Emergent pseudospin-1 Maxwell fermions with a threefold degeneracy in optical lattices

TL;DR

This paper introduces models for realizing emergent spin-1 Maxwell fermions with threefold degeneracy in optical lattices, revealing rich topological phenomena and proposing experimental detection methods.

Contribution

It constructs novel tight-binding models for spin-1 Maxwell fermions in optical lattices, expanding the types of relativistic excitations studied in condensed matter physics.

Findings

Maxwell points exhibit quantized Berry phases and quantum Hall effects.

Maxwell points in 3D have monopole charges of 2 and Fermi arcs.

Topological phase transitions occur through Maxwell point merging.

Abstract

The discovery of relativistic spin-1/2 fermions such as Dirac and Weyl fermions in condensed-matter or artificial systems opens a new era in modern physics. An interesting but rarely explored question is whether other relativistic spinal excitations could be realized with artificial systems. Here, we construct twoand three-dimensional tight-binding models realizable with cold fermionic atoms in optical lattices, where the low energy excitations are effectively described by the spin-1 Maxwell equations in the Hamiltonian form. These relativistic (linear dispersion) excitations with unconventional integer pseudospin, beyond the Dirac-Weyl-Majorana fermions, are an exotic kind of fermions named asMaxwell fermions.We demonstrate that the systems have rich topological features. For instance, the threefold degenerate points called Maxwell points may have quantized Berry phases and anomalous quantum Hall effects with spin-momentum locking may appear in topological Maxwell insulators in the two-dimensional lattices. In three dimensions,Maxwell points may have nontrivial monopole charges of \pm2 with two Fermi arcs connecting them, and the merging of the Maxwell points leads to topological phase transitions. Finally, we propose realistic schemes for realizing the model Hamiltonians and detecting the topological properties of the emergent Maxwell quasiparticles in optical lattices.