Thermal Conductivity of ${\mathrm{Ho}}_2{\mathrm{Ti}}_2{\mathbf{O}}_7$ along the [111] Direction

Thermal transport measurements have been made on the spin-ice material ${\mathrm{Ho}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ in an applied magnetic field with both the heat current and the field parallel to the [111] direction for temperatures from 50 mK to 1.2 K. A large magnetic field $>6\mathrm{T}$ is applied to suppress the magnetic contribution to the thermal conductivity in order to extract the lattice conductivity. The low field thermal conductivity thus reveals a magnetic field dependent contribution to the conductivity which both transfers heat and scatters phonons. We interpret these magnetic excitations as monopolelike excitations and describe their behavior via existing Debye-Hückel theory.