Clarifying Ultrafast Carrier Dynamics in Ultrathin Films of the Topological Insulator Bi2Se3Using Transient Absorption Spectroscopy

Glinka，Yuri D.1,2; Li，Junzi3; He，Tingchao3; Sun，Xiao Wei1,4

2021

10.1021/acsphotonics.1c00115

ACS Photonics   影响因子和分区

2330-4022

Ultrafast carrier dynamics in the topological insulator Bi2Se3 have recently been intensively studied using a variety of techniques. However, we are not aware of any successful experiments exploiting transient absorption (TA) spectroscopy for these purposes. Here we demonstrate that if the ∼730 nm wavelength pumping (∼1.7 eV photon energy) is applied to ultrathin Bi2Se3 films, TA spectra cover the entire visible region, thus unambiguously pointing to two-photon excitation (∼3.4 eV). The carrier relaxation dynamics is found to be governed by the polar optical phonon cascade emission occurring in both the bulk states and the Dirac surface states (SS), including SS-bulk-SS vertical electron transport and being also exclusively influenced by whether the Dirac point is presented between the Dirac cones of the higher energy (∼1.5 eV) Dirac SS (known as SS2). We have recognized that SS2 act as a valve substantially slowing down the relaxation of electrons when the gap between Dirac cones exceeds the polar optical phonon and resonant defect energies. The resulting progressive accumulation of electrons in the gapped SS2 becomes detectable through the inverse-bremsstrahlung-type free carrier absorption.

carrier relaxation rates electron-phonon coupling free carrier absorption topological insulator topologically protected surface states ultrafast carrier dynamics

SCI ; EI

英语

第一 ; 通讯

WOS:000643600400031

20211910309665

Absorption spectroscopy ; Dynamics ; Electric insulators ; Electron transport properties ; Phonons ; Photons ; Selenium compounds ; Topological insulators ; Ultrathin films

Atomic and Molecular Physics:931.3

2-s2.0-85105097404

Scopus

1.Guangdong University Key Lab for Advanced Quantum Dot Displays and Lighting,Shenzhen Key Laboratory for Advanced Quantum Dot Displays and Lighting,Department of Electrical and Electronic Engineering,Southern University of Science and Technology,Shenzhen,518055,China
2.Institute of Physics,National Academy of Sciences of Ukraine,Kiev,03028,Ukraine
3.College of Physics and Energy,Shenzhen University,Shenzhen,518060,China
4.Shenzhen Planck Innovation Technologies Pte Ltd.,Longgang, Shenzhen,518112,China

Glinka，Yuri D.,Li，Junzi,He，Tingchao,et al. Clarifying Ultrafast Carrier Dynamics in Ultrathin Films of the Topological Insulator Bi2Se3Using Transient Absorption Spectroscopy[J]. ACS Photonics,2021,8:1191-1205.

Glinka，Yuri D.,Li，Junzi,He，Tingchao,&Sun，Xiao Wei.(2021).Clarifying Ultrafast Carrier Dynamics in Ultrathin Films of the Topological Insulator Bi2Se3Using Transient Absorption Spectroscopy.ACS Photonics,8,1191-1205.

Glinka，Yuri D.,et al."Clarifying Ultrafast Carrier Dynamics in Ultrathin Films of the Topological Insulator Bi2Se3Using Transient Absorption Spectroscopy".ACS Photonics 8(2021):1191-1205.