Chiral and pair superfluidity in triangular ladder produced by state-dependent Kronig-Penney lattice

TL;DR

This paper introduces a novel triangular ladder setup for ultracold atoms with controllable interactions, revealing stable pair superfluidity and chiral superfluid phases through advanced numerical and analytical methods.

Contribution

It presents a new experimental realization of a frustrated triangular ladder with tunable pair hopping and density interactions, and maps the system to an XXZ spin model for phase analysis.

Findings

Stable pair superfluid with power-law pair correlations

Emergence of chiral superfluid due to frustration

Exact phase transition points mapped to XXZ model

Abstract

We propose a concrete realization of a triangular ladder for ultracold atoms, which simultaneously hosts geometric frustration and unusual two-body interactions, and in particular controllable pair hopping and density-induced tunneling. This is done by means of a spin-dependent Kronig-Penney lattice created using a spatially-dependent tripod-type atom-light coupling. We apply density matrix renormalization group (DMRG) calculations to derive the quantum phase diagram. We find that pair tunneling stabilizes a robust pair superfluid, characterized by power-law decay of pair correlations. Additionally, a chiral superfluid arises from frustration induced by competing nearest neighbor (NN) and next-nearest neighbor (NNN) tunnelings. Finally, in the high barrier regime, we map our system onto the XXZ spin model and find the exact phase transition points.