Observing the origin of superconductivity in quantum critical metals

TL;DR

This paper proposes that the energy scaling differences in unconventional superconductors are reflected in the dynamical pair susceptibility, which can be experimentally measured to directly investigate the origins of quantum critical superconductivity.

Contribution

It introduces the concept of a 'pairing telescope' using dynamical pair susceptibility measurements to directly explore the mechanisms behind quantum critical superconductivity.

Findings

Energy scaling differences are encoded in pair susceptibility.

Proposes measuring pair susceptibility via the second order Josephson effect.

Introduces a 'pairing telescope' for experimental investigation.

Abstract

Despite intense efforts during the last 25 years, the physics of unconventional superconductors, including the cuprates with a very high transition temperature, is still a controversial subject. It is believed that superconductivity in many of these strongly correlated metallic systems originates in the physics of quantum phase transitions, but quite diverse perspectives have emerged on the fundamentals of the electron-pairing physics, ranging from Hertz style critical spin fluctuation glue to the holographic superconductivity of string theory. Here we demonstrate that the gross energy scaling differences that are behind these various pairing mechanisms are directly encoded in the frequency and temperature dependence of the dynamical pair susceptibility. This quantity can be measured directly via the second order Josephson effect and it should be possible employing modern experimental techniques to build a `pairing telescope' that gives a direct view on the origin of quantum critical superconductivity.