Softening of a flat phonon mode in the kagome ScV6Sn6

A Korshunov; H Hu; D Subires; Y Jiang; D Călugăru; X Feng; A Rajapitamahuni; C Yi; S Roychowdhury; M G Vergniory; J Strempfer; C Shekhar; E Vescovo; D Chernyshov; A H Said; A Bosak; C Felser; B Andrei Bernevig; S Blanco-Canosa

doi:10.1038/s41467-023-42186-6

Softening of a flat phonon mode in the kagome ScV₆Sn₆

Nat Commun. 2023 Oct 20;14(1):6646. doi: 10.1038/s41467-023-42186-6.

Authors

A Korshunov^#¹, H Hu^#², D Subires^#², Y Jiang^#^{3

4}, D Călugăru^#⁵, X Feng^#^{2

6}, A Rajapitamahuni⁷, C Yi⁶, S Roychowdhury⁶, M G Vergniory^{2

6}, J Strempfer⁸, C Shekhar⁶, E Vescovo⁷, D Chernyshov⁹, A H Said⁸, A Bosak¹, C Felser⁶, B Andrei Bernevig^{10

11

12}, S Blanco-Canosa^{13

14}

Affiliations

¹ European Synchrotron Radiation Facility (ESRF), BP 220, F-38043, Grenoble, France.
² Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal, 20018, San Sebastián, Spain.
³ Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
⁴ University of Chinese Academy of Sciences, Beijing, 100049, China.
⁵ Department of Physics, Princeton University, Princeton, NJ, 08544, USA.
⁶ Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany.
⁷ National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA.
⁸ Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA.
⁹ Swiss-Norwegian BeamLines at European Synchrotron Radiation Facility, Grenoble, France.
¹⁰ Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal, 20018, San Sebastián, Spain. bernevig@princeton.edu.
¹¹ Department of Physics, Princeton University, Princeton, NJ, 08544, USA. bernevig@princeton.edu.
¹² IKERBASQUE, Basque Foundation for Science, 48013, Bilbao, Spain. bernevig@princeton.edu.
¹³ Donostia International Physics Center (DIPC), Paseo Manuel de Lardizábal, 20018, San Sebastián, Spain. sblanco@dipc.org.
¹⁴ IKERBASQUE, Basque Foundation for Science, 48013, Bilbao, Spain. sblanco@dipc.org.

^# Contributed equally.

Abstract

Geometrically frustrated kagome lattices are raising as novel platforms to engineer correlated topological electron flat bands that are prominent to electronic instabilities. Here, we demonstrate a phonon softening at the k_z = π plane in ScV₆Sn₆. The low energy longitudinal phonon collapses at ~98 K and q = [Formula: see text] due to the electron-phonon interaction, without the emergence of long-range charge order which sets in at a different propagation vector q_CDW = [Formula: see text]. Theoretical calculations corroborate the experimental finding to indicate that the leading instability is located at [Formula: see text] of a rather flat mode. We relate the phonon renormalization to the orbital-resolved susceptibility of the trigonal Sn atoms and explain the approximately flat phonon dispersion. Our data report the first example of the collapse of a kagome bosonic mode and promote the 166 compounds of kagomes as primary candidates to explore correlated flat phonon-topological flat electron physics.