Ultrafast multi-cycle terahertz measurements of the electrical conductivity in strongly excited solids

Zhijiang Chen ,R Zhang,J B Kim,J Schein,M Gauthier,S Toleikis,B B L Witte,S H Glenzer,R Redmer,C B Curry,Catherine Burcklen ,Stefan P Hau‐Riege ,Régina Soufli ,Saša Bajt ,Anthea Weinmann ,Benjamin K Ofori-Okai ,Lars Seipp ,Rui Pan ,Nikola Stojanović ,Mianzhen Mo ,Ying Y Tsui ,Ekaterina Zapolnova ,Sergey Usenko ,F Treffert,T Pardini

doi:10.1038/s41467-021-21756-6

Abstract

Key insights in materials at extreme temperatures and pressures can be gained by accurate measurements that determine the electrical conductivity. Free-electron laser pulses can ionize and excite matter out of equilibrium on femtosecond time scales, modifying the electronic and ionic structures and enhancing electronic scattering properties. The transient evolution of the conductivity manifests the energy coupling from high temperature electrons to low temperature ions. Here we combine accelerator-based, high-brightness multi-cycle terahertz radiation with a single-shot electro-optic sampling technique to probe the evolution of DC electrical conductivity using terahertz transmission measurements on sub-picosecond time scales with a multi-undulator free electron laser. Our results allow the direct determination of the electron-electron and electron-ion scattering frequencies that are the major contributors of the electrical resistivity.

Highlights

Key insights in materials at extreme temperatures and pressures can be gained by accurate measurements that determine the electrical conductivity
While optical and x-ray free electron lasers (FEL) routinely provide a suitable temporal resolution in the femtosecond regime, their utility for determining the conductivity is limited because the information is convoluted by the oscillating fields of the electromagnetic waves, whose frequencies are comparable to or larger than the electron scattering rates
The experiment was performed at Deutsches ElektronenSYnchrotron (DESY) Free-electron LASer in Hamburg (FLASH) facility, where two sets of undulators provided synchronized extreme-ultraviolet (XUV)-FEL and THz-FEL pulses simultaneously[19,20,21,22], cf

Summary

Introduction

Key insights in materials at extreme temperatures and pressures can be gained by accurate measurements that determine the electrical conductivity. We apply electro-optics sampling to measure the THz time-domain electric-field waveform, E(t), in a single-shot using a separate 50 fs, 800 nm probe laser pulse.

Results

Conclusion