Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                

Transient hot electron dynamics in single-layer TaS2

Federico Andreatta, Habib Rostami, Antonija Grubišić Čabo, Marco Bianchi, Charlotte E. Sanders, Deepnarayan Biswas, Cephise Cacho, Alfred J. H. Jones, Richard T. Chapman, Emma Springate, Phil D. C. King, Jill A. Miwa, Alexander Balatsky, Søren Ulstrup, and Philip Hofmann
Phys. Rev. B 99, 165421 – Published 16 April 2019
PDFHTMLExport Citation
Abstract
Authors
Article Text
  • INTRODUCTION
  • EXPERIMENTAL
  • RESULTS AND DISCUSSION
  • CONCLUSIONS
  • ACKNOWLEDGMENTS
    • Supplemental Material
    References

    Abstract

    Using time- and angle-resolved photoemission spectroscopy, we study the response of metallic single-layer TaS2 in the 1H structural modification to the generation of excited carriers by a femtosecond laser pulse. A complex interplay of band structure modifications and electronic temperature increase is observed and analyzed by direct fits of model spectral functions to the two-dimensional (energy and k-dependent) photoemission data. Upon excitation, the partially occupied valence band is found to shift to higher binding energies by up to ≈100meV, accompanied by electronic temperatures exceeding 3000 K. These observations are explained by a combination of temperature-induced shifts of the chemical potential, as well as temperature-induced changes in static screening. Both contributions are evaluated in a semiempirical tight-binding model. The shift resulting from a change in the chemical potential is found to be dominant.

    • Figure
    • Figure
    • Figure
    • Figure
    • Figure
    • Figure
    • Figure
    • Received 23 January 2019

    DOI:https://doi.org/10.1103/PhysRevB.99.165421

    ©2019 American Physical Society

    Physics Subject Headings (PhySH)

    1. Physical Systems
    2-dimensional systemsTwo-dimensional electron system
    1. Techniques
    Many-body techniquesTight-binding modelTime & angle resolved photoemission spectroscopy
    Condensed Matter, Materials & Applied Physics

    Authors & Affiliations

    Federico Andreatta1,*, Habib Rostami2,*, Antonija Grubišić Čabo1, Marco Bianchi1, Charlotte E. Sanders3, Deepnarayan Biswas4, Cephise Cacho3, Alfred J. H. Jones3, Richard T. Chapman3, Emma Springate3, Phil D. C. King4, Jill A. Miwa1, Alexander Balatsky2,5, Søren Ulstrup1, and Philip Hofmann1,†

    • 1Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark
    • 2Nordita, 106 91 Stockholm, Sweden
    • 3Central Laser Facility, STFC Rutherford Appleton Laboratory, Harwell, United Kingdom
    • 4SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, United Kingdom
    • 5Institute for Materials Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

    • *These authors contributed equally to this work.
    • †philip@phys.au.dk

    Article Text (Subscription Required)

    Click to Expand

    Supplemental Material (Subscription Required)

    Click to Expand

    References (Subscription Required)

    Click to Expand
    Issue

    Vol. 99, Iss. 16 — 15 April 2019

    Reuse & Permissions
    Access Options
    Author publication services for translation and copyediting assistance advertisement

    Authorization Required

    Log In
    Other Options
    ×

    Images

    • Figure 1
      Figure 1

      TR-ARPES measurement of the SL TaS2 dispersion around EF (sample temperature 300 K). (a) Left: measured spectrum before optical excitation (t<0). Right: energy distribution curve taken at the k value of the band's highest binding energy as given in the text. The dashed blue line is an estimate of the peak position. (b) Calculated dispersion from Ref. [32] with examples of possible direct electron (filled circles) and hole (open circles) excitation processes (arrows). The region enclosed by a green square marks the (E,k) space probed in the TR-ARPES experiment. (c) TR-ARPES data as in (a) but at the peak of optical excitation (t=40 fs). Right: energy distribution curve taken as in (a). (d) Difference spectrum: intensity difference obtained by subtracting the intensity for t<0 in (a) from that at t=40 fs in (c).

      Reuse & Permissions
    • Figure 2
      Figure 2

      (a) Static ARPES data of the SL TaS2 parabolic state with the band minimum located at kmin and the Fermi level crossing at kF. (b) Modelled intensity over the measured region of (E,k) space shown in (a). [(c) and (d)] Example EDCs of the measured data and intensity fit taken along the dashed vertical lines shown in (a) and (b) at (d) kF and (e) kmin, respectively. The background intensity in the fit is shown as a light gray line marked “BG.”

      Reuse & Permissions
    • Figure 3
      Figure 3

      Time dependence of the excited-state signal in SL TaS2 and spectral function simulations: [(a)–(c)] TR-ARPES data obtained at the given time delays for an optical excitation energy of 2.05 eV and a pump laser fluence of 7.8mJ/cm2 with the sample at a temperature of 300 K. The spectrum in (a) was taken before optical excitation. The fitted parabolic dispersions derived according to Eq. (2) are shown on top of the spectra and coloured to distinguish the different time delays. [(d) and (e)] Difference spectra determined by subtracting the equilibrium spectrum in (a) from the excited state spectra in (b) and (c). [(f)–(j)] Simulated intensity (difference) corresponding to the measured data in (a)–(e). [(k) and (l)] Comparison of EDCs from measurements (symbols) and simulations (lines) at kF and kmin, respectively [see pink and purple lines in (f)].

      Reuse & Permissions
    • Figure 4
      Figure 4

      Extracted parameters from the data set shown in Fig. 3. (a) Time dependence of the extracted band shift ΔW. The fit to a double exponential function is shown (solid line) and the relaxation times τ1 and τ2 are given. (b) Corresponding data and fit for the electron temperature Te.

      Reuse & Permissions
    • Figure 5
      Figure 5

      Temperature-induced band shift, using data for different choices of laser fluence and sample temperature. The data points show the extracted experimental band shift ΔW as a function of electronic temperature Te. The curves are the calculated change in the occupied bandwidth as a function of Te for three different values of the system's Fermi energy (chemical potential at Te=0.)

      Reuse & Permissions
    • Figure 6
      Figure 6

      (a) Calculated single-particle dispersion of the topmost valence band of SL TaS2. The solid line is the result from a tight-binding calculation with parameters fitted to a density functional theory calculation (dashed line). Note that the bands are spin-split at K¯. The dashed black line shows the position of the Fermi energy for a filling of the band with one electron per unit cell, as expected for the free-standing layer. (b) Resulting density of states. (c) Chemical potential versus the Fermi energy at different values of Te with Γkσ=10meV and Σkσ=0. (d) The chemical potential shift versus Te for three different values of the Fermi energy. Solid (dashed) curves correspond to the absence (presence) of self-energy effects on the chemical potential.

      Reuse & Permissions
    • Figure 7
      Figure 7

      (a) Calculated temperature-dependent electronic susceptibility along high-symmetry lines of the BZ for four different values of Te. (b) Real part of the electronic self-energy along high-symmetry lines of the BZ[Te as in (a)]. Note that the difference between up and down spins is negligible for this set of parameters (i.e., Σk↑∼Σk↓). Note that for this figure, we set EF=430meV.

      Reuse & Permissions
    ×

    Sign up to receive regular email alerts from Physical Review B

    Log In

    Cancel
    ×

    Search

    Article Lookup

    Paste a citation or DOI
    Enter a citation
    ×