Nonlinear Processes in Condensed Matter Driven by Terahertz Fields

The advent of intense, subpicosecond laser pulses at terahertz (THz) frequencies has revolutionized THz spectroscopy, enabling detailed investigations of physical, chemical, and biological systems. These advancements have also paved the way for time-resolved measurements, where THz pulses probe the dynamic response following optical excitation. Even under non-resonant conditions, intense THz pulses can trigger highly nonlinear phenomena. For instance, THz electric fields can accelerate valence electrons into the conduction band, enhancing conductivity in semiconductors [1,2]. At even higher field strengths, tunneling can drive electrons directly from the valence to the conduction band [3,4].

In this colloquium, I will delve into the origins of THz emission in non-centrosymmetric materials [5] and examine how intense THz pulses can trigger nonlinear processes in condensed matter systems [6]. In particular, I will explore how the interplay between intermolecular interactions and strong THz fields enables the manipulation of charge dynamics and dielectric properties in aqueous systems [7,8].
 

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