The nematic susceptibility of the ferroquadrupolar metal TmAg2 measured via the elastocaloric effect

• Published in: npj quantum materials Vol. 9; no. 1; pp. 46 - 7
• Main Authors: Rosenberg, Elliott W., Ikeda, Matthias, Fisher, Ian R.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29-05-2024; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/119/2795; 639/766/119/995; Condensed Matter Physics; Curie temperature; Elastic properties; Electrons; Entropy; Jahn-Teller effect; Magnetic fields; Phase transitions; Physics; Physics and Astronomy; Quadrupoles; Quantum Physics; Rare earth elements; Structural Materials; Surfaces and Interfaces; Symmetry; Temperature; Tetragonal lattice; Thin Films
• ISSN: 2397-4648; 2397-4648
• DOI: 10.1038/s41535-024-00658-y

Elastocaloric measurements of the ferroquadrupolar/nematic rare-earth intermetallic TmAg
2
are presented. TmAg
2
undergoes a cooperative Jahn-Teller-like ferroquadrupolar phase transition at 5K, in which the Tm
3+
ion’s local 4
f
electronic ground state doublet spontaneously splits and develops an electric quadrupole moment which breaks the rotational symmetry of the tetragonal lattice. The elastocaloric effect, which is the temperature change in the sample induced by adiabatic strains the sample experiences, is sensitive to quadrupolar fluctuations in the paranematic phase which couple to the induced strain. We show that elastocaloric measurements of this material reveal a Curie-Weiss like nematic susceptibility with a Weiss temperature of T* ≈ 2.7
K
, in agreement with previous elastic constant measurements. Furthermore, we establish that a magnetic field along the c-axis acts as an effective transverse field for the quadrupole moments.