Multidimensional Terahertz Probes of Quantum Materials

TL;DR

This paper discusses the development and application of two-dimensional terahertz spectroscopy (2DTS) for studying quantum materials, highlighting its potential to reveal new physics and explore non-equilibrium states.

Contribution

It introduces 2DTS as a novel technique for probing quantum materials at terahertz frequencies and reviews recent experimental and theoretical advances in the field.

Findings

2DTS reveals unique quantum material spectra

Application of 2DTS to non-equilibrium states is promising

Rapid growth in experimental and theoretical studies

Abstract

Multidimensional spectroscopy has a long history originating from nuclear magnetic resonance, and has now found widespread application at infrared and optical frequencies as well. However, the energy scales of traditional multidimensional probes have been ill-suited for studying quantum materials. Recent technological advancements have now enabled extension of these multidimensional techniques to the terahertz frequency range, in which collective excitations of quantum materials are typically found. This Perspective introduces the technique of two-dimensional terahertz spectroscopy (2DTS) and the unique physics of quantum materials revealed by 2DTS spectra, accompanied by a selection of the rapidly expanding experimental and theoretical literature. While 2DTS has so far been primarily applied to quantum materials at equilibrium, we provide an outlook for its application towards understanding their dynamical non-equilibrium states and beyond.