Comment on "Negative Differential Conductivity in an Interacting Quantum Gas."

TL;DR

This paper explains negative differential conductivity in a Bose-Einstein condensate through macroscopic self-trapping, showing that collisional decoherence only quantitatively modifies the phenomenon rather than causing it.

Contribution

It provides a theoretical analysis demonstrating that NDC arises from unitary dynamics via macroscopic self-trapping, challenging the previous attribution to nonlinear tunneling and decoherence.

Findings

NDC can be explained by macroscopic self-trapping in unitary dynamics.

Collisional decoherence modifies but does not cause NDC.

Theoretical results align with experimental observations.

Abstract

Labouvie \etal (\prl {\bf 115}, 050601, (20015)) recently demonstrated negative differential conductivity (NDC) in a multi-well Bose-Einstein condensate. They stated "we demonstrate that NDC originates from a nonlinear, atom number dependent tunneling coupling in combination with fast collisional decoherence." We show theoretically how the essential feature of NDC, a reduction in atomic current caused by an increase in chemical potential, is present in unitary dynamics through the well-known mechanism of macroscopic self-trapping (MST), and that the collisional decoherence merely serves as a quantitative modification of this.