1990–1994

Year 1990

In 1990, the following laboratories operated within the Department for Condensed Matter Physics:

• Nuclear Magnetic Resonance Laboratory,
• Biophysics Laboratory,
• Quantum Optics Laboratory,
• Dielectric Spectroscopy Laboratory,
• NMR Tomography Laboratory.

Three applied research groups still operated within the Department:

• research group for application of ferroelectrics,
• research group for application of liquid crystals,
• research group for utilisation of NMR.

The work of the independent electron microphysics and surface physics laboratory also deserves a mention.

The main fields of study in 1990 were:

• research of disordered ferroelectrics, proton and deuteron glasses,
• research of incommensurate systems,
• research of polymer-dispersed liquid crystals and ferroelectric liquid crystals,
• research of new methods of double nuclear resonance and two-dimensional NMR spectroscopy,
• research of quantum optics,
• research of high-temperature superconductors,
• research of microstructure of thin layers and defects in crystals,
• research of membrane biophysics, especially of transport processes and reactions coupled with transport.

In 1990, the studies resulted in many important findings, such as:

• It was determined that the static dielectric susceptibility of deuteron glass cooled down in the external field and of deuteron glass cooled down without the external field differ under a certain temperature T_f, while the susceptibilities above that temperature are identical.
• In the field of incommensurate systems, the shape of NMR spectra in the immediate vicinity of paraelectric-incommensurate phase transition was defined for the first time and the influence of thermal fluctuations and defects was determined.
• In the research of liquid crystals, phase transitions and molecular configurations in submicron polymer-dispersed nematic microdroplets was determined.
• Using the methods of two-dimensional NMR spectroscopy of deuterium, the existence of deuterons jumping between two potential holes in hydrogen bonds O-D–O in deuteron glasses was directly proven for the first time.

In the field of quantum optics, the following achievements deserve a special mention:

• discovery of the pyroelectric effect in high-temperature superconductors,
• measurements of time-resolved photorefractive effect in ferroelectric optical memory elements of the KnbO₃ type,
• research of the optical phase conjugation in nematic liquid crystals,
• research of hyper-Rayleigh scattering in nematic liquid crystals.

Research in biophysics brought the following important results:

• discovery of a connection between the permeability of membranes of corn root cells and the resilience of sprouting of different genotypes of corn at low temperatures,
• construction of a model for describing the penetration of liposomes into the skin,
• measurement of the spectrum of spin-labeled phorbol diesters, specifically bound to the protein kinase C receptor in the membrane in situ,
• tomography research of the possible uses of special contrasting agents, research of blood clot dissolution, and research of arthrosis.

In the scope of applied studies, it is worth mentioning the collaboration with Iskra, TOZD Hipot in the field of liquid-crystal displays, and Iskra TELO in the field of optical incremental encoders and displacement meters. A NMR minitomograph was also constructed and sent to Austria, Switzerland, Canada and Greece.

In 1990, some of the Department’s achievements were reached in the scope of the American-Yugoslav scientific and technical collaboration. Other collaborations included the Physics Department of Canada, the Institute of Low Temperature and Structural Research of the Polish Academy of Science, the Soviet Academy of Science, the Institute of Experimental Physics of the Vienna University as well as institution from Germany, Switzerland, Italy, Greece etc.

Year 1991

In 1991, the following laboratories operated within the Department for Condensed Matter Physics:

• Nuclear Magnetic Resonance Laboratory,
• Biophysics Laboratory,
• Quantum Optics Laboratory,
• Dielectric Spectroscopy Laboratory,
• NMR Tomography Laboratory.

Three applied research groups operated within the Department:

• research group for the application of ferroelectrics,
• research group for the application of liquid crystals,
• research group for the utilization of NMR.

A special mention goes to the work done by the independent electron microscopy and surface physics laboratory.

In 1991, the focus was on the following subjects:

• research of disordered ferroelectrics as well as proton and deuteron glasses,
• research of incommensurate systems,
• research of polymer-dispersed liquid crystals as well as ferroelectric and antiferroelectric liquid crystals,
• research of new methods of double nuclear resonance and two-dimensional NMR spectroscopy,
• research of quantum optics,
• research of high-temperature superconductors and new carbon modification C₆₀,
• research of microstructure of thin layers and defects in crystals and tunnel microscopy,
• research of biophysics of membranes and tissues, especially of transport processes and reactions coupled with transport.

Some of the biggest achievements of 1991 were:

• measurement of the phason dispersion as a function of the external magnetic field in a Smectic-C* ferroelectric liquid crystal,
• first ever measurement of a phasal diagram of a ferroelectric liquid crystal as a function of the cell thickness and discovery of the existence of Lifshitz point at the crosspoint of Smectic-A, Smectic-C and Smectic-C* phases,
• use of NMR to determine molecular configuration of liquid crystals in submicron cylindrical cavities, polymer gels and aerogels,
• use of dielectric spectroscopy to determine phase diagrams and the AT-line in proton and deuteron glasses,
• use of 2D NMR spectroscopy to determine the influence of both thermal fluctuations as well as defects and impurities on the form of the NMR spectrum and on the T₁ and T₂ relaxation times.

The following successes must be noted in the fields of optical spectroscopy and quantum optics:

• research on high-temperature superconductors, which led to a successful discovery of nonlinear photon phenomena connected with polarons in these compounds,
• research on pyroelectric effect and ferroelectricity in YBaCuO and LaCuO,
• preparation of a compound synthesis based on C_60,
• development of a sub-picosecond laser using the pulse compression for time-resolved Raman spectroscopy,

• research on infrared and photoinduced absorption spectra in conductive polymers,
• measurement and description of the process of second-harmonic generation in liquid crystals, research of time-resolved photorefractive phenomenon in ferroelectric optical memory elements,
• measurement of the Rayleigh scattering in liquid crystals,
• measurement of phase conjugation in nematic liquid crystals.

The research on defects in crystals and on microstructure of thin layers led to the following achievements:

• Findings noted in discontinuous changes of modulation wave vector in Ta_1-xNb_xTe₄ (0 ≤ 1) crystals made it possible to interpret the interconnections between seemingly different structural phenomena in crystals TaTe₄ in NbTe₄ based on a series of incommensurate phases with long periods.
• A mathematical model describing the formation of no-defect zone was perfected in the scope of research of controlled introduction of defects in silicon semiconductor technologies.
• The newly acquired raster tunnel microscope the researcheres achieved atomic level of resolution on the surface of graphite and silicon crystals and multilayer transition-metal dichalcogenides.
• In the field of biophysical research, the following results are worth mentioning:
• New spin scavenger methods were developed to study the level of metabolism of free radicals, which are produced during the functioning of xenobiotics.
• A model was developed to describe the binding of carcinogen substances to the protein kinase C in the membrane in situ.
• A method was developed to study the transport of liposomes into the skin, which was on of the most effective methods at the time.
• Fluctuations of molecules in membranes were studied with the resolution of a couple of tenths of nanometer of the membrane depth.
• The influence of aluminium on the phase separation in membranes of mycorrhizal fungi was measured.

In the domain of applied research, the following achievements deserve a mention:

• development of volume-stabilised ferroelectric liquid-crystal cell, which has all the advantages of a surface-stabilised FE LC cell, but is mechanically stable and can be used for high-resolution LC screens,
• development of a NMR microtomograph, which enables inexpensive NMR imaging of smaller samples.

The Department collaborated with Iskra CEO, Iskra HIPOT and Iskra TELAVI, with Contrex, Elan, Plutal, Salonit, Titanium, University Medical Center and Zarja. They also worked with the international company L’Oreal in the field of liposome characterisation regarding the transport of active substances into the skin.

As in the previous years, the Department collaborated scientifically and professionally with several important universities and institutes from all over the world. The employees of the Department also published many scientific papers and articles. The Department participated in several international scientific and professional conferences. Notable success in scientific, professional and applied research of the Department led to many international cooperations.

Year 1992

In 1992, the research at the Department of condensed matter physics was implemented within the following laboratories:

• Nuclear Magnetic Resonance Laboratory,
• Biophysics Laboratory,
• Electron Paramagnetic Resonance Laboratory,
• Quantum Optics Laboratory,
• Dielectric Spectroscopy Laboratory,
• Liquid Crystals Application Laboratory,
• MR Tomography Laboratory.

There were still two applied research groups active within the Department:

• research group for the application of ferroelectrics,
• research group for the use of NMR.

Last but not least, research was also carried out in the independent electron and tunnel microscopy and surface physics laboratory.

The majority of the work within the Department were basic studies, performed in order to gain new knowledge of the microscopic nature and the dynamics of condensed matter. These findings were used as a basis for development of new materials and technologies, and for research on their possible applications in industry. The Department’s research programme mainly focused on disordered and partially ordered condensed matter. The researchers studied systems in the intermediate state between fully ordered crystals with translational periodicity and disordered liquids. Basic principles of the disordered or partially ordered condensed matter differ from the principles of ordered matter, and new basic insights were still being discovered. However, these systems belong to the area of physics responsible for the fastest developing technologies, such as nanoelectronics, microelectronics and optoelectronics. After the discovery of superconductive characteristics in ceramic materials, glasses and fullerenes, the importances of disordered systems increased even further.

The studies in 1992 were mostly focused on:

• research on ferroelectric and antiferroelectric liquid crystals in confined systems and on polymer-dispersed liquid crystals,
• research on incommensurate systems with perfect long-range order but without translational periodicity,
• research on dipolar and quadrupolar glasses as possible intermediaries between spin glasses, in which we encounter thermodynamic phase transitions, and ordinary glasses, which are metastable states,
• research on new materials based on C₆₀ and high-temperature superconductors,
• research on laser physics and quantum optics,
• research on membrane and tissue biophysics, focusing on transport processes and reactions coupled with transport,
• research in the domain of medical physics,
• research on microstructure of thin layers and structure of modulated crystals and surfaces.

The following research methods were used to conduct the above studies:

• one- and two-dimensional NMR,
• imaging and microscope imaging with MR,
• double nuclear resonance,
• electron paramagnetic resonance,
• dielectric spectroscopy,
• Raman spectroscopy,
• nonlinear optical spectroscopy and time-resolved optical spectroscopy,
• electron and tunnel microscopy and X-ray diffraction.

Among the most important achievements in 1992 we should mention:

• determination of the nature of the organic “ferromagnetic” TDAE-C₆₀, which has the highest so far known Curie temperature among organic systems,
• determination of the molecular dynamics of the C₆₀ plastic crystal, in which we encounter hexadecapole orientational long-range order under the T_c temperature, and glass-like state at the lowest temperatures,
• determination of the dynamics of deuteron “jumping” between the two equilibrium positions in hydrogen bonds of O-D—O in deuteron glasses using D2 exchange NMR,
• determination of the local atomic structure of the modulation wave in incommensurate systems with 2-, 4- and 6-component order parameter using the NMR,
• determination of relaxation spectra in proton and deuteron glasses using dielectric spectroscopy, which led to the discovery that the longest relaxation time in the spectrum behaves divergently in accordance with the Vogel-Fulcher law, which determines the static freezing temperature,
• determination of the influence of thermal fluctuations on the shape of NMR spectra in incommensurate systems,
• determination of spin-lattice relaxation due to the sliding of the modulation wave under the influence of external electric field in CDW systems,
• determination of natural phase transitions in antiferroelectrics of the order-disorder type: RbSCN, KSCN, NH₄SCN,
• determination of phase diagrams of nematic liquid crystals in microconfined liquid-crystal droplets,
• determination of phase diagram of ferroelectric liquid crystal as a function of the geometry expansion limit, i.e. as a function of the thickness of measuring cell,
• the first ever determination of the energy bands in the phason dispersion relation in a ferroelectric crystal in an external field, and the splitting of phason branch into optical and acoustical branch under the influence of a magnetic field perpendicular to the ferroelectric helix axis.

Research of ferroelectric liquid crystals led to the discovery of volume-stabilised ferroelectric liquid-crystal cells, which are mechanically stable and very fast. It was predicted that in the future, they could replace the surface-stabilised ferroelectric liquid-crystal cells, which were widely used at the time, but were mechanically quite sensitive and as such unsuitable for high-resolution TV screens. In collaboration with the Liquid Crystal Institute of Ohio the Department applied for patent protection in the USA.

There were also several noteworthy achievements in the field of magnetic resonance imaging:

• construction of a systematic approach to harmless and non-invasive diagnosis of muscle diseases,
• use of the MR imaging to study wrist joints and develop the technology for separation of different kinds of arthritis thanks to the possibility of early detection of inflammations,
• monitoring of denervation changes of hindlimb flexor muscles of rats using the imaging and proton MR spectroscopy, which led to the conclusion that many results in the literature were imperfectly interpreted,
• use of MR imaging to determine the relation between force and tiredness of extensor muscles in patients with radial nerve defect,
• discovery that the speed of blood clots dissolution depends on the transport of active ingredients into the clot, and that the “finger-like” structure of dissolution appears as a result of the porous (almost fractal) nature of the fibrin gel that the clot is made of,
• development of an imaging technique for spatial distribution of ¹⁷O isotope in the human brain in collaboration with the Department of Physiology and Neurosurgery of the University of Illinois in Chicago; all probes and other equipment were made in Ljubljana,
• microscope imaging of hydration of synthetic cement gels.

In the field of biophysics, the following important results are worth referring to:

• It was experimentally proven that in cell membranes of plants and fungi the column ratio between more ordered and less ordered regions changes in response to external influences, confirming the hypothesis that biological systems adapt to external circumstances so that they are always near phase transitions.
• The interactions between highly hydrophobic cells and membranes were studied thorouhly.
• New methods were developed to study membranes from the point of view of fluidity, order, and transport of molecules.

These studies led to collaboration with the French company L’Oreal in the field of liposome characterisation and transport of active ingredients into the skin.

In the field of optical spectroscopy and quantum optics, the following achievements must be noted:

• measurements of ultrafast electron dynamics in C₆₀,
• determination of connection between critical temperature and phonon frequencies of specific ions in high-temperature superconductors (HTS),
• determination of anharmonic oxygen vibrations in HTS,
• determination of nonequilibrium polarons in HTS,
• synthesis and characterisation of various new C₆₀ compounds, including polymers,
• invention of a chemical procedure for separation of fullerenes,
• determination of influence of interactions between a liquid crystal and a prepared surface on the scattering of light near the surface,
• research of orientational surface waves on the interface between liquid crystal and a solid surface,
• measurements of light frequency doubling in ferroelectric liquid crystals,
• studies of free-standing films in smectic liquid crystals.

Research in the field of microstructure of thin layers, surface structures, and modulated phases resulted in the following notable achievements:

• determination of the dependence between the nature of modulation and the concentration of the dopant (Ti or Zr) in partially substituted TaTe₄ and NbTe₄ crystals,
• construction of the model of structural distortions, which explained the sliding of the CDW in NbSe₃ crystals,
• explanation of the reasons for irregular fluctuations of “atomic roughness” of the surface of NbSe₂ crystals, discovered with tunnel microscopy.

As always, the Department successfully collaborated on the international level; 72 scientific and 20 technical papers were published, as well as 25 reports, 68 abstracts, 3 patents, 8 graduate degrees, 7 master’s theses, and 2 doctorates.

Year 1993

In 1993, the following laboratories operated within the Department for Condensed Matter Physics:

• Nuclear Magnetic Resonance Laboratory,
• Biophysics Laboratory,
• Electron Paramagnetic Resonance Laboratory,
• Quantum Optics Laboratory,
• Dielectric Spectroscopy Laboratory,
• Liquid Crystals Application Laboratory,
• MR Tomography Laboratory.

Two applied research groups were still active within the Department:

• research group for the application of ferroelectrics,
• research group for the utilisation of NMR.

Last but not least, the work of the independent electron and tunnel microscopy and surface physics laboratory should also be noted.

In 1993, most of the studies involved:

• research on ferroelectric and antiferroelectric liquid crystals in external electric and magnetic fields and in spatially limited systems,
• research on polymer dispersed liquid crystals and composite liquid crystal-gel materials,
• research on incommensurate systems with perfect long-range order but without translational periodicity, which are the intermediate state between crystals and amorphous matter,
• research on dipolar and quadrupolar structural glasses, which are the intermediate state between spin glasses with equilibrium phase transition and regular glasses, which are metastable states,
• research on new materials based on C₆₀,
• research on high-temperature superconductors,
• research on laser physics and quantum optics,
• research on biophysics of membranes and tissues focused mostly on transport processes and medical physics,
• research on microstructure of thin layers and structure of modulated crystals and surfaces – the beginning of research on nanostructures and the possibility of data writing with nanostructure resolution.

The following research methods were used in the above mentioned studies:

• one and two-dimensional NMR,
• imaging and microscope imaging with magnetic resonance in high and low magnetic fields,
• double nuclear resonance,
• nuclear quadrupole resonance,
• electron paramagnetic resonance,
• dielectric spectroscopy,
• measurements of heat capacity,
• Raman scattering,
• Rayleigh spectroscopy,
• nonlinear optical spectroscopy and time-resolved optical spectroscopy,
• electron microscopy and x-ray diffraction,
• tunnel microscopy.

Among the most important achievements of 1993 are:

• development of a new method for determining and analysing dielectric relaxation spectra,
• determination of the AT line in phase diagram of (RB)_1-x(ND₄)_xD₂PO₄ deuteron glass, which proves that in such systems we encounter equilibrium phase transition from ergodic glass phase to non-ergodic glass phase,
• discovery of gapless phason elementary excitation in antiferroelectric liquid crystal with non-elastic laser-light scattering,
• discovery of soliton elementary excitations,
• discovery of optical and acoustic phasons separated by energy gap in the dynamic of ferroelectric liquid crystals in transversal external magnetic field,
• determination of phasal diagram of ferroelectric liquid crystals in limited geometry, and determination of soliton-like dynamics of these systems,
• determination of molecular order and structure of dispersed nematic liquid-crystal microdroplets in cylindrical cavities,
• determination of the nature of modulation waves in triple incommensurate modulated proustite (Ag₃AsS₃) crystal,
• determination of the nature of phase transition in TDAE-C₆₀ using the electron paramagnetic resonance in zero or very low external magnetic field.

The following achievements in the nuclear resonance imaging also deserve a mention:

• development of a new MR method of microimaging of electric currents that was used on biological systems,
• development of a new method for measurement of flow and self-diffusion of molecules, based on NMR imaging in a low magnetic field.

In the field of electron paramagnetic resonance and biophysics research, the following achievements are worth referring to:

• development of new methods to determine and evaluate the time development of concentration profiles of molecules penetrating into the skin,
• development of a new approach for research of membranes of plant tissues in situ.

The following achievements must be underlined in the field of optical spectroscopy and quantum optics:

• measurement of time-dependence of doubling of light frequency in ferroelectric liquid-crystals in alternating electric current,
• research of isolator-metal transition induced with ultrashort laser light pulses in high-temperature superconductors,
• in the field of fullerene research, synthesis of TDAE-C₆₀ with transition into the magnetic phase at 24 K, which is the highest transition temperature measured so far in an organic ferromagnetic.

The studies on microstructure of thin layers, surface structure and modulated phases led to the following achievements:

• During the research of modification possibilities and nanostructure formation with a tunnel microscope, voltage pulses on NbSe₂ crystals induced craters with diameters as small as 5 nm.
• Equivalence and compatibility of different crystallographic methods for description of incommensurate systems were confirmed in model systems NbS₃ and Nb_xTa_1-xTe₄.
• In situ intercalation of silver during vapour deposition on to TaS₂, NbS₂ and NbSe₂ crystals was experimentally proven, as well as some changes in surface and crystalline structure and CDW phases due to intrecalated silver.

The following achievements are worth mentioning regarding the work of the Centre for Science and Technology in the field of application of liquid crystals:

• development of quick, bistable optical displays with high resolution based on volume-stabilised ferroelectric liquid crystals,
• a new concept of multi-level controlling of liquid-crystal optical modulators, which allowed for a significantly shorter switching time and enabled the construction of automatic LC safety goggles for welders with much better characteristics than the previous models,
• a new technology of magnetic labelling of skis, which allowed the manufacturer to computer-control the manufacturing process.

As in previous years, the studies implemented by the Department were realised in collaboration with numerous reputable international institutions.

In 1993, 63 scientific papers were written, 12 technical papers, and 6 popular science articles; 25 reports were published, as well as 92 abstracts, 3 graduation theses, 5 master theses, and 5 doctorates.

Year 1994

In 1994, the research in the Department of Condensed Matter Physics was conducted in the following laboratories:

• Nuclear Magnetic Resonance Laboratory,
• Biophysics Laboratory,
• Electron Paramagnetic Resonance Laboratory,
• Quantum Optics Laboratory,
• Dielectric Spectroscopy Laboratory,
• Liquid Crystal Application Laboratory,
• MR Tomography Laboratory.

The Department still supported two applied research groups:

• research group for application of ferroelectrics,
• research group for the use of NMR.

The work within the independent laboratory for electron and tunnel microscopy and surface physics also deserves a mention.

The Centre of Science and Technology also operated in the scope of the Department, offering infrastructural and technological support for the applied studies, which were realised in collaboration with the founding companies. The main focus of the work was microscopic research and research on condensed matter dynamics on atomic and molecular level.

The research programme was mostly focused on researching disordered and partly ordered condensed matter, namely:

• liquid crystals
• incommensurate systems,
• structural glasses and nanomaterials as well as other plastic and partially disordered crystals.

The main research subjects in the field of liquid crystals were:

• ferroelectric and antiferroelectric liquid crystals,
• microconfined liquid crystals and polymer dispersed liquid crystals,
• biophysics of membranes and tissues, especially liposomes physics and physics of transportation processes within membranes and tissues.

In the field of incommensurate systems, which represent the intermediate state between perfectly ordered crystals with translational periodicity and disordered amorphous matter, the studies were focused on:

• phason dynamics in one-dimensional modulated incommensurate systems,
• soliton density in two-dimensional modulated incommensurate systems,
• soliton density and dynamics of modulation waves in three-dimensional modulated incommensurate systems,
• microstructure and surfaces of modulated crystals.

In the scope of the studies of structural glasses, partially disordered glasses, and partially disordered crystals, the following research was carried out:

• research on dynamic characteristics of proton and deuteron glasses based on solid solutions of ferroelectric and antiferroelectric RbH₂AsO₄ and NH₄H₂AsO₄ crystals,
• research on quadrupole (KJ)_x(NH₄J)_1-x glasses,
• research on  dynamics in C₆₀, C₇₀, and TDAE-C₆₀, and other similar materials,
• research on laser materials.

The following research methods were used in the above mentioned studies:

• one- and two-dimensional NMR,
• double nuclear resonance,
• magnetic resonance imaging,
• nuclear quadrupole resonance,
• electron spin resonance at 35 GHz, 9 GHz, and in low-frequency region of 10–100 MHz,
• dielectric spectroscopy in the region from 10^-3 Hz to 10⁹ Hz,
• Raman scattering,
• Rayleigh spectroscopy, nonlinear optical spectroscopy, and time-resolved optical spectroscopy,
• electron microscopy and x-ray diffraction, atomic force microscopy, and
• tunnel microscopy.

Among the most important achievements in 1994 are:

• clarification of the C₆₀, C₇₀, and TDAE-C₆₀ plastic crystals dynamics,
• proof of the existence of glass phase in weakly disordered substitution systems, and the first experimental determination of dynamic freezing in deuteron glasses,
• experimental determination of the relation between symmetry breaking in ferroelectric liquid crystals in external fields and formation of Goldstone excitations, which re-establish the lost symmetry,
• proof of the relation between orientational and magnetic structure in organic magnet based on TDAE-C₆₀,
• the first image of a C₆₀ thin layer with atomic resolution, taken with the help of atomic force microscope,
• development of EPR method for studying the transport of liposome-encapsulated hydrophobic active ingredients into the skin,
• development of a new active electro-optical protective filter based on nematic liquid crystals, the characteristics and the speed of which far exceeded any other filter available on the European market at the time.

The following projects were successfully completed in the scope the the Centre for Science and Technology:

• “Big modular information LCD screen” in collaboration with Iskra HIPOT,
• “Active protective electro-optical filter” in collaboration with Iskra Telo,
• “High-pressure gas light sources” in collaboration with Iskra Vega, Iskra SEM and VCS,
• “Communication unit for radio frequency identification of labelled objects” in collaboration with Iskra Mehanizmi,
• “Magnetic labelling of skis” in collaboration with Elan.

In 1994, the researchers at the Department for condensed matter physics published 73 scientific papers, 7 technical papers, 4 popular science papers, 49 reports, 92 abstracts, as well as 10 graduate theses, 6 master’s theses and 8 doctorates.