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Title: Thickness-dependent electron–lattice equilibration in laser-excited thin bismuth films

Electron–phonon coupling processes determine electronic transport properties of materials and are responsible for the transfer of electronic excess energy to the lattice. With decreasing device dimensions an understanding of these processes in nanoscale materials is becoming increasingly important. We use time-resolved electron diffraction to directly study energy relaxation in thin bismuth films after optical excitation. Precise measurements of the transient Debye–Waller-effect for various film thicknesses and over an extended range of excitation fluences allow to separate different contributions to the incoherent lattice response. While phonon softening in the electronically excited state is responsible for an immediate increase of the r.m.s. atomic displacement within a few hundred fs, 'ordinary' electron–phonon coupling leads to subsequent heating of the material on a few ps time-scale. Moreover, the data reveal distinct changes in the energy transfer dynamics which becomes faster for stronger excitation and smaller film thickness, respectively. The latter effect is attributed to a cross-interfacial coupling of excited electrons to phonons in the substrate.
Authors:
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  1. Univ. of Duisburg-Essen (Germany)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-76SF00515
Type:
Published Article
Journal Name:
New Journal of Physics
Additional Journal Information:
Journal Volume: 17; Journal Issue: 11; Journal ID: ISSN 1367-2630
Publisher:
IOP Publishing
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; electron-phonon coupling; bismuth; thin films; time-resolved electron diffraction
OSTI Identifier:
1238985
Alternate Identifier(s):
OSTI ID: 1237587; OSTI ID: 1238989