Broadband terahertz time-domain spectroscopy of quantum materials in a dilution refrigerator

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 T to measure cyclotron resonance. The effective mass was found to be 0.073me, which is larger than the commonly accepted bulk value of 0.068me.