Evidence of a structural quantum critical point in (CaxSr1-x)3Rh4Sn13 from a lattice dynamics study
Physical Review B
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Cheung, Y., Hu, Y., Imai, M., Tanioku, Y., Kanagawa, H., Murakawa, J., Moriyama, K., et al. (2018). Evidence of a structural quantum critical point in (CaxSr1-x)3Rh4Sn13 from a lattice dynamics study. Physical Review B, 98 (16) https://doi.org/10.1103/PhysRevB.98.161103
Approaching a quantum critical point (QCP) has been an effective route to stabilize superconductivity. While the role of magnetic QCPs has been extensively discussed, similar exploration of a structural QCP is scarce due to the lack of suitable systems with a continuous structural transition that can be conveniently tuned to 0 K. Using inelastic x-ray scattering, we examine the phonon spectrum of the nonmagnetic quasiskutterudite (CaxSr1−x)3Rh4Sn13, which represents a precious system to explore the interplay between structural instabilities and superconductivity by tuning the Ca concentration x. We unambiguously detect the softening of phonon modes around the M point on cooling towards the structural transition. Intriguingly, at x=0.85, the soft mode energy squared at the M point extrapolates to zero at (−5.7±7.7) K, providing the first compelling microscopic evidence of a structural QCP in (CaxSr1−x)3Rh4Sn13. The enhanced phonon density of states at low energy provides the essential ingredient for realizing strong-coupling superconductivity near the structural QCP.
Is supplemented by: https://doi.org/10.17863/CAM.31763
External DOI: https://doi.org/10.1103/PhysRevB.98.161103
This record's URL: https://www.repository.cam.ac.uk/handle/1810/286509