Light-Tunable Surface State and Hybridization Gap in Magnetic Topological Insulator MnBi$_8$Te$_{13}$

TL;DR

This study uses ultrafast spectroscopy to demonstrate that light can tune the surface states and interlayer interactions in the magnetic topological insulator MnBi$_8$Te$_{13}$, revealing potential for optical control of its electronic properties.

Contribution

It provides the first direct observation of light-induced modulation of surface states and hybridization gaps in MnBi$_8$Te$_{13}$ using time-resolved photoemission spectroscopy.

Findings

Photoinduced filling of the surface state hybridization gap.

Ultrafast electron and hole relaxation within 1-2 ps.

Light-tunable interlayer interaction in MnBi$_8$Te$_{13}$.

Abstract

MnBi$_8$Te$_{13}$ is an intrinsic ferromagnetic (FM) topological insulator with different complex surface terminations. Resolving the electronic structures of different termination surfaces and manipulation of the electronic state are important. Here, by using micrometer spot time- and angle-resolved photoemission spectroscopy ($\mu$-TrARPES), we resolve the electronic structures and reveal the ultrafast dynamics upon photoexcitation. Photoinduced filling of the surface state hybridization gap is observed for the Bi$_2$Te$_3$ quintuple layer directly above MnBi$_2$Te$_4$ accompanied by a nontrivial shift of the surface state, suggesting light-tunable interlayer interaction. Relaxation of photoexcited electrons and holes is observed within 1-2 ps. Our work reveals photoexcitation as a potential control knob for tailoring the interlayer interaction and surface state of MnBi$_8$Te$_{13}$.