Relaxation of the resistive superconducting state in boron-doped diamond films

TL;DR

This study investigates the relaxation dynamics of the superconducting state in boron-doped diamond films, revealing a T^{-2} dependence of electron-phonon scattering time and increased relaxation times near T_c.

Contribution

It provides the first detailed measurement of energy relaxation times in boron-doped diamond superconductors using AMAR technique.

Findings

Electron-phonon scattering time varies as T^{-2} between 1.7 and 2.2 K.

Relaxation time increases as temperature approaches T_c from below and above.

High-frequency rolloff indicates the characteristic energy relaxation time in the material.

Abstract

We report a study of the relaxation time of the restoration of the resistive superconducting state in single crystalline boron-doped diamond using amplitude-modulated absorption of (sub-)THz radiation (AMAR). The films grown on an insulating diamond substrate have a low carrier density of about 2.5x10^{21} cm^{-3} and a critical temperature of about 2 K. By changing the modulation frequency we find a high-frequency rolloff which we associate with the characterstic time of energy relaxation between the electron and the phonon systems or the relaxation time for nonequilibrium superconductivity. Our main result is that the electron-phonon scattering time varies clearly as T^{-2}, over the accessible temperature range of 1.7 to 2.2 K. In addition, we find, upon approaching the critical temperature T_c, evidence for an increasing relaxation time on both sides of T_c.