197485150
Searching for New Topological Types of Majorana Fermions from Boundary-bulk Correspondence of Topological Insulators/Superconductors
Majorana fermions (MFs) are particles that are their own anti-particles and may satisfy non-Abelian statistics. For the past ten years, a kind of MFs have been theoretically predicted in one-dimensional superconducting models without the time-reversal symmetry (TRS), which has recently intrigued a huge experimental interest to search for this type of exotic particles. Here we report our theoretical discoveries, including (i) a general and quantitative relation between topological stabilities of Fermi surfaces (FSs) and topological insulators(TIs)/superconductors(TSCs) is rigorously established; (ii) based on (i), we find four topologically distinct types of MFs in fermionic systems that have at least the particle-hole symmetry (PHS); (iii) apart from the existing one type, three new types of topologically nontrivial gapless edge-modes (MFs) are revealed for the first time in one dimensional finite systems with both TP and (iv) all kinds of candidate models that potentially have MFs are presented, opening a wider door for searching MFs experimentally.
56250567
Macroscopic Klein tunneling in spin-orbit-coupled Bose-Einstein condensates
We propose an experimental scheme to detect macroscopic Klein tunneling with spin-orbit coupled Bose-Einstein condensates (BECs). We show that a nonlinear Dirac equation with tunable parameters can be realized with such BECs. %in a simple configuration to generate the artificial spin-orbit coupling. Through numerical calculations, we demonstrate that macroscopic Klein tunneling can be clearly detected under realistic conditions. Macroscopic quantum coherence in such relativistic tunneling is clarified and a BEC with a negative energy is shown to be able to transmit transparently through a wide Gaussian potential barrier.
118521941
Relativistic quantum effects of Dirac particles simulated by ultracold atoms
Quantum simulation is a powerful tool to study a variety of problems in physics, ranging from high-energy physics to condensed-matter physics. In this article, we review the recent theoretical and experimental progress in quantum simulation of Dirac equation with tunable parameters by using ultracold neutral atoms trapped in optical lattices or subject to light-induced synthetic gauge fields. The effective theories for the quasiparticles become relativistic under certain conditions in these systems, making them ideal platforms for studying the exotic relativistic effects. We focus on the realization of one, two, and three dimensional Dirac equations as well as the detection of some relativistic effects, including particularly the well-known Zitterbewegung effect and Klein tunneling. The realization of quantum anomalous Hall effects is also briefly discussed.
119293149
Particle-number fractionalization of a one-dimensional atomic Fermi gas with synthetic spin-orbit coupling
We propose an experimental scheme to simulate the fractionalization of the particle number by using a one-dimensionalspin-orbit-coupledultracoldfermionicgas.Thedesiredspin-orbitcoupling,akinklikepotential, andaconjugation-symmetry-breakingmasstermareproperlyconstructedbylaser-atominteractions,leadingtoan effectivelow-energyrelativisticDiracHamiltonianwithatopologicallynontrivialbackgroundfield.Thedesigned system supports a localized soliton excitation with a fractional particle number that is generally irrational and experimentally tunable, providing a direct realization of the celebrated generalized Su-Schrieffer-Heeger model. In addition, we elaborate on how to detect the induced soliton mode with the fractional particle number in the system.
34602223
Probing non-abelian statistics of Majorana fermions in ultracold atomic superfluid.
We propose an experiment to directly probe the non-abelian statistics of Majorana fermions by braiding them in an s-wave superfluid of ultracold atoms. We show that different orders of braiding operations give orthogonal output states that can be distinguished through Raman spectroscopy. Realization of Majorana states in an s-wave superfluid requires strong spin-orbital coupling and a controllable Zeeman field in the perpendicular direction. We present a simple laser configuration to generate the artificial spin-orbital coupling and the required Zeeman field in the dark-state subspace.
126306148
Quantum simulation of DIII class topological superconductors using superconducting quantum circuits
Yong Hu, Y. X. Zhao, Zheng-Yuan Xue, and Z. D. Wang Department of Physics and Center of Theoretical and Computational Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China School of Physics, Huazhong University of Science and Technology, Wuhan, 430074, China and Laboratory of Quantum Engineering and Quantum Materials, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006, China
119278662
Symmetry, Defects, and Gauging of Topological Phases
We examine the interplay of symmetry and topological order in $2+1$ dimensional topological phases of matter. We present a definition of the topological symmetry group, which characterizes the symmetry of the emergent topological quantum numbers of a topological phase $\mathcal{C}$, and we describe its relation with the microscopic symmetry of the underlying physical system. We derive a general framework to classify symmetry fractionalization in topological phases, including phases that are non-Abelian and symmetries that permute the quasiparticle types and/or are anti-unitary. We develop a theory of extrinsic defects (fluxes) associated with elements of the symmetry group, which provides a general classification of symmetry-enriched topological phases derived from a topological phase of matter $\mathcal{C}$ with symmetry group $G$. The algebraic theory of the defects, known as a $G$-crossed braided tensor category $\mathcal{C}_{G}^{\times}$, allows one to compute many properties, such as the number of topologically distinct types of defects associated with each group element, their fusion rules, quantum dimensions, zero modes, braiding exchange transformations, a generalized Verlinde formula for the defects, and modular transformations of the $G$-crossed extensions of topological phases. We also examine the promotion of the global symmetry to a local gauge invariance, wherein the extrinsic $G$-defects are turned into deconfined quasiparticle excitations, which results in a different topological phase $\mathcal{C}/G$. A number of instructive and/or physically relevant examples are studied in detail.
119491970
Analysis of the vertices rho NN, rho Sigma Sigma and rho Xi Xi with light-cone QCD sum rules
In this article, we calculate the strong coupling constants of the {rho}NN, {rho}{sigma}{sigma}, and {rho}{xi}{xi} in the framework of the light-cone QCD sum rules approach. The strong coupling constants of the meson-baryon-baryon are the fundamental parameters in the one-boson exchange model which describes the baryon-baryon interactions successfully. The numerical values are in agreement with the existing calculations in part. The electric and magnetic F/(F+D) ratios deviate from the prediction of the vector meson dominance theory; the SU(3) symmetry breaking effects are very large.
118588275
Analysis of the $X(1835)$ as a baryonium state with Bethe-Salpeter equation
In this article, we take the X(1835) as a pseudoscalar baryonium state, and calculate the mass spectrum of the baryon-antibaryon bound states pp̄, ΣΣ̄, ΞΞ̄, and ΛΛ̄ in the framework of the Bethe-Salpeter equation with a phenomenological potential. The numerical results indicate the pp̄, ΣΣ̄ and ΞΞ̄ bound states maybe exist, and the X(1835) can be tentatively identified as the pp̄ bound state. PACS number: 12.39.Ki, 12.39.Pn
120394115
Manipulation of Majorana fermions by point-like gate voltage in the Vortex state of a topological superconductor
A vortex in a topological superconductor induces two Majorana fermions (MFs), one in the core and the other at the sample edge. Here we demonstrate that edge MFs can be transported and braided by turning gate voltages on and off at the point-like constriction junctions between samples. The controllable high mobility of edge MFs is due to the topological property, namely an edge MF appears when the sample perimeter includes odd vorticity, and disappears for even vorticity. As shown explicitly by solving the time-dependent Bogoliubov-de Gennes equation, disturbance to the quantum coherence of MFs during braiding is negligibly small in this scheme due to the point-like application of the gate voltage. The present work bridges for the first time the fundamental topological features of edge MFs and their adiabatic dynamics which is important for performing topological quantum computation.
21495965
Pressure-induced cubic to monoclinic phase transformation in erbium sesquioxide Er(2)O(3).
Cubic Er(2)O(3) was compressed in a symmetric diamond anvil cell at room temperature and studied in situ using energy-dispersive X-ray diffraction. A transition to a monoclinic phase began at 9.9 GPa and was complete at 16.3 GPa and was accompanied by a approximately 9% volume decrease. The monoclinic phase was stable up to at least 30 GPa and could be quenched to ambient conditions. The normalized lattice parameter compression data for both phases were fit to linear equations, and the volume compression data were fit to third-order Birch-Murnaghan equations of state. The zero-pressure isothermal bulk moduli (B(0)) and the first-pressure derivatives (B(0)') for the cubic and monoclinic phases were 200(6) GPa and 8.4 and also 202(2) GPa and 1.0, respectively. Ab initio density functional theory calculations were performed to determine optimized lattice parameters and atom positions for the cubic, monoclinic, and hexagonal phases of Er(2)O(3). The calculated X-ray spectra and predicted transition pressure are in good qualitative agreement with the experimental results.