Ultrafast dynamics. Attosecond band-gap dynamics in silicon

Martin Schultze; Krupa Ramasesha; C D Pemmaraju; S A Sato; D Whitmore; A Gandman; James S Prell; L J Borja; D Prendergast; K Yabana; Daniel M Neumark; Stephen R Leone

doi:10.1126/science.1260311

Ultrafast dynamics. Attosecond band-gap dynamics in silicon

Science. 2014 Dec 12;346(6215):1348-52. doi: 10.1126/science.1260311.

Authors

Affiliations

¹ Department of Chemistry, University of California, Berkeley, CA 94720, USA. Fakultät für Physik, Ludwig-Maximilians-Universität, Am Coulombwall 1, D-85748 Garching, Germany. martin.schultze@mpq.mpg.de dneumark@berkeley.edu srl@berkeley.edu.
² Department of Chemistry, University of California, Berkeley, CA 94720, USA.
³ The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
⁴ Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan.
⁵ Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan. Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8577, Japan.
⁶ Department of Chemistry, University of California, Berkeley, CA 94720, USA. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. martin.schultze@mpq.mpg.de dneumark@berkeley.edu srl@berkeley.edu.
⁷ Department of Chemistry, University of California, Berkeley, CA 94720, USA. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. Department of Physics, University of California, Berkeley, CA 94720, USA. martin.schultze@mpq.mpg.de dneumark@berkeley.edu srl@berkeley.edu.

PMID: 25504716
DOI: 10.1126/science.1260311

Abstract

Electron transfer from valence to conduction band states in semiconductors is the basis of modern electronics. Here, attosecond extreme ultraviolet (XUV) spectroscopy is used to resolve this process in silicon in real time. Electrons injected into the conduction band by few-cycle laser pulses alter the silicon XUV absorption spectrum in sharp steps synchronized with the laser electric field oscillations. The observed ~450-attosecond step rise time provides an upper limit for the carrier-induced band-gap reduction and the electron-electron scattering time in the conduction band. This electronic response is separated from the subsequent band-gap modifications due to lattice motion, which occurs on a time scale of 60 ± 10 femtoseconds, characteristic of the fastest optical phonon. Quantum dynamical simulations interpret the carrier injection step as light-field-induced electron tunneling.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.