Planckian Dissipation in Metals

TL;DR

This paper reviews the concept of Planckian dissipation timescales in metals, clarifying different physical timescales and exploring the potential fundamental bounds on dissipation from quasiparticle and many-body perspectives.

Contribution

It provides a comprehensive, pedagogical analysis of Planckian timescales in metals, clarifying previous confusions and discussing bounds from multiple theoretical viewpoints.

Findings

Planckian timescales appear in both conventional and unconventional metals.

Different characteristic timescales can coincide or differ depending on conditions.

The paper discusses potential fundamental bounds on dissipation based on quasiparticle and many-body theories.

Abstract

We review the appearance of the Planckian time $\tau_\text{Pl} = \hbar/(k_B T)$ in both conventional and unconventional metals. We give a pedagogical discussion of the various different timescales (quasiparticle, transport, many-body) that characterize metals, emphasizing conditions under which these times are the same or different. Throughout, we have attempted to clear up aspects of the problem that had been confusing us, in the hope that this helps the reader as well. We discuss the possibility of a Planckian bound on dissipation from both a quasiparticle and a many-body perspective. Planckian quasiparticles can arise naturally from a combination of inelastic scattering and mass renormalization. Many-body dynamics, on the other hand, is constrained by the basic time- and length- scales of local thermalization.