Ultralow-Temperature Heat Transport in Quantum Spin Liquid Candidates: A Brief Review

Heat in solids can be transported by various quasiparticles, making low-temperature heat transport a powerful tool for probing charge-neutral excitations in quantum materials. In recent years, ultralow-temperature heat transport has been instrumental in detecting exotic excitations in quantum spin liquids (QSLs). A non-zero residual thermal conductivity, \kappa_0/T, serves as compelling evidence for the presence of itinerant spinons and the gapless nature of a disordered state. Additionally, the thermal Hall effect (THE) in QSLs can arise from contributions by spinons or Majorana fermions. In this review, we summarize key thermal conductivity findings from various QSL candidates, focusing on the role of spinons in both heat transport and phonon scattering. We also examine different experimental observations and the underlying mechanisms of THE in QSL candidates with three-dimensional pyrochlore structures, as well as two-dimensional honeycomb and triangular lattices. This review offers valuable insights and guidance for understanding ultralow-temperature heat transport in QSLs.