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

Strong spin-phonon coupling unveiled by coherent phonon oscillations in Ca2RuO4

Min-Cheol Lee, Choong H. Kim, Inho Kwak, C. W. Seo, Changhee Sohn, F. Nakamura, C. Sow, Y. Maeno, E.-A. Kim, T. W. Noh, and K. W. Kim
Phys. Rev. B 99, 144306 – Published 15 April 2019
PDFHTMLExport Citation
Abstract
Corrections
Authors
Article Text
  • ACKNOWLEDGMENTS
    • Supplemental Material
    References

    Abstract

    We utilize near-infrared femtosecond pulses to investigate coherent phonon oscillations of Ca2RuO4. The coherent Ag phonon mode of the lowest frequency changes abruptly not only its amplitude but also the oscillation phase as the spin order develops. In addition, the phonon mode shows a redshift entering the magnetically ordered state, which indicates a spin-phonon coupling in the system. Density functional theory calculations reveal that the Ag oscillations result in octahedral tilting distortions, which are exactly in sync with the lattice deformation driven by the magnetic ordering. We suggest that the structural distortions by the spin-phonon coupling can induce the unusual oscillation phase shift between impulsive and displacive type oscillations.

    • Figure
    • Figure
    • Figure
    • Figure
    • Received 17 December 2017
    • Revised 3 June 2018
    • Corrected 21 November 2019

    DOI:https://doi.org/10.1103/PhysRevB.99.144306

    ©2019 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Phonons
    1. Physical Systems
    AntiferromagnetsMott insulators
    1. Techniques
    DFT+UUltrafast pump-probe spectroscopy
    Condensed Matter, Materials & Applied Physics

    Corrections

    21 November 2019

    Correction: The second KRF project number contained an error and has been fixed.

    Authors & Affiliations

    Min-Cheol Lee1,2, Choong H. Kim1,2, Inho Kwak1,2, C. W. Seo1,3, Changhee Sohn1,2, F. Nakamura4, C. Sow5, Y. Maeno5, E.-A. Kim6, T. W. Noh1,2,*, and K. W. Kim3,*

    • 1Center for Correlated Electron Systems (CCES), Institute for Basic Science (IBS), Seoul 08826, Republic of Korea
    • 2Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea
    • 3Department of Physics, Chungbuk National University, Cheongju, Chungbuk 28644, Republic of Korea
    • 4Department of Education and Creation Engineering, Kurume Institute of Technology, Fukuoka 830-0052, Japan
    • 5Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
    • 6Department of Physics, Cornell University, Ithaca, New York 14853, USA

    • *Corresponding authors: twnoh@snu.ac.kr; kyungwan.kim@gmail.com

    Article Text (Subscription Required)

    Click to Expand

    Supplemental Material (Subscription Required)

    Click to Expand

    References (Subscription Required)

    Click to Expand
    Issue

    Vol. 99, Iss. 14 — 1 April 2019

    Reuse & Permissions
    Access Options
    CHORUS

    Article Available via CHORUS

    Download Accepted Manuscript
    Author publication services for translation and copyediting assistance advertisement

    Authorization Required

    Log In
    Other Options
    ×

    Images

    • Figure 1
      Figure 1

      Generation mechanisms of coherent oscillations. Whereas the impulsive stimulated Raman scattering does not alter the average lattice coordinates, a displacive excitation can cause a shift of the coordinates in the excited state (from Q0 to Q0ex). There should be light absorption to generate the displacive oscillations, while the impulsive ones require no absorption.

      Reuse & Permissions
    • Figure 2
      Figure 2

      Temperature-dependent photoinduced reflectivity changes normalized by maximum values (ΔR)norm. Photoinduced reflectivity is measured at every 20 K (a) from 30 to 110 K (T≲TN) and (b) from 110 to 170 K (T≳TN).

      Reuse & Permissions
    • Figure 3
      Figure 3

      The (a) coherent phonon oscillations of photoinduced reflectivity after subtracting the electronic response by means of biexponential decay fits at temperatures of every 20 K from 30 to 170 K. The red arrow in (a) indicates the same delay time marked by an arrow in Fig. 2. (b) Fourier transform of the oscillations in (a). All the oscillating components correspond to the Ag symmetric Raman modes. (c)–(e) T-dependent fitting parameters of the frequency, amplitude, and phase of the lowest-frequency mode extracted from damped harmonic oscillator model fits. (f) The oscillating component and fit curves for the lowest-frequency mode. Higher frequency oscillations have been subtracted by using the model fits. Dotted vertical lines contrast the oscillation phases at different temperatures.

      Reuse & Permissions
    • Figure 4
      Figure 4

      (a) Eigenmode of the lowest Ag phonon derived by DFT calculations. The depicted vibration of the Ag mode +ΔQph corresponds to the direction represented by arrows in (b). (b) Positions of the apical (OA) and in-plane oxygen (OP) atoms noted in (a) expected from the DFT calculations under various spin configurations. All the position values are normalized by each unit cell length. The displacements of both oxygen atoms from the PM phase (black diamond) to the AFM phase (black triangle) are close to the motion of the lowest Ag phonon with an amplitude of 0.015 (0.011) Å in OA(OP) (+ΔQph; red arrows).

      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
    ×