A5070327120- Topological Materials and Phenomena
- Graphene research and applications
- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Advanced Condensed Matter Physics
- 2D Materials and Applications
- Iron-based superconductors research
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum many-body systems
- Rare-earth and actinide compounds
- Atomic and Subatomic Physics Research
- Quantum, superfluid, helium dynamics
- Electronic and Structural Properties of Oxides
- Surface and Thin Film Phenomena
- Magnetic properties of thin films
- Organic and Molecular Conductors Research
- Theoretical and Computational Physics
- Molecular Junctions and Nanostructures
- Machine Learning in Materials Science
- Magnetic Field Sensors Techniques
- Superconductivity in MgB2 and Alloys
- Quantum optics and atomic interactions
- Quantum Computing Algorithms and Architecture
- Magnetic Properties and Applications
- Advanced Memory and Neural Computing
Hong Kong University of Science and Technology
2016-2025
University of Hong Kong
2016-2025
Massachusetts Institute of Technology
2009-2010
Brown University
2006-2008
University of California, Berkeley
2003
We describe experimental signatures of Majorana fermion edge states, which form at the interface between a superconductor and surface topological insulator. If lead couples to fermions through electron tunneling, induce resonant Andreev reflections from grounded superconductor. The linear tunneling conductance is 0 (2e(2)/h) if there an even (odd) number vortices in Similar resonance occurs for into zero mode vortex core. also study current noise two-lead device.
The Zeeman effect, which is usually considered to be detrimental superconductivity, can surprisingly protect the superconducting states created by gating a layered transition metal dichalcogenide. This effective field, originated from intrinsic spin orbit coupling induced breaking in-plane inversion symmetry, reach nearly hundred Tesla in magnitude. It strongly pins orientation of electrons out-of-plane directions and protects superconductivity being destroyed an external magnetic field. In...
One of the simplest proposed experimental probes a Majorana bound-state is quantized (2e^2/h) value zero-bias tunneling conductance. When temperature somewhat larger than intrinsic width peak, conductance no longer quantized, but peak can remain. Such non-quantized has been recently reported for semiconducting nanowires with proximity induced superconductivity. In this paper we analyze relation to presence end-states, by simulating multi-band wires realistic amounts disorder. We show that...
Significance In solids with an odd number of electrons per unit cell, band theory requires that they are metals, but strong interaction can turn them into insulators, called Mott insulators. this case, the form local moments that, in turn, antiferromagnetic ground state. 1973, P. W. Anderson proposed certain cases, quantum fluctuations may prevent magnetic order and result a paramagnetic state spin liquid. After many years searching, few examples have been discovered past several years. We...
A Majorana zero bound mode exists in the vortex core of a chiral $p+ip$ superconductor or superfluid, which can be driven from an $s$-wave pairing state by two-dimensional spin-orbit coupling. We propose here novel scheme based on realistic cold atom platforms to generate interactions blue-detuned square optical lattice, and predict both quantum anomalous Hall effect topological superfluid phase experimentally accessible parameter regimes. This work may open new direction with experimental...
The coexistence of gate-tunable superconducting, magnetic and topological orders in magic-angle twisted bilayer graphene provides opportunities for the creation hybrid Josephson junctions. Here we report fabrication gate-defined symmetry-broken junctions graphene, where weak link is gate-tuned close to correlated insulator state with a moiré filling factor υ = -2. We observe phase-shifted asymmetric Fraunhofer pattern pronounced hysteresis. Our theoretical calculations junction link-with...
Moiré heterobilayer transition metal dichalcogenides (TMDs) emerge as an ideal system for simulating the single-band Hubbard model and interesting correlated phases have been observed in these systems. Nevertheless, moiré bands TMDs were believed to be topologically trivial. Recently, it was reported that both a quantum valley Hall insulating state at filling ν=2 (two holes per unit cell) valley-polarized anomalous ν=1 AB stacked MoTe_{2}/WSe_{2} heterobilayers. However, how nontrivial...
In recent years, it has been shown that Berry curvature monopoles and dipoles play essential roles in the anomalous Hall nonlinear effects, respectively. this work, we demonstrate multipoles (the higher moments of curvatures at Fermi energy) can induce higher-order (NLAH) effects. Specifically, an AC voltage perpendicular to current direction emerges, where frequency is integer multiple applied current. Importantly, by analyzing symmetry properties all 3D 2D magnetic point groups, note...
Recent experimental studies unveiled highly unconventional phenomena in the superconducting twisted bilayer graphene (TBG) with ultraflat bands, which cannot be described by conventional BCS theory. For example, given small Fermi velocity of flat coherence length predicted theory is more than 20 times shorter measured values. A new needed to understand many properties flat-band superconductors. In this Letter, we establish a Ginzburg-Landau (GL) from microscopic Hamiltonian. The GL shows how...
The coherence length ξ is the fundamental scale of superconductors which governs sizes Cooper pairs, vortices, Andreev bound states, and more. In BCS theory, ξBCS = ℏvF/Δ, where vF Fermi velocity Δ pairing gap. It clear that increasing will shorten ξBCS. this work, we show quantum metric, real part geometric tensor, gives rise to an anomalous contribution length. Specifically, $$\xi =\sqrt{{\xi }_{{{{\rm{BCS}}}}}^{2}+{\ell }_{{{{\rm{qm}}}}}^{2}}$$ for a superconductor ℓqm metric...
Due to its noncentrosymmetric lattice structure, a monolayer of transition metal dichalcogenides (TMD) possesses very special type spin-orbit coupling (SOC) called Ising SOC. Unlike Rashba SOC, SOC pins electron spins the out-of-plane rather than in-plane direction. In TMD materials, is quite strong and substantially enhances upper critical field their superconducting state. Despite this, authors show here that can in fact lead spin-triplet Cooper pairing with electrons pointing Such induces...
Molybdenum disulphide (MoS2) has attracted much interest in recent years due to its potential applications a new generation of electronic devices. Recently, it was shown that thin films MoS2 can become superconducting with highest Tc 10 K when the material is heavily gated conducting regime. In this work, using group theoretical approach, we determine possible pairing symmetries MoS2. Depending on electron-electron interactions and Rashba spin-orbit coupling, support an exotic spin-singlet...
Motivated by recent experimental findings of correlating insulator and superconductor behavior in twisted bilayer graphene, the authors study a cluster charge interaction model on honeycomb lattice. The is defined dual lattice to mimic centers forming triangular found experiments. Based unbiased sign-problem-free quantum Monte Carlo simulations, determine phase diagram for this model. It features fermionic critical point with chiral XY universality Kekul\'e valence bond solid at intermediate...
In this work, we find that Majorana fermions induce selective equal spin Andreev reflections (SESARs), in which incoming electrons with certain polarization the lead are reflected as counter propagating holes same spin. The direction of channel is selected by fermions. Moreover, opposite always unchanged As a result, charge current spin-polarized. Therefore, topological superconductor supports can be used novel device to create fully spin-polarized currents paramagnetic leads. We point out...
In this work, we show that a quasi-one-dimensional ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$-wave superconductor with Rashba spin-orbit coupling is DIII class, time-reversal invariant, topological (TS), which supports Majorana Kramers Doublet (MKD) at each end of the TS. A MKD pair states (MESs) protected by symmetry (TRS). An external magnetic field breaks TRS and drives system from to D class in case single MES appears We induces resonant Andreev reflection zero-bias conductance peak...
Under certain conditions, a fermion in superconductor can separate space into two parts known as Majorana zero modes, which are immune to decoherence from local noise sources and attractive building blocks for quantum computers. Promising experimental progress has been made demonstrate modes materials with strong spin-orbit coupling proximity coupled superconductors. Here we report signatures of material platform utilizing the surface states gold. Using scanning tunneling microscope probe...
Recently, quantum anomalous Hall effect with spontaneous ferromagnetism was observed in twisted bilayer graphenes (TBG) near 3/4 filling. Importantly, it that an extremely small current can switch the direction of magnetization. This offers prospect realizing low energy dissipation magnetic memories. However, mechanism current-driven magnetization switching is poorly understood as charge currents are generally believed to be non-magnetic. In this work, we demonstrate TBG, twisting and...
1T-TaS_{2} is a cluster Mott insulator on the triangular lattice with 13 Ta atoms forming star of David as unit cell. We derive two-dimensional XXZ spin-1/2 model four-spin ring exchange term to describe effective low energy physics monolayer 1T-TaS_{2}, where degrees freedom arises from Kramers degenerate spin-orbital states each David. A large scale density matrix renormalization group simulation further performed this and we find gapless spin liquid phase spinon Fermi surface at moderate...
The study of non-Abelian Majorana zero modes advances our understanding the fundamental physics in quantum matter, and pushes potential applications such exotic states to topological computation. It has been shown that two-dimensional (2D) 1D chiral superconductors, isolated fermions obey statistics. However, a $Z_2$ time-reversal invariant (TRI) superconductor come pairs due Kramers' theorem. Therefore, braiding operations TRI superconductors always exchange two Majoranas. In this work, we...
Abstract Electrons hopping in two-dimensional honeycomb lattices possess a valley degree of freedom addition to charge and spin. In the absence inversion symmetry, these systems were predicted exhibit opposite Hall effects for electrons from different valleys. Such have been achieved only by extrinsic means, such as substrate coupling, dual gating, light illuminating. Here we report first observation intrinsic transport without any symmetry breaking non-centrosymmetric monolayer trilayer MoS...