Main activities of Department of Dielectrics cover experimental and theoretical investigations of high-permittivity insulators like liquid crystals, ferroelectrics, multiferroics, piezoelectrics, semiconductor nanostructures, and low-loss materials.
- Complex layered chalcogenides
- Dielectric and IR spectroscopy
- Liquid crystals
- Light and neutron scattering
- Solid-state materials science
- Theory and simulations
- THz science and technology
- Topological structures
The most significant fresh scientific results of our deparment are listed in the section Highlights.
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Liquid crystals that change colour using only light
Research by Alexej Bubnov and Sergei Mironov on "Optical tuning of a 3D blue phase photonic crystal with chiral photosensitive dopants", recently published in Photonics Research, has been featured as a recommended highlight by the prominent optics portal, Researching.cn.
“What if a crystal could change the way it interacts with light simply by shining another light on it: without electricity, moving parts, or changing its structure?” This captivating question opens a recent feature on the prominent optics portal Researching.cn [1], which recently spotlighted a groundbreaking study co-authored by our colleagues.
The internationally featured research, published in Photonics Research [2], represents a major leap forward in optical engineering. A collaborative team from the Czech Academy of Sciences and the Military University of Technology in Poland, including Eva Oton, Martin Cigl, Przemysław Morawiak, Karel Pomeisl, Sergei Mironov, Wiktor Piecek, and Alexej Bubnov, has successfully developed a new type of all-optically tunable 3D photonic crystal.
The magic of blue phase liquid crystals
The team's research targets on Blue Phase liquid crystals. As the featured article notes,
these materials are remarkable because their molecules spontaneously self-assemble into
a "highly ordered 3D structure with a periodicity comparable to the wavelength of visible light" [1].
This unique architecture essentially turns them into 3D photonic crystals capable of selectively reflecting specific colours.
But the real breakthrough lies in how the team learned to control this colour reflection.
To achieve this, the researchers synthesized custom-designed, light-responsive molecules and integrated them into the crystal. The resulting mechanism is as elegant as it is effective:
"When illuminated with light of different wavelengths, these molecules reversibly change their shape, causing the microscopic crystal lattice to expand or contract. As a result, the crystal's photonic bandgap (its characteristic reflected colour) can be tuned in a precise and completely reversible way using light alone" [1].
Highlighted figure that presents phototunability of a Blue Phase I (BP) with chiral photosensitive dopants:
(a) monocrystalline crystal lattice enlargement with light in BP-a + X3,
(b) the structure shrinking under light in BP-b + X3, and
(c) reflection spectra showing progressive lattice enlargement and
shrinkage switches achieved with all the prepared blue phase monocrystals of different (200) and (110) lattice planes and
dopant formulations [2].
A monocrystalline breakthrough
Previous attempts to create light-responsive Blue Phase systems often resulted in polycrystalline structures, which suffered from light scattering and optical haze. The new study overcomes this barrier entirely. The media highlight emphasizes that one of the team's major achievements is that "the tuning process occurs without disrupting the crystal's highly ordered 3D structure" [1]. By developing large monocrystalline photonic crystals, the team ensured exceptional optical quality and stability throughout repeated switching cycles.
Shaping the future of optical devices
The implications of this work extend far beyond the laboratory. By eliminating the need for electrical fields or physical contact, this technology paves the way for a new era of devices.
"The ability to control the optical properties of a photonic crystal using only light represents an important step toward a new generation of energy-efficient photonic devices... these materials could be used for compact tunable optical filters, adaptive optics, holographic devices, optical communications, and future integrated photonic circuits" [1].
This research based on a fruitful collaboration of the teams from the Institute of Physics of the Czech Academy of Sciences and Military University of Technology perfectly demonstrates how advanced molecular engineering can transform soft materials into intelligent, dynamically programmable devices.
References
[1] Researching.cn Editorial Team,
Teaching a Crystal to Change Color Using Only Light,
Researching.cn (2026).
[2] E. Oton, M. Cigl, P. Morawiak, K. Pomeisl, S. Mironov, W. Piecek, and A. Bubnov,
Optical tuning of a 3D blue phase photonic crystal with chiral photosensitive dopants,
Photonics Research 14, 3437 (2026).
The man behind the scenes of Czechia's IYPT success
Gold medals are not won overnight. They are the result of months of patient preparation, rigorous training, and tireless mentorship. One of the driving forces behind the scenes is Hynek Němec, who helped guide the Czech team to a historic gold medal at the 2026 International Young Physicists' Tournament, ending a 28-year wait for the top podium spot.
Breaking a 28-year drought in Zurich
This year, the international round of the 39th annual
International Young Physicists' Tournament (IYPT)
took place from July 5–12, 2026, in Zurich, Switzerland. The Czech Republic was represented by a five-member team:
- Lukáš Franta (Captain; Ch. Doppler Grammar School, Prague)
- Kryštof Basista (J. Kainar Grammar School, Hlučín)
- Michal Fišer (VOŠ and SPŠE Plzeň)
- Daniel Jedlička (VOŠ and SPŠE Plzeň)
- Daniel Švaňa (Ch. Doppler Grammar School, Prague)
(Studio 6, July 15, 2026; Snídaně s Novou, July 20, 2026)
From golden student to mentor
Hynek Němec knows exactly what it takes to stand on the IYPT podium.
He was a team member during the "golden era" of the Czech team in the late 1990s,
competing successfully as an active participant:
- IYPT 1996 (Tskhaltubo, Georgia): The Czech team won gold. Alongside Hynek Němec, the team included captain Karel Výborný, Petr Holzhauser, Tomáš Ostatnický, and Michael Prouza (led by Zdeněk Kluiber and Jiří Hlinka).
- IYPT 1997 (Cheb, Czech Republic): Hynek Němec stepped up as captain and led the team to another gold medal. He competed alongside Petr Chaloupka, Libor Inovecký, Filip Matějka, and Petr Luner (led by Zdeněk Kluiber and Petr Pavlíček).
(Novinky.cz, 14.7.2026)
The power of preparation and teamwork
The key to success in this grueling tournament is teamwork—not just among the students on stage,
but also with the organizers and mentors guiding them behind the scenes.
Throughout their intensive, year-long preparation,
the 2026 team relied heavily on detailed feedback from members of the
Czech IYPT Committee and its collaborators.
Beyond his direct coaching, Hynek is a driving force behind initiatives designed to recruit and nurture new talents.
He helps to organize events for incoming participants, including introductory workshops, the signature
VYDRA
training course, and a final symposium (which took a brief pause this year) where students present their findings and
defend them before expert physicists.
The hope is that this historic 2026 gold medal, building on the silver successes of recent years,
will inspire the next generation of young minds to take up the physics challenge.
| Year | Host location | Result / Medal |
|---|---|---|
| 1993 | Protvino, Russia | 🥈 Silver |
| 1994 | Groningen, Netherlands | 🥇 Gold |
| 1995 | Spała, Poland | 🥈 Silver |
| 1996 | Kutaisi, Georgia | 🥇 Gold |
| 1997 | Cheb, Czech Republic | 🥇 Gold |
| 1998 | Donaueschingen, Germany | 🥇 Gold |
| 1999 | Vienna, Austria | 🥉 Bronze |
| 2000 | Budapest, Hungary | 🥉 Bronze |
| 2001 | Espoo, Finland | No Medal |
| 2002 | Odesa, Ukraine | 🥉 Bronze |
| 2003 | Uppsala, Sweden | 🥉 Bronze |
| 2004 | Brisbane, Australia | No Medal |
| 2005 | Winterthur, Switzerland | No Medal |
| 2006 | Bratislava, Slovakia | No Medal |
| 2007 | Seoul, South Korea | No Medal |
| 2008 | Trogir, Croatia | No Medal |
| 2009 | Tianjin, China | No Medal |
| 2010 | Vienna, Austria | No Medal |
| 2011 | Tehran, Iran | No Medal |
| 2012 | Bad Saulgau, Germany | No Medal |
| 2013 | Taipei, Taiwan | No Medal |
| 2014 | Shrewsbury, United Kingdom | No Medal |
| 2015 | Nakhon Ratchasima, Thailand | No Medal |
| 2016 | Yekaterinburg, Russia | No Medal |
| 2017 | Singapore | 🥈 Silver |
| 2018 | Beijing, China | 🥉 Bronze |
| 2019 | Warsaw, Poland | No Medal |
| 2020 | cancelled (COVID-19) | — |
| 2021 | Kutaisi, Georgia | No Medal |
| 2022 | Timișoara, Romania | 🥈 Silver |
| 2023 | Murree, Pakistan | 🥈 Silver |
| 2024 | Budapest, Hungary | No Medal |
| 2025 | Lund, Sweden | 🥉 Bronze |
| 2026 | Zurich, Switzerland | 🥇 Gold |
About the tournament:
The preparation of the
Young Physicists Tournament participants takes almost a year during
which the students have to solve 17 open-ended inquiry problems. Similarly as in the real-world scientific research,
they have to inspect problems from different points of view, to look for relevant information in literature,
to analyze data, to defend results obtained, etc. The competition itself consists in a model scientific discussion
about the achieved results, in which the teams alternate in three different roles:
presenting their solution of the problem, acting as an opponent, and evaluating solutions of the other teams.
The performance of the team in each role is evaluated by a jury which consists of real experts.
The tournament is thus a demanding competition not only for students but also for their teachers.
It exceeds common knowledge competitions – the aim is not only solving problems,
but especially the ability of critical thinking, presentation, and discussion of the results.
These are exactly the skills in the knowledge-based economics of the 21th century.
For this reason, it is strongly recommended in the outcomes of the project DIBALI
(Development of Inquiry Based Learning via IYPT) to support the competitions according to
their benefits rather than by the number of participants, and
to acknowledge the work of teachers preparing students for such demanding competitions with high added value.
(website of the competition: https://www.tmfcr.cz/)
Microwave varactor published in Nature Electronics
In collaboration with American colleagues, a new thin-film system (ATiO3)nAO
(where A = Ba0.45Sr0.55, n = 8–∞)
with a Ruddlesden-Popper crystal structure was prepared and characterized.
It exhibits an anomalously high electric-field-tunable permittivity and record-low microwave losses.
It can therefore be used as a varactor (an electric-field-tunable capacitor) in microwave devices
[F. Bergmann, M.R. Barone, Z. Tian, et al.
Breaking symmetry yields a low-loss out-of-plane tunable microwave dielectric,
Nature Electronics (2026)].
New layered material for microwave varactors
Future microwave devices should utilize components with low power consumption. This includes varactors, which are electrically tunable capacitors. S. Kamba’s group collaborated with their American colleagues on the development of a new layered material with a Ruddlesden-Popper crystal structure, which exhibits an anomalously high tunability of permittivity under an electric field and record-low microwave losses [Nature Electronics (2026)].
Thin films ATiO3)nAO
(where A = Ba0.45Sr0.55, n = 8–∞)
were prepared using molecular beam epitaxy (MBE) at Cornell University,
where the microstructure of the thin films was also characterized using STEM and XRD.
Microwave and dielectric properties were measured at NIST in Boulder.
The Czech group performed THz and infrared measurements and, based on these results,
explained the observed high tunability of permittivity by the high sensitivity of the ferroelectric soft phonon to
an electric field.
The low dielectric losses were explained by the absence of the central mode
(i.e., microwave and terahertz dielectric relaxation), which typically appears near the temperature of ferroelectric phase transitions.
In our thin films, this temperature was around 200 K, and therefore the central mode was not activated.
This paper, published in the journal Nature Electronics [1],
is the result of many years of collaboration between S. Kamba’s group at the FZU and Prof. Schlom at Cornell University.
In an earlier article published in Nature Materials [2],
we succeeded in preparing and characterizing a similar microwave material
(SrTiO3)5BaTiO3SrO,
which was tunable by an electric field in the plane of the layers.
The new thin films (ATiO3)nAO
are tunable perpendicular to the layer plane and can therefore be used to fabricate small,
highly tunable varactors with low microwave dielectric losses.
Figure: Schematic of the Ruddlesden-Popper crystal structures and reflection of an infrared beam from a thin film deposited on a DyScO3 substrate. Right: STEM image with atomic resolution..
[1] F. Bergmann, M.R. Barone, Z. Tian, A. Ross, G.H. Olsen, M.C. Papac, Samuel Freed, B.T. Bosworth, N.R. Jungwirth, E.J. Marksz, T.M. Karpisz, A.C. Stelson, N. Schnitzer, L. Bhatt, D. Sotir, A. Surampalli, V. Goian, C. Kadlec, A. Hansen, N. Rongitsch, D.A. Tenne, S. Kamba, D.A. Muller, I. Takeuchi, Long-Qing Chen, L.W. Martin, N.D. Orloff, and D.G. Schlom,
Breaking symmetry yields a low-loss out-of-plane tunable microwave dielectric, Nature Electronics (2026).
[2] N. M. Dawley, E.J. Marksz, A.M. Hagerstrom, G.H. Olsen, M.E. Holtz, V. Goian, C. Kadlec, J. Zhang, X. Lu, J.A. Drisko, R. Uecker, S. Ganschow, C.J. Long, J.C. Booth, S. Kamba, C.J. Fennie, D. A. Muller, N.D. Orloff, D.G. Schlom,
Targeted chemical pressure yields tuneable millimetre-wave dielectric, Nature Materials 19, 176 (2020).
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Pyramidal charged domain walls in ferroelectric BiFeO3
We uncover the physical origins of the enigmatic zigzag domain structure in the prototypical multiferroic material BiFeO3. Using phase-field simulations, we demonstrate that spatially-homogeneous defect charges result in domain structures that closely resemble those observed experimentally. The acquired understanding of the underlying physics of pyramidal-domain formation may enable the engineering of new materials with self-assembled domain structures. [Commun. Mater. 6, 161 (2025)].
We addressed a long-standing puzzle in ferroelectric research: the origin of unusual zigzag and pyramidal domain structures in the multiferroic material BiFeO3. These complex patterns had been observed experimentally for years, but their physical cause remained unclear. Using phase-field simulations within the Landau–Ginzburg–Devonshire framework, we demonstrated that they can naturally form when defect charges are distributed homogeneously in the crystal. The system compensates these charges by creating pyramid-like domains in which the polarization rotates to lower the overall energy. Our simulated patterns agree closely with transmission electron microscopy observations of BiFeO3 crystals from our colleagues at the University of Warwick, giving strong support to our model. Beyond solving a fundamental question, this insight has practical value. The pyramidal domains are highly regular and self-assembled with nanometer-scale periodicity, making them attractive for applications requiring precise ordering, such as optics or topological defect-based devices.
Phase-field simulations for a rhombohedral ferroelectric material:
a) 3D visualization of the wall surface.
b) Ferroelectric polarization visualized in the plane (-110).
c) Distance of the domain wall from the center of the charged layer measured along [111].
d) Deviation of the polarization from the pyramid’s axis.
Polarization is projected to two selected planes, color indicates polarization component perpendicular to [111] direction.
Red: positive, blue: negative, white: no deviation.
[1] P. Marton, M. Paściak, M. A. P. Gonçalves, O. Novák, J. Hlinka, R. Beanland, and M. Alexe, Pyramidal charged domain walls in ferroelectric BiFeO3, Commun. Mater. 6, 161 (2025).
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Phonon studies of the phase transition sequence in an antiferroelectric single crystal
The sequence of phase transitions in PbHf0.83Sn0.17O3 was studied using THz, far-infrared, and Raman spectroscopies.
These investigations revealed the complementary roles of polar and non-polar phonons in lattice dynamics,
establishing the sequence of transitions on cooling as PE → IM → AFE2 → AFE1
[J. Appl. Phys. 138, 104101 (2025)].
The investigation of Pb(Hf,Sn)O3 and the fundamental mechanism of its antiferroelectric properties help to advance in the field of materials for energy storage. This paper aims to better understand the lattice dynamics and the different phonons that drive the exotic phase transitions of this system, including an unknown intermediate phase at high temperatures.
The sequence of phase transitions in PbHf0.83Sn0.17O3 (PHS-17) has been studied by THz, far infrared, and Raman spectroscopies. Spectroscopic investigations revealed the complementary behaviour of both polar and non-polar phonons and their impact on the lattice dynamics, concluding that the sequence of phase transitions for PHS-17 on cooling is PE → IM → AFE2 → AFE1.
Symmetry analysis and optical observations revealed that the intermediate IM phase has plausible tetragonal symmetry and it is, driven by an polar instability from the center of the Brillouin zone. Domain dynamics suggests that the presence of Sn triggers the development of the IM phase with its distinctive tweed pattern. The overall transformation from the cubic paraelectric phase (PE) to the final antiferroelectric orthorhombic Pbam phase (AFE1) thus involves two middle phases that sequentially accommodate the shifts of Pb atoms and tilts of the oxygen octahedra. The Pb atom is more sensitive to the high temperature phase transitions through strong dielectric anomalies, while oxygen atoms are more significant in the AFE2 and AFE1 phases, where their antiferrodistortive modes become the main driving force.
Schematics of the phase transition sequence in antiferroelectric Pb(Hf0.83Sn0.17)O3.
[1] Anirudh K R, C. Milesi-Brault, C. Kadlec, D. Nuzhnyy, A. Majchrowski, M. Krupska-Klimczak, I. Jankowska-Sumara, and E. Buixaderas,
Phonon studies of the phase transition sequence in antiferroelectric single crystal of Pb(Hf0.83Sn0.17)O3,
J. Appl. Phys. 138, 104101 (2025).
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Breaking symmetry yields a low-loss out-of-plane tunable microwave dielectric
Nature Electronics (2026).
Controlling mixed Mo/MoS2 domains on Si by molecular beam epitaxy for the hydrogen evolution reaction
ACS Nano 20, 4479 (2026).
Switchable topological polar textures in freestanding ultrathin ferroelectric oxides
Nano Lett. 26, 5258 (2026).
Intertwined swirling polarization states in BaTiO3 with embedded BaZrO3 nanoregions
Phys. Rev. Lett. 136, 126201 (2026).
Accelerating the design of resorbable magnesium alloys: a machine learning approach to property prediction
Mater. Des. 266, 116060 (2026).
Optical tuning of a 3D blue phase photonic crystal with chiral photosensitive dopants
Photon. Res. 14, 3437 (2026).
Crystal-field-driven magnetoelectric coupling in the non-Kramers hexaaluminate PrMgAl11O19
J. Alloy. Compd. 1061, 187535 (2026).
Enhanced control of self-assembling and photoactive behaviour for lactic acid derivatives via lateral substitution in the vicinity of azobenzene moiety
J. Mol. Liq. 446, 129296 (2026).
Terahertz-field activation of polar skyrons
Nat. Commun. 16, 8994 (2025).
Establishing a pure antiferroelectric PbZrO3 phase through tensile epitaxial strain
Nat. Commun. 16, 6536 (2025).
Curvature-controlled polarization in adaptive ferroelectric membranes
Small, e06338 (2025)