Broadband Terahertz Time-domain Spectroscopy of Quantum Materials in a Dilution Refrigerator

TL;DR

This paper presents a terahertz spectroscopy system integrated with a dilution refrigerator and magnet, enabling low-temperature measurements of quantum materials, revealing an effective mass larger than bulk values.

Contribution

The work introduces a novel terahertz time-domain spectroscopy setup capable of operating at millikelvin temperatures with magnetic fields, applied to quantum well samples.

Findings

Measured cyclotron resonance at 145 mK and up to 6 T

Determined effective mass of 0.073 m_e, larger than bulk

Demonstrated system's capability for quantum material studies

Abstract

We have constructed a terahertz time domain spectroscopy system using a Bluefors dilution refrigerator with a 7 T split-coil magnet. Using a gallium arsenide single quantum well sample, terahertz waveforms were measured at 145 mK in a magnetic field range from 0 to 6 Tesla to measure cyclotron resonance. Effective mass is found to be $0.073 m_{e}$, which is larger than the commonly accepted bulk value of $0.068 m_{e}$.