Planar thermal Hall effect from phonons in a Kitaev candidate material.

The thermal Hall effect has emerged as a potential probe of exotic excitations in spin liquids. In the Kitaev magnet -RuCl, the thermal Hall conductivity has been attributed to Majorana fermions, chiral magnons, or phonons. Theoretically, the former two types of heat carriers can generate a "planar" , whereby the magnetic field is parallel to the heat current, but it is unknown whether phonons also could.

Reconciling scaling of the optical conductivity of cuprate superconductors with Planckian resistivity and specific heat.

Materials tuned to a quantum critical point display universal scaling properties as a function of temperature T and frequency ω. A long-standing puzzle regarding cuprate superconductors has been the observed power-law dependence of optical conductivity with an exponent smaller than one, in contrast to T-linear dependence of the resistivity and ω-linear dependence of the optical scattering rate. Here, we present and analyze resistivity and optical conductivity of LaSrCuO with x = 0.