Two-dimensional Tunable Dirac/Weyl Semimetal in Non-Abelian Gauge Field

Yaowu Guo,Jia-Qiang Zhao,Yan Chen,Jie Lou,Zhi Lin

doi:10.1038/s41598-019-54670-5

Abstract

Three-dimensional(3D) Weyl semimetal(WSM) with linear energy spectra has attracted significant interest. Especially they have been observed experimentally in several solid materials with the breaking of inversion symmetry. Here we predict a new family of particle-hole({mathscr{C}}) invariant 2D WSMs in the non-Abelian gauge field, which can emerge in the low energy bands being close to Fermi energy (dubbed Weyl-I) and the high energy bands being away from Fermi energy (dubbed Weyl-II), only when the time-reversal symmetry({mathscr{T}}) of the 2D Dirac semimetal is broken in the presence of in-plane Zeeman fields. Moreover, a 2D Dirac node can split into a pair of Weyl nodes showing the same Berry phase, and the 2D WSM, being protected by {mathscr{T}} symmetry, exhibits four Weyl-I nodes, whose energies are invariant with the variation of the magnetic field. The corresponding Fermi velocity and Berry connection have been calculated. Based on the 2D WSMs, we also examine inhomogeneous pairings of attractive Fermi gases and find a new kind of the LO states with the beat frequency. This 2D WSM provides a realistic and promising platform for exploring and manipulating exotic Weyl physics, which may increase the experimental feasibility in the context of ultracold atoms.

Highlights

We theoretically propose and study the 2D WSM with cold atoms in a square optical lattice subjected to the non-Abelian gauge field, and successfully identify the Weyl points and their evolutions by the single-particle spectra and the Bloch Zener Oscillation technique under different hx
The Fermi velocities and Berry connections of the 2D WSM are manifestly uncovered with the change of the magnetic field
Based on the particular structure of the Fermi surface in the 2D WSM, we examine the superfluidity of attractive Fermi gases, and the FFLO states with different beats are revealed, which significantly enriches and deepens our awareness of the novel and inhomogeneous superfluid states

Summary

Gauge Field

Three-dimensional(3D) Weyl semimetal(WSM) with linear energy spectra has attracted significant interest. Based on the 2D WSMs, we examine inhomogeneous pairings of attractive Fermi gases and find a new kind of the LO states with the beat frequency This 2D WSM provides a realistic and promising platform for exploring and manipulating exotic Weyl physics, which may increase the experimental feasibility in the context of ultracold atoms. The size of the positive and negative energy of these Weyl-II points is consistent with the size of the in-plane Zeeman field strength, and the variation of the Zeeman field only modulates their energy positions Based on this WSM, a novel FFLO pairing of attractive Fermi gases with the beat phenomenon can be formed on pairs of the Fermi surfaces of the system

Model Hamiltonian

The Emergence of Weyl Points

Using the vector

Detection of the WSM using the Bloch Zener Oscillation

Summary

Additional information