Topological semimetal in a fermionic optical lattice

By K. Sun, W. V. Liu, A. Hemmerich, S. Das Sarma. Nature Physics, 2010

147 citations recorded by the source corpus.

Experimental progress has made it possible to load fermionic atoms into higher orbital bands. Such systems provide a platform for studying quantum states of matter that have no prior analogues in solid-state materials. This theoretical study predicts a semimetallic topological state in these systems, which can be turned into a topological insulating phase. Optical lattices have an important role in advancing our understandingof correlated quantum matter. The recent implementation of orbital degrees of freedom in chequerboard1,2 and hexagonal3 optical lattices opens up a new avenue towards discovering novel quantum states of matter that have no prior analogues in solid-state electronic materials. Here, we predict that an exotic topological semimetal emerges as a parity-protected gapless state in the orbital bands of a two-dimensional fermionic optical lattice. This new quantum state is characterized by a parabolic band-degeneracy point with Berry flux 2π, in sharp contrast to the π flux of Dirac points as in graphene. We show that the appearance of this topological liquid is universal for all lattices with D4 point-group symmetry, as long as orbitals with opposite parities hybridize strongly with each other and the band degeneracy is protected by odd parity. Turning on inter-particle repulsive interactions, the system undergoes a phase transition to a topological insulator whose experimental signature includes chiral gapless domain-wall modes, reminiscent of quantum Hall edge states.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/f55f03ebea825c01348b26faacc25f2fc3bebac7

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In Atomic and Molecular Physics, and Optics

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Citations in the corpus

Weyl and Dirac semimetals in three-dimensional solids (2017, background): “There have also been proposals to realize topological semimetals systems in ultracold atoms in optical lattices (Dubček et al., 2015; Jiang, 2012; Li and Sarma, 2015; Sun et al., 2012).”
Topological quantum matter with ultracold gases in optical lattices (2016, background): “Besides, the orbital degrees of freedom can also be exploited in optical lattices, where Chern bands can emerge through interactions [74, 75].”