Transient phonon vacuum squeezing due to femtosecond-laser-induced bond hardening

Fairoja Cheenicode Kabeer, Naira S. Grigoryan, Eeuwe S. Zijlstra, and Martin E. Garcia
Phys. Rev. B 90, 104303 – Published 15 September 2014

Abstract

Ultrashort optical pulses can be used both to create fundamental quasiparticles in crystals and to change their properties. In noble metals, femtosecond lasers induce bond hardening, but little is known about its origin and consequences. Here we simulate ultrafast laser excitation of silver at high fluences. We compute laser-excited potential-energy surfaces by all-electron ab initio theory and analyze the resulting quantum lattice dynamics. We also consider incoherent lattice heating due to electron-phonon interactions using the generalized two-temperature model. We find phonon hardening, which we attribute to the excitation of s electrons. We demonstrate that this may result in phonon vacuum squeezed states with an optimal squeezing factor of 0.001 at the L-point longitudinal mode. This finding implies that ultrafast laser-induced bond hardening may be used as a tool to manipulate the quantum state of opaque materials, where, so far, the squeezing of phonons below the zero-point motion has only been realized in transparent crystals by a different mechanism. On the basis of our finding, we further propose a method for directly measuring bond hardening.

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  • Received 20 December 2012
  • Revised 9 July 2014

DOI:https://doi.org/10.1103/PhysRevB.90.104303

©2014 American Physical Society

Authors & Affiliations

Fairoja Cheenicode Kabeer*, Naira S. Grigoryan, Eeuwe S. Zijlstra, and Martin E. Garcia

  • Theoretische Physik, Universität Kassel and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), Heinrich-Plett-Straße 40, 34132 Kassel, Germany

  • *fairu.ck@gmail.com

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Issue

Vol. 90, Iss. 10 — 1 September 2014

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