Kinetic Inductance and Penetration Depth of Thin Superconducting Films Measured by THz Pulse Spectroscopy

TL;DR

This study uses THz pulse spectroscopy to measure the transmission and kinetic inductance of thin YBCO superconducting films across a wide temperature range, providing insights into their penetration depth behavior.

Contribution

It introduces a method to determine the temperature-dependent London penetration depth of superconducting films using broadband THz pulses.

Findings

Measured the transmission of THz pulses through YBCO films from 10K to 300K.

Observed pulse reshaping below T_c due to kinetic inductance.

Found the penetration depth follows a specific temperature dependence with  = 148 nm and ^2 = 1 - (T/T_c)^2.

Abstract

We measure the transmission of THz pulses through thin films of YBCO at temperatures between 10K and 300K. The pulses possess a useable bandwidth extending from 0.1 -- 1.5 THz (3.3 cm^-1 -- 50 cm^-1). Below T_c we observe pulse reshaping caused by the kinetic inductance of the superconducting charge carriers. From transmission data, we extract values of the London penetration depth as a function of temperature, and find that it agrees well with a functional form (\lambda(0)/\lambda(T))^2 = 1 - (T/T_c)^{\alpha}, where \lambda(0) = 148 nm, and \alpha = 2. *****Figures available upon request*****