Evidence of a structural quantum critical point in (Ca<sub><i>x</i></sub>Sr<sub>1-<i>x</i></sub>)<sub>3</sub>Rh<sub>4</sub>Sn<sub>13</sub> from a lattice dynamics study

ORAL

Abstract

The nonmagnetic quasiskutterudite (CaxSr1-x)3Rh4Sn13 represents a precious system to explore the interplay between structural instabilities and superconductivity by tuning the Ca concentration x [1-3]. We performed inelastic x-ray scattering to probe the phonon spectrum of (CaxSr1-x)3Rh4Sn13 for various calcium contents. We detected a complete phonon softening at the M point when approaching the structural transition temperature from above. Intriguingly, at x = 0.85, the energy squared of the soft mode at M extrapolates to zero at (-5.7 ± 7.7) K, providing the first compelling microscopic evidence of a structural quantum critical point (QCP) in (CaxSr1-x)3Rh4Sn13. The observed phonon softening around the M point provides the essential ingredient for realizing strong-coupling superconductivity near the structural QCP [4].

[1] S. K. Goh et al., PRL 114, 097002 (2015)
[2] W. C. Yu et al., PRL 115, 207003 (2015)
[3] Y. J. Hu et al., PRB 95, 155142 (2017)
[4] Y. W. Cheung et al., PRB 98, 161103 (R) (2018)

*Financially supported by RGC of Hong Kong, CUHK, NSFC, The MEXT Japan (No. 16H04131, No. 15H03697, No. 16K05031).
Experiements are carried out under approval of JASRI (Proposal No. 2013B1095, 2015B1294, 2016A1160, 2017A1130, 2017B1228, 2018A1399).

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Presenters

  • Yiu Wing Cheung

    • Department of Physics, The Chinese University of Hong Kong

Authors

  • Yiu Wing Cheung

    • Department of Physics, The Chinese University of Hong Kong

  • Yajian Hu

    • Department of Physics, The Chinese University of Hong Kong
    • Physics, The Chinese University of Hong Kong

  • Masaki Imai

    • Department of Chemistry, Kyoto University

  • Yasuaki Tanioku

    • Department of Chemistry, Kyoto University

  • Hibiki Kanagawa

    • Department of Chemistry, Kyoto University

  • Joichi Murakawa

    • Department of Chemistry, Kyoto University

  • Kodai Moriyama

    • Department of Chemistry, Kyoto University

  • Wei Zhang

    • Department of Physics, The Chinese University of Hong Kong

  • Kwing To Lai

    • Department of Physics, The Chinese University of Hong Kong

  • Kazuyoshi Yoshimura

    • Department of Chemistry, Kyoto University

  • Malte Grosche

    • Cavendish Laboratory, University of Cambridge

  • Koji Kaneko

    • Japan Atomic Energy Agency
    • Materials Sciences Research Center, Japan Atomic Energy Agency

  • Satoshi Tsutsui

    • Japan Synchrotron Radiation Research Institute

  • Swee Kuan Goh

    • Department of Physics, The Chinese University of Hong Kong
    • Physics, The Chinese University of Hong Kong