Two-photon IR pumped UV-Vis transient absorption spectroscopy of Dirac fermions in the topological insulator Bi2Se3

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

2022-09-19

10.1088/1361-648X/ac90a7

JOURNAL OF PHYSICS-CONDENSED MATTER   Impact Factor & Quartile

0953-8984

1361-648X

It is often taken for granted that in pump-probe experiments on the topological insulator (TI) Bi2Se3using IR pumping with a commercial Ti:sapphire laser [∼800 nm (1.55 eV photon energy)], the electrons are excited in the one-photon absorption regime, even when pumped with absorbed fluences in the mJ cm-2range. Here, using UV-Vis transient absorption (TA) spectroscopy, we show that even at low-power Infrared (IR) pumping with absorbed fluences in theμJ cm-2range, the TA spectra of the TI Bi2Se3extend across a part of the UV and the entire visible region. This observation suggests unambiguously that the two-photon pumping regime accompanies the usual one-photon pumping regime even at low laser powers applied. We attribute the high efficiency of two-photon pumping to the giant nonlinearity of Dirac fermions in the Dirac surface states (SS). On the contrary, one-photon pumping is associated with the excitation of bound valence electrons in the bulk into the conduction band. Two mechanisms of absorption bleaching were also revealed since they manifest themselves in different spectral regions of probing and cause the appearance of three different relaxation dynamics. These two mechanisms were attributed to the filling of the phase-space in the Dirac SS and bulk states, followed by the corresponding Pauli blocking.

2D Dirac systems topological insulators transient absorption ultrafast

SCI

English

First

National Key Research and Development Program of China[2016YFB0401702] ; Shenzhen Peacock Team Project[KQTD2016030111203005] ; Shenzhen Key Laboratory for Advanced Quantum Dot Displays and Lighting[ZDSYS201707281632549]

Physics

Physics, Condensed Matter

WOS:000857870200001

IOP Publishing Ltd

PHYSICS

2-s2.0-85138460663

Scopus

1.Guangdong University Key Laboratory 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,03028,Ukraine
3.College of Physics and Energy,Shenzhen University,Shenzhen,518060,China
4.Shenzhen Planck Innovation Technologies Pte Ltd,Shenzhen,518112,China

Glinka，Yuri D.,He，Tingchao,Sun，Xiao Wei. Two-photon IR pumped UV-Vis transient absorption spectroscopy of Dirac fermions in the topological insulator Bi2Se3[J]. JOURNAL OF PHYSICS-CONDENSED MATTER,2022,34(46).

Glinka，Yuri D.,He，Tingchao,&Sun，Xiao Wei.(2022).Two-photon IR pumped UV-Vis transient absorption spectroscopy of Dirac fermions in the topological insulator Bi2Se3.JOURNAL OF PHYSICS-CONDENSED MATTER,34(46).

Glinka，Yuri D.,et al."Two-photon IR pumped UV-Vis transient absorption spectroscopy of Dirac fermions in the topological insulator Bi2Se3".JOURNAL OF PHYSICS-CONDENSED MATTER 34.46(2022).