Exotic topological density waves in cold atomic Rydberg-dressed fermions.

Xiaopeng Li,S Das Sarma

doi:10.1038/ncomms8137

Abstract

Versatile controllability of interactions in ultracold atomic and molecular gases has now reached an era where quantum correlations and unconventional many-body phases can be studied with no corresponding analogues in solid-state systems. Recent experiments in Rydberg atomic gases have achieved exquisite control over non-local interactions, allowing novel quantum phases unreachable with the usual local interactions in atomic systems. Here we study Rydberg-dressed atomic fermions in a three-dimensional optical lattice predicting the existence of hitherto unheard-of exotic mixed topological density wave phases. By varying the spatial range of the non-local interaction, we find various chiral density waves with spontaneous time-reversal symmetry breaking, whose quasiparticles form three-dimensional quantum Hall and Weyl semimetal states. Remarkably, certain density waves even exhibit mixed topologies beyond the existing topological classification. Our results suggest gapless fermionic states could exhibit far richer topology than previously expected.

Highlights

Versatile controllability of interactions in ultracold atomic and molecular gases has reached an era where quantum correlations and unconventional many-body phases can be studied with no corresponding analogues in solid-state systems
We demonstrate the existence of such an exotic topological density wave via renormalization group (RG) and self-consistent calculations
Density interactions described by a non-local potential, V(r) 1⁄4 V6/[1 þ (|r|/rc)6], where V6 describes the interaction strength and rc the interaction range determined by the Condon radius in Rydberg dressing[19,21,22,24,25]

Summary

Introduction

Versatile controllability of interactions in ultracold atomic and molecular gases has reached an era where quantum correlations and unconventional many-body phases can be studied with no corresponding analogues in solid-state systems. We study Rydberg-dressed atomic fermions in a three-dimensional optical lattice predicting the existence of hitherto unheard-of exotic mixed topological density wave phases. In the context of ultracold atoms, recent experimental developments have realized quantum control of Rydberg excitations[14,15,16,17,18,19,20], where strong van der Waals interactions lead to long-range interacting quantum systems. This allows novel collective quantum phenomena to be explored qualitatively beyond what are possible with the usual short-range interactions in atomic samples. We propose an experimental scheme to extract the topological properties based on time-of-flight signals

Methods

Results

Conclusion