Polaronic quasiparticle picture for generation dynamics of coherent phonons in semiconductors: Transient and nonlinear Fano resonance

Yohei Watanabe, Ken-ichi Hino, Muneaki Hase, and Nobuya Maeshima
Phys. Rev. B 95, 014301 – Published 3 January 2017
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Abstract

We examine generation dynamics of coherent phonons in both polar and nonpolar semiconductors, such as GaAs and Si, based on a polaronic-quasiparticle (PQ) model. In this model, the PQ operator is composed of two kinds of operators: one is a quasiboson operator, defined as a linear combination of a set of pairs of electron operators, and the other is a longitudinal optical (LO) phonon operator. In particular, the problem of transient and nonlinear Fano resonance (FR) is tackled, where the vestige of this quantum interference effect was observed exclusively in lightly n-doped Si immediately after carriers were excited by an ultrashort pulse laser [M. Hase et al., Nature (London) 426, 51 (2003)], although not observed yet in GaAs. The PQ model enables us to show straightforwardly that the phonon energy state is embedded in continuum states formed by a set of adiabatic eigenstates of the quasiboson; this energy configuration is a necessary condition of the manifestation of the transient FR in the present optically nonlinear system. Numerical calculations are done for photoemission spectra relevant to the retarded longitudinal dielectric function of transient photoexcited states and for power spectra relevant to the LO-phonon displacement function of time. The photoemission spectra show that in undoped Si, an asymmetric spectral profile characteristic of FR comes into existence immediately after the instantaneous carrier excitation to fade out gradually, whereas in undoped GaAs, no asymmetry in spectra appears in the whole temporal region. The similar results are also obtained in the power spectra. These results are in harmony with the reported experimental results. It is found that the obtained difference in spectral profile between undoped Si and GaAs is attributed to a phase factor of an effective interaction between the LO phonon and the quasiboson. More detailed discussion of the FR dynamics is made in the text.

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  • Received 15 September 2015
  • Revised 7 October 2016

DOI:https://doi.org/10.1103/PhysRevB.95.014301

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Yohei Watanabe1, Ken-ichi Hino2,3,*, Muneaki Hase4, and Nobuya Maeshima2,3

  • 1Doctoral Program in Materials Science, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
  • 2Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Japan
  • 3Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8577, Japan
  • 4Division of Applied Physics, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573, Japan

  • *hino@ims.tsukuba.ac.jp

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Issue

Vol. 95, Iss. 1 — 1 January 2017

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