THz frequency spectroscopy of solids

Possible fields of research are determined by the frequency range.

  • Inter-molecular vibrations: large mass, soft spring, can be studied in transmission (T) or in reflection (R) mode
  • Soft modes in structural phase transitions (T & R)
  • Scattering rate of charge carriers in metals and in highly correlated electron systems (R)
  • Superconducting gap (R or T for thin films)
  • Cyclotron resonance in semiconductors (T)
  • Electron energy levels in confined systems: quantum dots, 2D electron gas, etc. (T)
  • Electron spin resonance, where for free electrons 1Tesla=1cm-1 (T)
  • Spin-gap excitations (T)

At terahertz frequencies optics meets the magnetic resonance. For example, in an absorption spectrum in the applied magnetic field the light absorption induced by the magnetic component (electron spin resonance) and by electric component (e.g., interaction with lattice vibrations) of the light can be observed simultaneously.