AC Elastocaloric Effect Study of Phase Diagram and Quantum Criticality in α-RuCl3

α-RuCl3 has attracted a great amount of attention as a prime candidate that may host a Kitaev quantum spin liquid state on the honeycomb lattice. A pending question in the field is whether there exists a quantum critical region in proximity to the phase transition from the symmetry breaking zigzag antiferromagnetic phase to the putative field-induced topological quantum spin liquid phase. Leveraging the magnetoelastic coupling of the material, we apply in-plane AC uniaxial strain to study the elastocaloric effect in high-quality α-RuCl3 single crystals. The measurement is of thermodynamic nature and allows us to directly extract the Grüneisen ratio of the system, which is expected to diverge and changes sign near a quantum critical point. We will present the phase diagram mapped out by the elastocaloric effect, along with uniaxial Grüneisen ratio as a function of in-plane magnetic field (parallel or perpendicular to the Ru-Ru bond) and temperature, and discuss the thermodynamic implications for the field-induced quantum phase transitions.