Frequency dependent relaxation rate in the superconducting YBa2Cu3O{6+delta}

TL;DR

This study investigates the frequency-dependent quasiparticle relaxation rate in YBa2Cu3O{6+delta} superconductors across various temperatures, revealing a transition from frequency independence to a power-law behavior as temperature decreases.

Contribution

It provides the first detailed analysis of the frequency dependence of the quasiparticle scattering rate in reduced YBa2Cu3O{6+delta} films over a broad temperature range.

Findings

1/tau*(nu) is frequency independent at high temperatures and low frequencies.

A power-law dependence 1/tau*~nu^{1.5} emerges at lower temperatures.

Temperature-dependent effective mass explains spectral weight changes above Tc.

Abstract

The submillimeter-wave 3 cm{-1} < nu < 35 cm{-1} complex conductivity of the reduced YBa2Cu3O{6+delta} film (Tc=56.5 K) was investigated for temperatures 4 K < T < 300 K and compared to the properties of the same film in the optimally doped state. The frequency dependence of the effective quasiparticle scattering rate 1/tau*(nu) was extracted from the spectra. 1/tau*(nu) is shown to be frequency independent at low frequencies and high temperatures. A gradual change to 1/tau*~nu^{1.5} law is observed as temperature decreases. In order to explain the observed temperature dependence of the low frequency spectral weight above Tc, the quasiparticle effective mass is supposed to be temperature dependent for T>Tc.