A5024948946- Topological Materials and Phenomena
- Quantum and electron transport phenomena
- Graphene research and applications
- Quantum many-body systems
- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Cold Atom Physics and Bose-Einstein Condensates
- 2D Materials and Applications
- Iron-based superconductors research
- Quantum, superfluid, helium dynamics
- Rare-earth and actinide compounds
- Quantum Computing Algorithms and Architecture
- Atomic and Subatomic Physics Research
- Quantum Information and Cryptography
- Magnetic properties of thin films
- Algebraic structures and combinatorial models
- Electronic and Structural Properties of Oxides
- Advanced Thermodynamics and Statistical Mechanics
- Advanced Physical and Chemical Molecular Interactions
- Advanced Chemical Physics Studies
- Catalysis and Oxidation Reactions
- History and advancements in chemistry
- Quantum Mechanics and Non-Hermitian Physics
- Topological and Geometric Data Analysis
- High-pressure geophysics and materials
Princeton University
2016-2025
Donostia International Physics Center
2017-2025
Ikerbasque
2021-2024
Czech Academy of Sciences, Institute of Physics
2024
University of Chinese Academy of Sciences
2024
Chinese Academy of Sciences
2024
Hong Kong University of Science and Technology
2024
University of Hong Kong
2024
Massachusetts Institute of Technology
2001-2023
Max Planck Institute of Microstructure Physics
2018-2022
We show that the quantum spin Hall (QSH) effect, a state of matter with topological properties distinct from those conventional insulators, can be realized in mercury telluride–cadmium telluride semiconductor wells. When thickness well is varied, electronic changes normal to an “inverted” type at critical d c . this transition phase between insulating and exhibiting QSH effect single pair helical edge states. also discuss methods for experimental detection effect.
The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. existence the effect requires breaking time reversal symmetry caused by an external magnetic field. In this work, we predict quantized spin in absence any field, where intrinsic conductance units $2\frac{e}{4\ensuremath{\pi}}$. degenerate Landau levels are created spin-orbit coupling conventional semiconductors presence strain gradient. This new has many correlated...
Majorana fermions are predicted to localize at the edge of a topological superconductor, state matter that can form when ferromagnetic system is placed in proximity conventional superconductor with strong spin-orbit interaction. With goal realizing one-dimensional we have fabricated iron (Fe) atomic chains on surface superconducting lead (Pb). Using high-resolution spectroscopic imaging techniques, show onset superconductivity, which gaps electronic density states bulk Fe chains, accompanied...
Based on first-principle calculations, we show that a family of nonmagnetic materials including TaAs, TaP, NbAs, and NbP are Weyl semimetals (WSM) without inversion centers. We find twelve pairs points in the whole Brillouin zone (BZ) for each them. In absence spin-orbit coupling (SOC), band inversions mirror-invariant planes lead to gapless nodal rings energy-momentum dispersion. The strong SOC these then opens full gaps mirror planes, generating nonzero Chern numbers off planes. resulting...
We extend the theory of dipole moments in crystalline insulators to higher multipole moments. In this paper, we expand great detail presented Ref. 1, and it cover associated topological pumping phenomena, a novel class 3D insulator with chiral hinge states. quantum-mechanical insulators, bulk manifest themselves by presence boundary-localized lower dimension, exact correspondence electromagnetic classical continuous dielectrics. certain symmetries, these are quantized, their boundary...
In quantum field theory, we learn that fermions come in three varieties: Majorana, Weyl, and Dirac. Here show solid state systems this classification is incomplete find several additional types of crystal symmetry-protected free fermionic excitations . We exhaustively classify linear quadratic 3-, 6- 8- band crossings stabilized by space group symmetries with spin-orbit coupling time-reversal symmetry. Several distinct arise, differentiated their degeneracies at along high symmetry points,...
Corner-dwelling topological states Computing the electric polarization of a crystal is surprisingly tricky, but it can be tackled with help concept, so-called Berry phase. Extensions to higher multiple moments, such as quadrupole and octupole, are even trickier. Benalcazar et al. built theoretical framework for dealing these moments in certain types solids. In presence some crystalline symmetries, moment quantized, corners system play host fractionally charged, topologically protected...
We introduce a new expression for the Z2 topological invariant of band insulators using non- Abelian Berry's connection. Our can identify nature general insulator without any gauge fixing problems that plague concrete implementation previous invariants. The be derived from "partner switching" Wannier function center during time reversal pumping and is thus equivalent to proposed by Kane Mele.
The edge states of the recently proposed quantum spin Hall systems constitute a new symmetry class one-dimensional liquids dubbed ``helical liquid'', where orientation is determined by direction electron motion. We prove no-go theorem which that helical liquid with an odd number components cannot be constructed in purely 1D lattice system. In components, uniform gap ground state can appear when time-reversal (TR) spontaneously broken interactions. On other hand, correlated two-particle...
Three-dimensional topological (crystalline) insulators are materials with an insulating bulk, but conducting surface states which topologically protected by time-reversal (or spatial) symmetries. Here, we extend the notion of three-dimensional to systems that host no gapless states, exhibit hinge states. Their character is spatio-temporal symmetries, present two cases: (1) Chiral higher-order combination and a four-fold rotation symmetry. chiral modes bulk topology $\mathbb{Z}_2$-classified....
We propose an easy-to-build easy-to-detect scheme for realizing Majorana fermions at the ends of a chain magnetic atoms on surface superconductor. Model calculations show that such chains can be easily tuned between trivial and topological ground state. In latter, spatial resolved spectroscopy used to probe fermion end states. Decoupled bound states form even in short consisting only tens atoms. scanning tunneling microscopy as ideal technique fabricate systems their properties.
We perform a complete classification of two-band $\bk\cdot\mathbf{p}$ theories at band crossing points in 3D semimetals with $n$-fold rotation symmetry and broken time-reversal symmetry. Using this classification, we show the existence new topological characterized by $C_{4,6}$-protected double-Weyl nodes quadratic in-plane (along $k_{x,y}$) dispersion or $C_6$-protected triple-Weyl cubic dispersion. apply theory to ferromagnet HgCr$_2$Se$_4$ confirm it is metal protected $C_4$ Furthermore,...
Spin-orbit coupled systems generally break the spin rotation symmetry. However, for a model with equal Rashba and Dresselhauss coupling constants, [110] model, new type of SU(2) symmetry is discovered. This robust against spin-independent disorder interactions generated by operators whose wave vector depends on strength. It renders lifetime infinite at this vector, giving rise to persistent helix. We obtain fluctuation dynamics at, away from, point suggest experiments observe
We study translationally-invariant insulators with inversion symmetry that fall outside the established classification of topological insulators. These are not required to have gapless boundary modes in energy spectrum. However, they do exhibit protected entanglement spectrum localized on cut between two entangled regions. Their entropy cannot be made vanish adiabatically, and hence can called topological. There is a direct connection eigenvalues band structure mid-gap states The levels...
We show that the electronic structure of low-energy bands in small angle-twisted bilayer graphene consists a series semimetallic and topological phases. In particular, we are able to prove, using an approximate particle-hole symmetry, gapped set exist around all magic angles have nontrivial topology stabilized by magnetic provided band gaps appear at fillings ±4 electrons per moiré unit cell. The index is given as winding number (a Z number) Wilson loop Brillouin zone. Furthermore, also...
We survey various quantized bulk physical observables in two- and three-dimensional topological band insulators invariant under translational symmetry crystallographic point group symmetries (PGS). In two-dimensional insulators, we show that: (i) the Chern number of a $C_n$-invariant insulator can be determined, up to multiple $n$, by evaluating eigenvalues operators at high-symmetry points Brillouin zone; (ii) is also $C_n$ eigenvalue Slater determinant noninteracting many-body system (iii)...
Based on the ab initio calculations, we show that MoTe_{2}, in its low-temperature orthorhombic structure characterized by an x-ray diffraction study at 100 K, realizes 4 type-II Weyl points between Nth and (N+1)th bands, where N is total number of valence electrons per unit cell. Other WPs nodal lines different other bands also appear close to Fermi level due a complex topological band structure. We predict series strain-driven phase transitions this compound, opening wide range possible...