Ya-Jie Wu

Majorana modes and s-wave topological superfluids in ultracold fermionic atoms

We present another topological superfluid with s-wave pairing for ultracold fermionic atoms in addition to the chiral topological superfluid proposed by Sato et al (2009 Phys. Rev. Lett. 103 020401), of which edge dislocations host Majorana zero modes that may be utilized as decoherence-free qubits, and quantized vortices trap zero energy modes. The quantum phase fluctuations for topological superfluids and Berezinsky–Kosterlitz–Thouless transition are also discussed.

Topological mid-gap states of px+ipy topological superconductor with vortex square superlattice

Abstract In this paper, the p x + i p y topological superconductor with vortex square superlattice is studied. We calculated the edge spectrum in the presence of vortex superlattice, and found that there exist mid-gap vortex fermion bands induced by the vortex superlattice with nontrivial topological properties, which relate to gapless edge mode and non-zero winding number. Moreover, we proposed a topological anisotropic tight-binding Majorana lattice model to describe the mid-gap states.

Bogoliubov excitations in the Bose-Hubbard extension of a Weyl semimetal

In this paper, a Bose-Hubbard extension of a Weyl semimetal is proposed that can be realized for ultracold atoms using laser assisted tunneling and Feshbach resonance technique in three dimensional optical lattices. The global phase diagram is obtained consisting of a superfluid phase and various Mott insulator phases by using Landau theory. The Bogoliubov excitation modes for the weakly interacting case have nontrivial properties (Weyl nodes, bosonic surface arc, etc.) analogs of those in Weyl semimetals of electronic systems, which are smoothly carried over to that of Bloch bands for the noninteracting case. The properties of the insulating phases for the strongly interacting case are explored by calculating both the quasiparticle and quasihole dispersion relation, which shows two quasiparticle spectra touch at Weyl nodes.

Fermi arcs in tilted Weyl semimetals: Classification, evolution and transport properties

The Weyl semimetal is a new quantum state of a topological semimetal, of which topological surface states —the Fermi arcs— exist. The Fermi arcs of Weyl semimetals are classified into two classes, designated class-1 and class-2. Based on a tight-binding model, the evolution and transport properties of these classes are studied via the tilting strength of the bulk Weyl cones. The (residual) anomalous Hall conductivity of the topological surface states is a physical attribute of class-1 Fermi arcs and hence class-1 Fermi arcs become a nontrivial topological property of either a hybrid or a type-II Weyl semimetal. Therefore, this work provides an intuitive method in learning about the topological properties of Weyl semimetals.

Antiferromagnetic order driven chiral topological spin density waves on the repulsive Haldane-Hubbard model on square lattices.

In this paper, based on mean-field approach and random-phase-approximation, we study the magnetic properties of the repulsive Haldane-Hubbard model on a square lattice. We find antiferromagnetic order driven topological spin density waves beyond Landaus symmetry-breaking paradigm, for which the effective low energy physics is determined by Chern-Simons-Hopf gauge field theories with different K matrices.

Fractionalized flux, Majorana fermions and non-Abelian anyons in topological superfluid on optical lattices

Recently, topological excitations obeying non-Abelian statistics attracted intensive attention because of their exotic statistics and possible applications in topological quantum computation. In this paper, based on a topological s -wave superfluid on a Peierls lattice, we find fractionalized flux and non-Abelian anyons, and then give a realistic proposal to realize the universal topological quantum computation, and especially show how to perform the single-qubit gate–phase-shift gate. Finally, we discuss the experimental realization on optical lattices.

Strongly fluctuating fermionic superfluid in the attractive

Ultracold atoms in optical lattice provides a platform to realize the superfluid (SF) state, a quantum order with paired charge-neutral fermions. In this paper, we studied SF state in the twodimensional attractive Hubbard model with pi-flux on each plaquette. The SF state in the pi-flux lattice model suffers very strong quantum fluctuations and the ground state becomes a possible quantum phase liquid state. In this phase, there exists the Cooper pairing together with a finite energy gap for the atoms, but no long range SF phase coherence exists at zero temperature. In addition, we discussed the properties of the SF vortices.

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In this paper, based on the Haldane model, we study the Chern insulator with superlattice of π-fluxes. We find that there exist mid-gap states induced by the flux-superlattice. In particular, the mid-gap states have nontrivial topological properties, including the nonzero Chern number and the gapless edge states. We derive an effective tight-binding model to describe the topological mid-gap states and then study the mid-gap states by the effective tight-binding model. The results can be straightforwardly generalized to other two-dimensional topological insulators with flux-superlattice.