Professor Mark Sherwin
Department of Physics and
Institute for Terahertz Science and Technology (ITST),
University of California, Santa Barbara

Electric and Magnetic Resonance at Terahertz Frequencies

Abstract:

Nonlinear and time-resolved spectroscopies based on manipulating electric charges and magnetic dipoles in condensed matter are relatively widespread at radio and microwave frequencies (<10¹¹Hz =0.1 THz), as well as at infrared and optical frequencies (> 30 THz). The difficulty of generating high-power, coherent radiation between ~0.1 and 30 THz has limited such spectroscopies in this so-called “terahertz gap.” The bulk of the talk will focus near-ir spectroscopy of undoped quantum wells driven by intense terahertz fields. The lowest excitonic absorption splits and shifts under the influence of strong terahertz excitation. A full explanation of the data requires a theoretical treatment that goes beyond the rotating wave and two-level approximations that are familiar from standard treatments of quantum systems in oscillating fields. As a preview of coming attractions, I will also introduce the 0.24 THz free-electron-laser-based pulsed electron paramagnetic resonance spectrometer that is under development at UCSB.