Center for Correlated Electron Systems

Seminar

Terahertz electrodynamics of Dirac fermions in topological insulators

August 16, 2016l Hit 942
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