A5056417959- Topological Materials and Phenomena
- Quantum and electron transport phenomena
- Quantum Mechanics and Non-Hermitian Physics
- Physics of Superconductivity and Magnetism
- Quantum many-body systems
- Graphene research and applications
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Condensed Matter Physics
- Quantum chaos and dynamical systems
- 2D Materials and Applications
- Advancements in Semiconductor Devices and Circuit Design
- Quantum, superfluid, helium dynamics
- Nonlinear Photonic Systems
- Algebraic structures and combinatorial models
- Electronic and Structural Properties of Oxides
- COVID-19 epidemiological studies
- Spectral Theory in Mathematical Physics
- Atomic and Subatomic Physics Research
- Photonic and Optical Devices
- Advanced Fiber Laser Technologies
- Magnetic properties of thin films
- Quantum Computing Algorithms and Architecture
- Quantum Information and Cryptography
- Evolution and Genetic Dynamics
- COVID-19 and Mental Health
Stockholm University
2016-2025
AlbaNova
2016-2025
Freie Universität Berlin
2012-2017
Max Planck Institute for the Physics of Complex Systems
2009-2013
Max Planck Society
2009-2011
Quantum systems that are coupled to an external bath can often be described in terms of a non-Hermitian effective Hamiltonian. In isolated with Hermitian Hamiltonians, topological aspects the band structure, and resulting phases, have been interest. The combination two concepts, i.e., properties open systems, leads qualitatively new effects. This review provides introduction these quantum mechanical concepts their classical analogs, discusses number applications ranging from metamaterials...
Non-Hermitian systems exhibit striking exceptions from the paradigmatic bulk-boundary correspondence, including failure of bulk Bloch band invariants in predicting boundary states and (dis)appearance at parameter values far those corresponding to gap closings periodic without boundaries. Here, we provide a comprehensive framework unravel this disparity based on notion biorthogonal quantum mechanics: While properties left right eigenstates modes are individually decoupled physics...
Topological insulators and their intriguing edge states can be understood in a single-particle picture as such exhaustively classified. Interactions significantly complicate this lead to entirely new insulating phases, with an altogether much richer less explored phenomenology. Most saliently, lattice generalizations of fractional quantum Hall states, dubbed Chern insulators, have recently been predicted stabilized by interactions within nearly dispersionless bands nonzero number, C....
We introduce and study a novel class of sensors whose sensitivity grows exponentially with the size device. Remarkably, this drastic enhancement does not rely on any fine-tuning, but is found to be stable phenomenon immune local perturbations. Specifically, physical mechanism behind striking intimately connected anomalous boundary conditions observed in non-Hermitian topological systems. outline concrete platforms for practical implementation these ranging from classical metamaterials...
Non-Hermitian Hamiltonians, which describe a wide range of dissipative systems, and higher-order topological phases, exhibit novel boundary states on corners hinges, comprise two areas intense current research. Here we investigate systems where these frontiers merge formulate generalized biorthogonal bulk-boundary correspondence, dictates the appearance modes at parameter values that are, in general, radically different from those mark phase transitions periodic systems. By analyzing...
Symmetry plays a paramount role for the classification of phases matter occurring in nature. Combining symmetry analysis with concepts from topology that allow us to identify global and robust physical properties, new quantum matter, such as topological insulators semimetals, have been discovered recent years. Here, authors analyze general exemplify importance symmetries dissipative counterparts semimetals non-Hermitian systems, thus introducing notion symmetry-protected nodal phases.
Abstract Despite notable scientific and medical advances, broader political, socioeconomic behavioural factors continue to undercut the response COVID-19 pandemic 1,2 . Here we convened, as part of this Delphi study, a diverse, multidisciplinary panel 386 academic, health, non-governmental organization, government other experts in from 112 countries territories recommend specific actions end persistent global threat public health. The developed set 41 consensus statements 57 recommendations...
A microscopic study of Coulomb interactions within a fractionally filled spin-polarized moir\'e flatband system shows that high temperature fractional Chern insulators can form in twisted bilayer graphene.
Remarkable recent experiments have observed fractional quantum anomalous Hall effects at zero field and unusually high temperatures in twisted semiconductor bilayer <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>t</a:mi><a:msub><a:mi>MoTe</a:mi><a:mn>2</a:mn></a:msub></a:mrow></a:math>, hence realizing the first genuine Chern insulators. Intriguing observations these experiments, such as absence of integer twist angles where a effect is observed, do however remain...
Lattice models forming bands with higher Chern number offer an intriguing possibility for new phases of matter no analogue in continuum Landau levels. Here, we establish the existence a bulk insulating states at fractional filling flat C = N > 1, recently proposed pyrochlore model strong spin-orbit coupling. In particular, find compelling evidence series stable ν 1/(2N + 1) fermions as well bosonic 1/(N 1). By examining topological ground state degeneracies and excitation structure...
Weyl semimetals are paradigmatic topological gapless phases in three dimensions. We here address the effect of disorder on charge transport semimetals. For a single node with energy at degeneracy point and without interactions, theory predicts existence critical strength beyond which density states takes nonzero value. Predictions for conductivity divergent, however. In this work, we present numerical study properties disordered cone zero energy. weak our results consistent renormalization...
Three-dimensional condensed matter incarnations of Weyl fermions generically have a tilted dispersion-in sharp contrast to their elusive high-energy relatives where tilt is forbidden by Lorentz invariance, and with the low-energy excitations two-dimensional graphene sheets either crystalline or particle-hole symmetry. Very recently, number materials (MoTe_{2}, LaAlGe, WTe_{2}) been identified as hosts so-called type-II whose dispersion so strongly that Fermi surface formed, whereby node...
The generic nature of band touching points in three-dimensional structures is at heart the rich phenomenology, topological stability and novel Fermi arc surface states associated with Weyl semimetals. Here we report on corresponding scenario emerging systems effectively described by non-Hermitian Hamiltonians. Remarkably, have touchings along one-dimensional closed contours forming exceptional rings links reciprocal space. Seifert surfaces support open "Fermi ribbons" where real part energy...
We devise a generic recipe for constructing $D$-dimensional lattice models whose $d$-dimensional boundary states, located on surfaces, hinges, corners, and so forth, can be obtained exactly. The solvability is rooted in the underlying structure as such does not depend fine tuning, allowing us to track their evolution throughout various phases across phase transitions. Most saliently, our provide ``boundary solvable'' examples of recently introduced higher-order topological phases. apply...
We calculate conductance and noise for quantum transport at the nodal point arbitrarily tilted anisotropic Dirac or Weyl cones. Tilted dispersions are generic in absence of certain discrete symmetries, such as particle-hole lattice group symmetries. Whereas anisotropy affects $g$, but leaves Fano factor $F$ (the ratio shot power current) unchanged, a tilt both $g$ $F$. Since is universal number many other situations, this finding remarkable. apply our general considerations to specific...
We analyze the entanglement spectrum of Laughlin states on torus and show that it is arranged in towers, each which generated by modes two spatially separated chiral edges. This structure present for all circumferences, allows a microscopic identification prominent features perturbing around thin limit.
Topology, the theory of global properties invariant under continuous deformation, has proven essential for understanding variety forms matter occurring in nature. Here, two paradigmatic concepts topology physics, namely, knots and topological energy bands, are brought together to introduce a form matter, best labeled as knotted non-Hermitian metals. Remarkably, terms accounting dissipative coupling system its environment crucial generic stability these exotic systems.
A large number of recent works point to the emergence intriguing analogs fractional quantum Hall states in lattice models due effective interactions nearly flat bands with Chern $C=1$. Here, we provide an intuitive and efficient construction almost dispersionless higher numbers. Inspired by physics multilayers pyrochlore-based transition-metal oxides, study a tight-binding model describing spin-orbit coupled electrons $N$ parallel kagome layers connected apical sites forming...
This paper proposes material junctions involving topological insulator materials as a natural and immediately experimentally available electronic platform to realize NH Weyl phases, an intriguing form of dissipative quantum matter without direct counterpart in closed systems.
We establish the appearance of a qualitatively new type spin liquid with emergent exceptional points when coupling to environment. consider an open system Kitaev honeycomb model generically coupled external In extended parameter regimes, Dirac Majorana fermions from original are split into Fermi arcs connecting them. glaring contrast gapless phase that requires time-reversal symmetry, this is stable against all perturbations. The also displays large sensitivity boundary conditions resulting...
The interplay between dissipation, topology and sensitivity to boundary conditions has recently attracted tremendous amounts of attention at the level effective non-Hermitian descriptions. Here we exactly solve a quantum mechanical Lindblad master equation describing dissipative topological Su-Schrieffer-Heeger (SSH) chain fermions for both open condition (OBC) periodic (PBC). We find that extreme on associated with skin effect is directly reflected in rapidities governing time evolution...
We explore anomalous skin effects at non-Hermitian impurities by studying their interplay with potential disorder and exactly solving a minimal lattice model. A striking feature of the solvable single-impurity model is that presence anisotropic hopping terms can induce scale-free accumulation all eigenstates opposite to bulk direction, although nonmonotonic behavior fine tuned further increasing such weakens eventually reverses effect. The disorder, however, qualitatively enriches this...
Nonuniform quantum geometry in terms of the Fubini-Study metric is shown to play a key role at low energies strongly interacting lattice models by inducing an emergent interaction-driven dispersion. In particular, this related (de)stabilization both symmetry-broken and topologically ordered states moir\'e systems.
A class of systems is presented in which a particle-antiparticle pair cannot annihilate each other after they have moved along loop and instead form new type composite particle. This occurs so-called non-Hermitian systems: classical metamaterials or ``open'' quantum that are coupled to the rest Universe. In two dimensions, their excitations massless ``particles'' can be created as pairwise. Each particle associated with mathematical structure knot rope. After moving one bringing it near its...