Observation of ultrafast carrier dynamics in MnBi_2-xSb_xTe₄(x=0.19) magnetic topological insulator

Ricky Tsai^2*, Jiunn-Yuan Lin², Chih-Wei Luo¹, Nidhi Puri², Chien-Ming Tu¹, Wen-Yen Tzeng¹, Cheng-Chien Chen³, Jiun-Haw Chu⁴

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu City, Taiwan
²Institute of Physics, National Yang Ming Chiao Tung University, Hsinchu City, Taiwan
³Department of Physics, University of Alabama at Birmingham, State of Alabama, USA
⁴Department of Physics, University of Washington, Seattle,State of Washington, USA

* Presenter:Ricky Tsai, email:godtsai310195@gmail.com

MnBi₂Te₄ is recently identified as an intrinsic antiferromagnetic (AFM) topological insulator whose possible behavior and ultrafast dynamics could be investigated through a versatile femtosecond time-resolved spectroscopy under applied magnetic field and temperature. In this experiment, topological quantum phase transition is studied in the magnetic topological insulator MnBi_2-xSb_xTe₄(x=0.19), and focus on the phase transition induced by magnetic field, chemical substitution, and ultrafast lasers. The optical pump-probe (OP-OP) measurements are performed in the magneto-optical closed-cycle cryostat (Opti-Cool) to reveal and study the ultrafast dynamics about MnBi_2-xSb_xTe₄(x=0.19) at room temperature and low temperature (2 K). A continuously increasing magnetic field to 7 T is also applied during the low temperature condition to observe the possible change of ultrafast dynamics crossing the spin-flop situation. Additionally, we also arrange to perform the Superconducting Quantum Interference Device (SQUID) to confirm the magnetic moment of anti-ferromagnetic state at Neel temperature.
We are grateful to NSTC of Taiwan and AFOSR of US for supporting this project (NSTC-110-2124-M-A49-007-MY3).

Keywords: ultrafast carrier dynamics, femtosecond time-resolved spectroscopy, magnetic topological insulator