A5085385194- Topological Materials and Phenomena
- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Iron-based superconductors research
- Quantum many-body systems
- Graphene research and applications
- Quantum, superfluid, helium dynamics
- Quantum Mechanics and Non-Hermitian Physics
- Cold Atom Physics and Bose-Einstein Condensates
- Rare-earth and actinide compounds
- Electronic and Structural Properties of Oxides
- Magnetic and transport properties of perovskites and related materials
- Theoretical and Computational Physics
- 2D Materials and Applications
- Mechanical and Optical Resonators
- Nonlinear Photonic Systems
- Algebraic structures and combinatorial models
- Quantum chaos and dynamical systems
- Atomic and Subatomic Physics Research
- Surface and Thin Film Phenomena
- Organic and Molecular Conductors Research
- Black Holes and Theoretical Physics
- Corporate Taxation and Avoidance
- Superconductivity in MgB2 and Alloys
University of Würzburg
2016-2025
Complexity and Topology in Quantum Matter
2023-2025
Instituto de Física Teórica
2024
Indian Institute of Technology Madras
2021-2024
Institute of Physics
2018
Chinese Academy of Sciences
2018
Stanford University
2012-2016
École Polytechnique Fédérale de Lausanne
2013
École Polytechnique
2013
Princeton University
2010-2012
Quantum spin Hall (QSH) materials promise revolutionary device applications based on dissipationless propagation of currents. They are two-dimensional (2D) representatives the family topological insulators, which exhibit conduction channels at their edges inherently protected against scattering. Initially predicted for graphene, and eventually realized in HgTe quantum wells, QSH systems so far, decisive bottleneck preventing is small bulk energy gap less than 30 meV, requiring cryogenic...
Combining thermodynamic measurements with theoretical calculations we demonstrate that the iridates ${A}_{2}{\mathrm{IrO}}_{3}$ ($A=\mathrm{Na}$, Li) are magnetically ordered Mott insulators where magnetism of effective spin-orbital $S=1/2$ moments can be captured by a Heisenberg-Kitaev (HK) model interactions beyond nearest-neighbor exchange. Experimentally, observe an increase Curie-Weiss temperature from $\ensuremath{\theta}\ensuremath{\approx}\ensuremath{-}125\text{ }\text{ }\mathrm{K}$...
Non-Hermitian systems can exhibit a counterintuitive phenomenon where single local boundary or disorder modifies the entire spectrum, no matter how large system is. In such cases, all bulk modes become localized ``skin'' modes, and usual topological invariants longer correctly predict modes. Generalizing Laughlin's gauge argument to complex fluxes, authors derive geometrical approach for exact determination of skin-mode spectrum. They also devise new criterion non-Hermitian particle-hole...
A topological light funnel Because most physical systems cannot be totally isolated from their environment, some degree of dissipation or loss is expected. The successful operation such generally relies on mitigating for that loss. Mathematically, external interactions are described as non-Hermitian. Recent work has shown controlling the gain and in these gives rise to a wide variety exotic phenomena not expected Hermitian counterparts. Using time-dependent photonic lattice which properties...
Invented by Alessandro Volta and F\'elix Savary in the early 19th century, circuits consisting of resistor, inductor capacitor (RLC) components are omnipresent modern technology. The behavior an RLC circuit is governed its Laplacian, which analogous to Hamiltonian describing energetics a physical system. We show that topological semimetal band structures can be realized as admittance bands periodic circuit, where we employ grounding adjust spectral position similar chemical potential...
We investigate the competing Fermi surface instabilities in kagome tight-binding model. Specifically, we consider on-site and short-range Hubbard interactions vicinity of van Hove filling dispersive bands where fermiology promotes joint effect enlarged density states nesting. The sublattice interference mechanism devised by Kiesel Thomale [Phys. Rev. B 86, 121105 (2012)] allows us to explain intricate interplay between ferromagnetic fluctuations other ordering tendencies. On basis functional...
The band structure of graphene exhibits van Hove singularities (VHS) at doping x=+- 1/8 away from the Dirac point. Near VHS, interactions effects, enhanced due to large density states, can give rise various many-body phases experimentally accessible temperatures. We study competition between different instabilities in using functional renormalization group (FRG). predict a rich phase diagram, which, depending on long range hopping as well screening strength and absolute scale Coulomb...
We propose an electric circuit array with topologically protected unidirectional voltage modes at its boundary. Instead of external bias fields or Floquet engineering, we employ negative impedance converters current inversion (INICs) to accomplish a nonreciprocal, time-reversal symmetry-broken electronic network call topolectrical Chern (TCC). The TCC features admittance bulk gap fully tunable via the resistors used in INICs, along chiral boundary mode reminiscent Berry flux monopole present...
We investigate the spin-$\frac{1}{2}$ Heisenberg model on triangular lattice in presence of nearest-neighbor $J_1$ and next-nearest-neighbor $J_2$ antiferromagnetic couplings. Motivated by recent findings from density-matrix renormalization group (DMRG) claiming existence a gapped spin liquid with signatures spontaneously broken point symmetry [Zhu White, Phys. Rev. B 92, 041105 (2015); Hu, Gong, Zhu, Sheng, 140403 (2015)], we employ variational Monte Carlo (VMC) approach to analyze an...
We study the electronic phases of kagome Hubbard model (KHM) in weak coupling limit around van Hove filling. Through an analytic renormalization group analysis, we find that there exists a sublattice interference mechanism where structure affects character Fermi surface instabilities. It leads to major suppression Tc for d+id superconductivity KHM and causes anomalous increase upon addition longer-range interactions. conjecture conventional liquid instabilities makes prototype candidate...
Motivated by the recent observation of superconductivity in strontium doped NdNiO$_2$, we study superconducting instabilities this system from various vantage points. Starting with first-principles calculations, construct two distinct tight-binding models, a simpler single-orbital as well three-orbital model, both which capture key low energy degrees freedom to varying degree accuracy. We models using random phase approximation (RPA). then analyze problem at stronger coupling, and dominant...
The recent discovery of AV_{3}Sb_{5} (A=K,Rb,Cs) has uncovered an intriguing arena for exotic Fermi surface instabilities in a kagome metal. Among them, superconductivity is found the vicinity multiple van Hove singularities, exhibiting indications unconventional pairing. We show that sublattice interference mechanism central to understanding formation Starting from appropriately chosen minimal tight-binding model with singularities close level AV_{3}Sb_{5}, we provide random phase...
Abstract The recently discovered layered kagome metals AV 3 Sb 5 (A = K, Rb, Cs) exhibit diverse correlated phenomena, which are intertwined with a topological electronic structure multiple van Hove singularities (VHSs) in the vicinity of Fermi level. As VHSs their large density states enhance correlation effects, it is crucial importance to determine nature and properties. Here, we combine polarization-dependent angle-resolved photoemission spectroscopy functional theory directly reveal...
We employ electric circuit networks to study topological states of matter in non-Hermitian systems enriched by parity-time symmetry $\mathcal{P}\mathcal{T}$ and chiral anti-$\mathcal{P}\mathcal{T}$ ($\mathcal{A}\mathcal{P}\mathcal{T}$). The structure manifests itself the complex admittance bands which yields excellent measurability signal noise ratio. analyze impact $\mathcal{P}\mathcal{T}$-symmetric gain loss on localized edge defect a Su-Schrieffer-Heeger (SSH) circuit. realize all three...
Abstract Topological photonics seeks to control the behaviour of light through design protected topological modes in photonic structures. While this approach originated from studying electrons solid-state materials, it has since blossomed into a field that is at very forefront search for new types matter. This can have real implications future technologies by harnessing robustness applications devices. roadmap surveys some main emerging areas research within photonics, with special attention...
Hyperbolic lattices are a revolutionary platform for tabletop simulations of holography and quantum physics in curved space facilitate efficient error correcting codes. Their underlying geometry is non-Euclidean, the absence Bloch's theorem precludes straightforward application often indispensable energy band theory to study model Hamiltonians on hyperbolic lattices. Motivated by recent insights into theory, we initiate crystallography We show that many feature hidden crystal structure...
The Laplace operator encodes the behavior of physical systems at vastly different scales, describing heat flow, fluids, as well electric, gravitational, and quantum fields. A key input for equation is curvature space. Here we discuss experimentally demonstrate that spectral ordering Laplacian eigenstates hyperbolic (negatively curved) flat two-dimensional spaces has a universally structure. We use lattice regularization space in an electric-circuit network to measure 'hyperbolic drum',...
Abstract Curved spaces play a fundamental role in many areas of modern physics, from cosmological length scales to subatomic structures related quantum information and gravity. In tabletop experiments, negatively curved can be simulated with hyperbolic lattices. Here we introduce experimentally realize matter as paradigm for topological states through topolectrical circuit networks relying on complex-phase element. The experiment is based band theory that confirm here an unprecedented...