Speaker
Description
The kagome superconductor CsV$_3$Sb$_5$ ($T_c$ ≈ 2.5 K) hosts a 2×2×2 charge density wave below 94 K$^{[1]}$ and signatures of electronic nematicity and time-reversal-symmetry breaking near 30 K. The interplay of these orders with its superconducting state and Fermi-surface topology remains an open question.
Using resonant torsion magnetometry, we investigate CsV$_3$Sb$_5$ single crystals between 0.7–35 K and 0–14 T. The technique measures the angular curvature of the free energy $k = \partial^2 F/\partial \theta^2$ via resonant-frequency shifts $\Delta f(B,T,\theta)$.
Angular sweeps from out-of-plane to in-plane orientations resolve clear de Haas–van Alphen oscillations superimposed on the uniaxial magnetotropic background. Field sweeps below $T_c$ reveal a pronounced peak inside the superconducting state. The field positions of this peak define a phase boundary $H_1(T)$ internal to the superconducting region, distinct from published $H_{c2}(T)$ curves. At fields above $H_{c2}$, the magnetotropic amplitude exhibits a curvature change near $T$ ≈ 25 K of yet-unestablished origin.
In-plane angular measurements are currently underway to clarify if nematicity is an intrinsic, bulk property of CsV3Sb5, or if there are any additional symmetries broken below 35 K.
In-plane angular measurements at fixed polar angle are currently underway to clarify the microscopic origin of rotational symmetry breaking in this material.
References
[1] Z. Liang et al., Phys. Rev. X 11, 031026 (2021).