A5075495256- 2D Materials and Applications
- Organic and Molecular Conductors Research
- Iron-based superconductors research
- Quantum Mechanics and Applications
- Physics of Superconductivity and Magnetism
- Topological Materials and Phenomena
- Quantum Information and Cryptography
- Advanced Thermodynamics and Statistical Mechanics
- Chalcogenide Semiconductor Thin Films
- Advanced Condensed Matter Physics
- Quantum and electron transport phenomena
- Solid-state spectroscopy and crystallography
- Perovskite Materials and Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Spectroscopy and Quantum Chemical Studies
- Mechanical and Optical Resonators
- High-pressure geophysics and materials
- Advanced Chemical Physics Studies
- Electronic and Structural Properties of Oxides
- Quantum, superfluid, helium dynamics
- Molecular Junctions and Nanostructures
- Quantum Electrodynamics and Casimir Effect
- Magnetic and transport properties of perovskites and related materials
- Advanced NMR Techniques and Applications
- Rare-earth and actinide compounds
University of Amsterdam
2015-2024
Delta Institute for Theoretical Physics
2015-2023
Université Paris 1 Panthéon-Sorbonne
2023
Czech Academy of Sciences, Institute of Physics
2018-2022
Centrum Wiskunde & Informatica
2020-2022
QuSoft
2019-2022
University of California, Berkeley
2015-2016
Argonne National Laboratory
2011-2015
University of Bristol
2013-2015
University of Cambridge
2008-2011
The celebrated ``tenfold way'' provides a scheme for categorizing general topological states of matter, but it does not take into account the crystal symmetries that always exist in real materials. A new method extends this organization to allow categorization all topologically distinct electronic band structures materials with only any number physically relevant dimensions.
Topological edge modes are excitations that localized at the materials' edges and yet characterized by a topological invariant defined in bulk. Such bulk-edge correspondence has enabled creation of robust electronic, electromagnetic mechanical transport properties across wide range systems, from cold atoms to metamaterials, active matter geophysical flows. Recently, advent non-Hermitian systems---wherein energy is not conserved---has sparked considerable theoretical advances. In particular,...
Bose condensation has shaped our understanding of macroscopic quantum phenomena, having been realized in superconductors, atomic gases, and liquid helium. Excitons are bosons that have predicted to condense into either a superfluid or an insulating electronic crystal. Using the recently developed technique momentum-resolved electron energy-loss spectroscopy (M-EELS), we studied collective modes transition metal dichalcogenide semimetal 1T-TiSe2 Near phase-transition temperature (190 kelvin),...
The competition between proximate electronic phases produces a complex phenomenology in strongly correlated systems. In particular, fluctuations associated with periodic charge or spin modulations, known as density waves, may lead to exotic superconductivity several materials. However, waves have been difficult isolate the presence of chemical disorder, and suspected causal link competing wave orders high temperature is not understood. Here we use scanning tunneling microscopy image...
A charge-density wave (CDW) state has a broken symmetry described by complex order parameter with an amplitude and phase. The conventional view, based on clean, weak-coupling systems, is that finite long-range phase coherence set in simultaneously at the CDW transition temperature T$_{cdw}$. Here we investigate, using photoemission, X-ray scattering scanning tunneling microscopy, canonical compound 2H-NbSe$_2$ intercalated Mn Co, show view untenable. We find that, either high or large...
In charge ordered materials such as the transition-metal dichalcogenides, strong coupling between lattice modes and charges offers an excellent opportunity for novel phases unconventional forms of superconductivity to arise. One material, ${\text{TiSe}}_{2}$, has recently been found superconduct under pressure [A. F. Kusmartseva, B. Sipos, H. Berger, L. Forr\'o, E. Tuti\ifmmode \check{s}\else \v{s}\fi{}, Phys. Rev. Lett. 103, 236401 (2009)]. This finding cannot be explained simply...
Perhaps the most important aspect of symmetry in physics is idea that a state does not need to have same symmetries as theory describes it. This phenomenon known spontaneous breaking. In these lecture notes, starting from careful definition physics, we introduce breaking and its consequences. Emphasis placed on singular limits, showing reality even small-sized systems. Topics covered include Nambu-Goldstone modes, quantum corrections, phase transitions, topological defects gauge fields. We...
Niobium diselenide has long served as a prototype of two-dimensional charge ordering, believed to arise from an instability the electronic structure analogous one-dimensional Peierls mechanism. Despite this, various anomalous properties have recently been identified experimentally which cannot be explained by Peierls-like weak-coupling theories. We consider instead model with strong electron-phonon coupling, taking into account both full momentum and orbital dependence coupling matrix...
Significance Charge density waves (CDWs) are simple periodic reorganizations of charge in a crystal, and yet they still poorly understood continue to bear surprises. External perturbations, such as strain or pressure, can principle push CDW phase into different ordering geometry. However, engineering this type quantum criticality has been experimentally challenging. Here, we implement method for straining bulk materials. By applying it 2H -NbSe 2 , prototypical system studied decades,...
Time-resolved photoemission and optical experiments reveal a dynamical slowing down in the recovery of charge density wave (CDW) 1T-TiSe2 following perturbation by femtosecond laser pulse. This behavior correlates with switching dominant coherent phonon oscillations related to crystal lattice. The work sheds light on long standing question exciton- lattice-driven order this complex system.
Establishing the nature of ground state Heisenberg antiferromagnet (HAFM) on kagome lattice is well-known to be a prohibitively difficult problem for classical computers. Here, we give detailed proposal variational quantum eigensolver (VQE) intending solve this physical computer. At same time, VQE constitutes an explicit experimental showing useful advantage noisy intermediate-scale devices because its natural hardware compatibility. We classically emulate noiseless and computers with either...
Quantum criticality is a central concept in condensed matter physics, but the direct observation of quantum critical fluctuations has remained elusive. Here we present an X-ray diffraction study charge density wave (CDW) 2 H -NbSe at high pressure and low temperature, where observe broad regime order parameter that are controlled by proximity to point. X-rays can track CDW despite fact shrouded inside superconducting phase; contrast transport probes, allow measurement order. Concurrent...
It was recently discovered that the low-temperature, charge-ordered phase of $1T\mathrm{\text{\ensuremath{-}}}{\mathrm{TiSe}}_{2}$ has a chiral character. This unexpected chirality in system described by scalar order parameter could be explained model where emergence relative shifts between three charge density wave components breaks inversion symmetry lattice. Here, we present experimental evidence for sequence transitions predicted theory, going from disorder to nonchiral and finally...
In the presence of multiple bands, well-known electronic instabilities may acquire new complexity. While multiband superconductivity is subject extensive studies, possibility charge density waves (CDWs) has been largely ignored so far. Here, combining energy dependent scanning tunnelling microscopy (STM) topography with a simple model modulations and self-consistent calculation CDW gap, we find evidence for in 2H-NbSe2. This not only involves opening gap on inner band around K-point, but...
The inability of Schrödinger’s unitary time evolution to describe the measurement a quantum state remains central foundational problem. It was recently suggested that unitarity Schrödinger dynamics can be spontaneously broken, resulting in as an emergent phenomenon thermodynamic limit. Here, we introduce family models for spontaneous violation apply generic initial superpositions over arbitrarily many states, using either single or multiple state-independent stochastic components. Crucially,...
We report measurements of anisotropic triple-$q$ charge density wave (CDW) fluctuations in the transition metal dichalcogenide 1$T$-TiSe$_2$ over a large volume reciprocal space with X-ray diffuse scattering. Above temperature, $T_{\text{CDW}}$, out-of-plane scattering is characterized by rod-like structures which indicate that CDW neighboring layers are largely decoupled. In addition, in-plane marked ellipses reveal anisotropic. Our analysis line shapes and orientations suggests three...
We investigate the dispersion of charge carrier plasmon in three prototypical charge-density wave bearing transition-metal dichalcogenides $2H\mathrm{\text{\ensuremath{-}}}{\mathrm{TaSe}}_{2}$, $2H\mathrm{\text{\ensuremath{-}}}{\mathrm{TaS}}_{2}$, and $2H\mathrm{\text{\ensuremath{-}}}{\mathrm{NbSe}}_{2}$ employing electron energy-loss spectroscopy. For all compounds is found to be negative for small momentum transfers. This contrast with generic behavior observed simple metals as well...
Helical arrangements of spins are common among magnetic materials. The first material to harbor a corkscrew pattern charge density, on the other hand, was discovered only very recently. nature order parameter is key relevance, since rotating vector around any propagation trivially yields helical pattern. In contrast, purely scalar density cannot straightforwardly support chiral state. Here we use Landau analysis resolve this paradox, and show that may be understood as form orbital ordering....
Recently there has been a renewed interest in the charge density wave transition of TiSe2, fuelled by possibility that this may be driven formation an excitonic insulator or even condensate. We show here recent ARPES measurements on TiSe2 can also interpreted terms alternative scenario, which is due to combination Jahn-Teller effects and exciton formation. The hybrid exciton-phonons cause CDW interpolate between purely structural electronic type transition. Above temperature, electron-phonon...
We develop in detail a model of the charge order ${\mathrm{NbSe}}_{2}$ deriving from strong electron-phonon coupling dependent on ingoing and outgoing electron momenta as well electronic orbitals scattered between. Including both dependencies allows us to reproduce full range available experimental observations this material. The stability experimentally-observed charge-ordered geometries (1Q 3Q) is studied within function temperature uniaxial strain. It found that small amount bulk strain...
SrMnSb _2 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi /><mml:mn>2</mml:mn></mml:msub></mml:math> is suggested to be a magnetic topological semimetal. It contains square, 2D Sb planes with non-symmorphic crystal symmetries that could protect band crossings, offering the possibility of quasi-2D, robust Dirac semi-metal in form stable, bulk (3D) crystal. Here, we report combined and comprehensive experimental theoretical investigation electronic...