Asymmetry and nonlinearity of current-bias characteristics in superfluid-normal state junctions of weakly-interacting Bose gases

TL;DR

This paper investigates the current-bias behavior in superfluid-normal state junctions of weakly-interacting Bose gases, revealing asymmetries and nonlinearities due to condensate tunneling and bosonic Andreev reflection, especially under chemical potential bias.

Contribution

It introduces the unique nonlinear current-bias characteristics caused by bosonic processes absent in fermionic systems, highlighting the role of condensate tunneling and Andreev reflection.

Findings

Current-bias characteristics are asymmetric under chemical potential bias.

Bosonic Andreev reflection leads to intrinsic nonlinearity in transport.

Transport driven by temperature bias obeys Ohm's law and is dominated by other processes.

Abstract

We uncover current-bias characteristics of superfluid-normal state junctions with weakly-interacting Bose gases. It is shown that in the presence of a chemical potential bias the characteristics can strongly be asymmetric for origin. The salient feature that is absent in the fermionic counterpart arises from a tunneling process associated with a condensate and a bosonic Andreev reflection process. It turns out that such processes are intrinsically nonlinear and therefore do not obey Ohm's law even at a low bias. In addition, the remaining processes are found to obey Ohm's law and become dominant for transport driven by a temperature bias.