Subpicosecond spin dynamics of excited states in the topological insulator Bi2Te3

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F49777513%3A23640%2F17%3A43932274" target="_blank" >RIV/49777513:23640/17:43932274 - isvavai.cz</a>

Result on the web

<a href="http://hdl.handle.net/11025/29235" target="_blank" >http://hdl.handle.net/11025/29235</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1103/PhysRevB.95.125405" target="_blank" >10.1103/PhysRevB.95.125405</a>

Result language

angličtina

Original language name

Subpicosecond spin dynamics of excited states in the topological insulator Bi2Te3

Original language description

Using time-, spin-, and angle-resolved photoemission, we investigate the ultrafast spin dynamics of hot electrons on the surface of the topological insulator Bi2 Te3 following optical excitation by femtosecond-infrared pulses. We observe two surface-resonance states above the Fermi level coexisting with a transient population of Dirac fermions that relax in ∼2 ps. One state disperses up to ∼0.4 eV just above the bulk continuum, and the other one at ∼0.8 eV inside a projected bulk band gap. At the onset of the excitation, both states exhibit a reversed spin texture with respect to that of the transient Dirac bands, in agreement with our one-step photoemission calculations. Our data reveal that the high-energy state undergoes spin relaxation within ∼0.5 ps, a process that triggers the subsequent spin dynamics of both the Dirac cone and the low-energy state, which behave as two dynamically locked electron populations. We discuss the origin of this behavior by comparing the relaxation times observed for electrons with opposite spins to the ones obtained from a microscopic Boltzmann model of ultrafast band cooling introduced into the photoemission calculations. Our results demonstrate that the nonequilibrium surface dynamics is governed by electron-electron rather than electron-phonon scattering, with a characteristic time scale unambiguously determined by the complex spin texture of excited states above the Fermi level. Our findings reveal the critical importance of detecting momentum and energy-resolved spin textures with femtosecond resolution to fully understand the subpicosecond dynamics of transient electrons on the surface of topological insulators.

Czech name

—

Czech description

—

Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10302 - Condensed matter physics (including formerly solid state physics, supercond.)

Project

—

Continuities

O - Projekt operacniho programu

Publication year

2017

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Physical Review B

ISSN

2469-9950

e-ISSN

—

Volume of the periodical

95

Issue of the periodical within the volume

12

Country of publishing house

US - UNITED STATES

Number of pages

10

Pages from-to

—

UT code for WoS article

000396011200007

EID of the result in the Scopus database

2-s2.0-85014845786