Response functions and superfluid density in a weakly interacting Bose gas with non-quadratic dispersion

TL;DR

This paper investigates how non-quadratic dispersion in a weakly interacting Bose gas affects response functions, superfluid density, and the Berezhinski-Kosterlitz-Thouless transition, with implications for quasiparticle Bose condensation experiments.

Contribution

It introduces modifications to response functions and sum rules due to non-quadratic dispersion, analyzing their impact on superfluid properties and phase transitions.

Findings

Non-quadratic dispersion alters the particle current definition.

Modified sum rules affect the current-current response function.

Implications for Bose condensation of quasiparticles in semiconductors.

Abstract

Motivated by the experimental search for Bose condensation of quasiparticles in semiconductors, the response functions of a weakly interacting Bose gas, with isotropic but non-quadratic dispersion, are considered. Non-quadratic dispersion modifies the definition of particle current, and leads to modified sum rules for the current-current response function. The effect of these modifications on the Berezhinski-Kosterlitz-Thouless transition is discussed.