Avi Shragai: Phonon Hall viscosity and the thermal Hall effect of RuCl3

Date: Wednesday, May 28th, 2025

Location: Elings Hall, room 1601

Time: 12:30 pm - 1:30 pm

Phonon Hall viscosity and the thermal Hall effect of RuCl3

Abstract: The origin of the thermal Hall effect in RuCl3 remains controversial. In particular, a
sizable phonon contribution complicates the interpretation of a quantized thermal Hall
conductivity. An intriguing possibility is that phonons contribute to the thermal Hall effect
through intrinsic coupling to low-energy spin excitations, acquiring Berry curvature and Hall
viscosity. We use pulse echo ultrasound to measure the Hall viscosity of RuCl3 through its field-induced magnetic phase transition and find nonzero Hall viscosity near the transition, where the thermal Hall conductivity peaks. Our measurement suggests that phonons coupled to spin excitations contribute to the thermal Hall effect in RuCl3.
 

Biography: Before starting his graduate studies, Avi worked in Andrea Young's group at UCSB on the development of a scanning nanoSQUID microscope. After moving to Cornell he worked with Brad Ramshaw using ultrasound to study magnetism and superconductivity.