Transverse Quantum Fluids

TL;DR

This paper introduces Transverse Quantum Fluids (TQF), a class of quantum systems with unique superfluid properties, focusing on an incoherent TQF formed by coupled Luttinger liquids that challenges traditional quasiparticle-based superfluidity.

Contribution

The paper defines TQF, analyzes an incoherent TQF state in coupled Luttinger liquids, and highlights its topological protection and lack of low-energy quasiparticles, expanding understanding of superfluidity.

Findings

Incoherent TQF exhibits long-range order without low-energy quasiparticles.

Topological protection prevents quantum phase slips in the incoherent TQF.

The study suggests new experimental directions in condensed matter and cold atomic systems.

Abstract

Motivated by remarkable properties of superfluid edge dislocations in solid Helium-4, we discuss a broad class of quantum systems -- boundaries in phase separated lattice states, magnetic domain walls, and ensembles of Luttinger liquids -- that can be classified as Transverse Quantum Fluids (TQF). After introducing the general idea of TQF, we focus on a coupled array of Luttinger liquids forming an incoherent TQF. This state is a long-range ordered quasi-one-dimensional superfluid, topologically protected against quantum phase slips by tight-binding of instanton dipoles, that has no coherent quasi-particle excitations at low energies. Incoherent TQF is a striking example of the irrelevance of the Landau quasiparticle criterion for superfluidity in systems that lack Galilean invariance. We detail its phenomenology, to motivate a number of experimental studies in condensed matter and cold atomic systems.