Universal linear in temperature resistivity from black hole superradiance

TL;DR

This paper demonstrates that at a holographic BKT critical point, coupling an unstable operator to the current yields a universal linear temperature resistivity, providing insight into unconventional material behaviors.

Contribution

It introduces a holographic mechanism where irrelevant couplings at a BKT critical point produce universal linear resistivity and broad optical conductivity tails.

Findings

Universal linear in temperature resistivity at BKT critical point

Broad power law tails in optical conductivity

Partial realization using Einstein-Maxwell-pseudoscalar theory

Abstract

Observations across many families of unconventional materials motivative the search for robust mechanisms producing linear in temperature d.c. resistivity. BKT quantum phase transitions are commonplace in holographic descriptions of finite density matter, separating critical and ordered phases. We show that at a holographic BKT critical point, if the unstable operator is coupled to the current via irrelevant operators, then a linear contribution to the resistivity is universally obtained. We also obtain broad power law tails in the optical conductivity, that shift spectral weight from the Drude peak as well as interband energy scales. We give a partial realization of this scenario using an Einstein-Maxwell-pseudoscalar bulk theory. The instability is a vectorial mode at nonzero wavevector, which is communicated to the homogeneous current via irrelevant coupling to an ionic lattice.