Terahertz electrodynamics of Dirac fermions in topological insulators
Date : August 23, 2016 14:00 ~ 15:30
Speaker : Dr. Byung Cheol park (Max Planck Institute for Polymer Research)
Location : Bldg. 19, Rm. 210
Topological insulators (TIs)
are interesting quantum materials which have symmetry-protected surface states,
so called topological surface states (TSSs). The TSS features photon-like
energy-momentum dispersion and spin-momentum locked nature. As such, Dirac-like
quasiparticles on the TSS essentially possess ultrahigh mobility, emphasizing
the significance of the low-frequency transport measurements. Also, the heavy
atomic mass, accompanied by strong spin-orbit interaction, ensures the
emergence of long-wavelength phonon mode. Therefore, the investigation of
low-energy regime is crucial for understanding fundamental properties of Dirac
fermions and phonons, and their interplay in TIs. This talk aims to explore
low-energy electrodynamics of TI ultrathin films via terahertz (THz)
spectroscopy, leading to THz hallmarks of the TSSs. We initiate our discussion
with detection, isolation, and manipulation of the TSSs, all of which are at
the heart of current TI research. The presentation culminates in deliberations
on ultrafast phonon renormalization by hot Dirac fermions in the TSS,
indicating dynamical change in the electron-phonon interaction in TIs. This
seminar will introduce, discuss, and share recent key findings from THz
spectroscopy of TIs