optical microscope. The foreground of the image shows a schematic rendering of the TGB phase structure. The TGB phase is stabilised in a mixture of chiral liquid crystal and nanoparticles. The nanoparticles populated the topological defects of the screw dislocations which are located between the blocks in smectic order.
|Dr. Koželj receives Best Oral Presentation Award at C-MAC Dasy 2017|
5 December 2017
At the international C-MAC Days 2017 conference held at the end of November in Athens, Primož Koželj, PhD, was awarded the Best Oral Presentation Award in the Young Scientists category. In his invited lecture, Dr. Koželj spoke about the magnetism of eutectic high-entropy alloys CoCrFeNiZrx and proved the existence of multi-component magnetic structure inside them, which is the consequence of a complicated microstructure consisting of the eutectic matrix made from two phases and dendrites. The presented research was based on a collaboration between the associates of the Department of Condensed Matter Physics at the JSI (P. Koželj, S. Vrtnik, A. Jelen, J. Luzar, A. Kocjan, J. Dolinšek) and their Slovene colleagues at the Faculty of Chemistry and Chemical Technology of the University of Ljubljana and the Institute of Mathematics, Physics and Mechanics, as well as international collaboration with Swedish (Chalmers University of Technology) and South Korean (Korea Basic Science Institute) scientists.
17-21 July 2017
The Liquids 2017 conference, organised by the »Jožef Stefan« Institute and the Faculty of Mathematics and Physics of the University of Ljubljana, was held form 17 to 21 July in Ljubljana. The largest liquid matter science event of this year brought together more than 600 experts on liquids, foams, polymers, colloids, glasses, active systems and biomaterials from the greatest institutions in the world. Two prestigious awards were also awarded at the comference to two leading global scientists: »Liquid Matter Prize« to prof. Jacobu Kleinu (Weizmann Institute of Science, Izrael) and the »Pierre-Gilles de Gennes lecutre« to prof. Raminu Golestanianu (University of Oxford, VB).
|Third Conference of young researchers and students|
4 July 2017
On 4 July 2017, the third Conference of young researchers and students was held at the "Jožef Stefan Institute", under the honorary patronage of academician Tadej Bajd, president of the Slovenian Academy of Sciences and Arts. In the morning, the present ministers and the hosts stressed the importance of circulation of knowledge, ideas and practices among the young in Slovenia, across the borders and abroad. Then Matjaž Humer from the Deparment of Condensed Matter Physics and Igor D. Gregorič, cardiovascular surgeon who has been operating in the USA for the last 30 years, presented their career paths as an inspiration for future generations. In the afternoon, numerous participants talked about topics such as a successful career path as a challenge for the next generation, the opportunity presented by exchanges, the challenge of finding employment for young Slovenes abroad and networking of young Slovene researchers.
|Paper in ACS Nano|
22 June 2017
Brigite Rožič, associate of the Department of Condensed Matter Physics, published a paper titled Oriented Gold Nanorods and Gold Nanorod Chains within Smectic Liquid Crystal Topological Defects in the renown scientific journal ACS Nano. Gold nanorods attracted a lot of interest thanks to their unique optical characteristics based on the localised surface plasmonic resonance and to the many options for their application. However, for maximum efficiency, gold nanorods must be well ordered. B. Rožič, in collaboration with scientists form France, Germany and the USA, was among the first to prove that smectic liquid-crystal defects can be used to organise gold nanorods of different sizes into ordered superstructures and create a new efficient plasmonic system. This even more options for application of gold nanorods for example in optics and photonics.
Bose-Einstein Condensation of Cesium atoms
31 March 2017
Researchers of the Laboratory for Cold Atoms at the Condensed Matter Physics Department F5 have confirmed Bose-Einstein Condensation (BEC) of Cesium atoms on March 31, 2017. They used the laser light to cool Cesium atoms to temperatures near absolute zero (below 20 nK) and compressed them into BEC using light and magnetic fields. The picture shows cooling and compression of cold atoms into BEC, forming a coherent cloud of 50 microns diameter containing 15.000 atoms. In this fascinating quantum matter, quantum physics is observable at the macroscopic level, making it an ideal system to simulate quantum phenomena, study quantum computing, or using quantum physics for metrology. With this achievement the Department joined a prominent laboratories performing experiments in quantum technologies.
|Hidden topological constellations and polyvalent charges in chiral nematic droplets|
21 February 2017
The Nature Communication journal published the article Hidden topological constellations and polyvalent charges in chiral nematic droplets by Gregor Posnjak, Simon Čopar and Igor Muševič, associates of the F5 Department for Condensed Matter Physics at the J. Stefan Institute and the Faculty for Mathematics and Physics at the University of Ljubljana. The authors were the first in the world to reconstruct the order of molecules in micrometer-sized droplets of chiral nematic liquid crystal, for which they used a state-of-the-art method of 3D fluorescent confocal microscopy, and discovered divers topological states, including chins of topological defects and point defects with a multiple of the basic topological charge. The ordering of the molecules around these topological defects is similar to the atoms with high valence and enables the construction of complex topological molecule-like structures.
|First successful catalysis of aldol condensation with protonated titanate nanotubes|
February 5, 2017
The associates of the »Jožef Stefan« Institute, Melita Sluban (F5), Polona Umek (F5) and Jernej Iskra (K3), in collaboration with the researchers from the University of Ljubljana (Faculty of chemistry and chemical technology) and the University of Bucharest, for the first time successfully catalysed the aldol condensation, which is the most common reaction for creation of new carbon-carbon bonds, using protonated titanate nanotubes. Such a reaction is a 'green' alternative to the current industry practice of using stoichiometric amounts of homogeneous catalyst, which cannot be recycled after the reaction ends. In contrast, when using protonated titanate nanotubes, a mere catalytic amount of material ensures a successful reaction, the catalyst can be used several times and it was even successful in a large-scale experiment. The work was published in the article Protonated titanate nanotubes as solid acid catalyst for aldol condensation in the Journal of Catalysis, one of the lead journals in the field of catalysis.
|Paper in Nature Communications|
January 24, 2017
On January 24, 2017, Nature Communications published a paper called Fractal Nematic Colloids written by Uroš Jagodič, Igor Muševič and Miha Ravnik, associates of the Department for Condensed Matter Physics (F5) at the "Jožef Stefan" Institute and of the Faculty of Mathematics and Physics at the University of Ljubljana in collaboration with the associates of the Sharif University of Technology in Iran. They used two-photon laser lithography to create colloidal particles in the shape of fractal Koch stars, which they studied in liquid crystal. The fractal particles influence the ordering of the liquid crystal and create topological defects, whose number increases exponentially in accordance with the fractal order of particles. This is the first time that fractal states were created in soft matter.
|Paper in the Physical Review Letters|
January 5, 2017
The Physical Review Letters published a paper called Low-Temperature Global Symmetry Reduction in the Kagome Antiferromagnet Herbertsmithite by Andrej Zorko and Matjaž Gomilšek, associates of the Department for condensed matter physics at the "Jožef Stefan" Institute. In collaboration with groups from Croatia, USA and France, they were the first to observe symmetry brake in a Herbertsmithite crystal, which is known as the paradigm of a quantum antriferromagnet on a Kagome spin lattice, where the theory predicts a magnetic disordered ground state of spin liquid. Such break could hold the key information on the essential nature of the magnetic ground state of this crystal. After more than a decade of intensive research, this discovery offers a completely new insight into the enigmatic ground state of a spin liquid on a Kagome spin lattice.
Paper in the Proceedings of the National Academy of Sciences of the United States of America
November 21, 2016
The journal Proceedings of the National Academy of Sciences of the United States of America published a paper entitled Working stroke of the kinesin-14, ncd, comprises two substeps of different direction, written by Andrej Vilfan, associate of the F5 Department, in collaboration with two groups from Dresden and Warsaw. Molecular motors such as myosin, kinesin and dynein transform chemical energy into mechanical work performed through longitudinal movement along the citosceletal fillaments. In many cases, the torque also causes the fillaments to swivel. The article talks about the measurments performed on the kinesin-14, a motor involved in the cell division. By observing the translation and rotation in different chemical circumstances, we can use theoretical modeling to reconstruct the work cycle of the motor. The results show how measurements on a larger ensemble allow us to determine the characteristics of an individual molecules.
Dr. Janez Pirš awarded the Hononrary distinction of 'Jožef Stefan' Institute
October 20, 2016
On October 20, 2016, the Scientific Counsil of the J. Stefan Institue warded the Honorary distinction of the 'Jožef Stefan' Intitute to dr. Janez Pirš. Dr. Janez Pirš was awarded the Honorary distinction for his contribution to development of new high-tech products based on scientific and technological achievements of the 'Jožef stefan' Institute. Dr. Janez Pirš worked for a long time at the F5 department and was the instigator of the first real collaboration with Slovene industry in 1980. His most important achievement was the collaboration between the Institute and the Balder d.o.o. company, which was in 1997 created as a sipin-off company od the Institute for development, production and selling of protictive weldinf filters. Thanks to dr. Janez Pirš, the 'Jožef Stefan' Insitute and Balder d.o.o. have been successfully collaborating from the very begining, and this collaboration continued also after 2012, when Balder d.o.o. became part of the international company Kimberly Clark Proffesional.
|Article in Nature Communications|
October 7, 2016
Liquid crystal elastomers are promising for building actuators due to their excellent thermomechanical response, but it is challenging to manufacture them additively. Members of the Solid State Department (F5) of Jožef Stefan Institute, A. Rešetič, J. Milavec, B. Zupančič, B. Zalar and V. Domenici from Italy have shown that limitations imposed by the synthesis of liquid crystal elastomers can be overcome by doping microparticles to the polymer matrix and curing the composite resin in external magnetic field. The new composite material provides for conventional moulding of elastic objects of general shapes and thermomechanical deformation modes. This work has been published in an article Polymer-dispersed liquid crystal elastomersin Nature Communications.
September 14-16, 2016
From September 14 to Septemebr 16, 2016, the 'Jožef Stefan' Institute hosted the 6th Workshop on Liquid Crystals for Photonics, which brought together world first class scientists, in particular physicists, chemists and engineers, involved in photonic applications of liquid crystals. The workshop was co-organised by the 'Jožef Stefan' Institute and by the Group for Physics of Soft and Partially Ordered Matter from the Faculty of Mathematics and Physics of the University of Ljubljana.
|1st Place Poster Prize at the Lindau Nobel Laureate Meetings|
July 2, 2016
Matjaž Humar from Condensed Matter Physics department at Jožef Stefan Institute won 1st Place Poster Prize at prestigious Nobel Laureate Meeting 2016. The meeting has taken place in Lindau, Germany from 26. June to 1. July. There were 400 invited young scientists from 80 countries and 29 Nobel laureates attending the 66. Lindau Nobel Laureate Meeting. The attendees of the meeting are carefully selected by a committee giving priority to young scientists who are strongly committed to science and research. This year meeting was focused on physics. Matjaž presented a poster about lasers embedded into single live cells. His poster got the most votes given by the young scientists and Nobel laureates.
|Dr. Matjaž Humar receives funding for Live and Edible Photonics Project|
June 24, 2016
Director's Council reached an unanimous decision to finance the Live and Edible Photonics Project, proposed by dr. Matjaž Humar form the Departement for condensed matter physics. The goal of the project is to build a leading bio-integrated photonics laboratory in the 'Jožef stefan' Institue. The laboratory will be located in the former library rooms, which will be renovated and adapted to form the perfect environment for the proposed studies. The laboratory will develop photonic components, such as laser, made entirely of biocompatible and living materials, which will be suitable for consumption or for insertion into a human body. Biodegradable photon sensors will also be used in combination with optically coherent tomography (OCT) and will enable the use of sensors deeper inside the body than before and with greater resolution. OCT will be used to study live active self-organising systems and their interaction with light. The methods developed as part of the Project will allow a new level of manipulation of biological systems, biosensing and new human-machine interfaces.
|Article in Scientific Reports|
20 May, 2016
The journal Scientific Reports published on May 20, 2016 the article entitled "Points, skyrmions and torons in chiral nematic droplets", by Gregor Posnjak, Simon Čopar and Igor Muševič, members of the Solid State Department (F5) of JSI and Faculty of Mathematics and Physics, University of Ljubljana. They discovered a new method of reconstructing 3D orientational field of a liquid crystal, labelled with fluorescent molecules and imaged with a confocal optical microscope. Using this method they were able for the first time to determine unambigously the topological properties of a chiral liquid crystal, captured in a micro-droplet, as tiny as a hair. They could see singular point-like topological defects, separated by 3D topological objects, which are known in physics as skyrmions and torons.