Ultrafast surface Dirac fermion dynamics of SbTe-based topological insulators

SbTe系トポロジカル絶縁体の超高速表面ディラックフェルミオンダイナミクス

角田 一樹   ; 石田 行章*; Gdde, J.*; Hfer, U.*; Shin, S.*; 木村 昭夫*

Sumida, Kazuki; Ishida, Yukiaki*; Gdde, J.*; Hfer, U.*; Shin, S.*; Kimura, Akio*

Topological insulators (TIs) characterized by gapless and spin-polarized band dispersion on their surfaces have been extensively studied over the last decade. This article reviews our recent works on ultrafast carrier dynamics of SbTe-based nonmagnetic and magnetic TIs by utilizing state-of-the-art femtosecond time- and angle-resolved photoelectron spectroscopy. We have demonstrated that the electronic recovery time elongated from a few ps to 400 ps in the series of (SbBi)Te. We also investigated how the magnetic-impurity affects the carrier dynamics in ferromagnetic SbVTe. It was found that the electronic recovery time drastically shortened from a few ps to 500 fs with increasing vanadium concentration. Since the lifetime of the nonequilibrated surface Dirac fermions can range from femto- to nano-second, SbTe-based TIs would be promising for ultrafast spin switching and spin-polarized current generation device applications.