Anisotropic magneto-thermal transport in the frustrated spin ladder BiCu$_{2}$PO$_{6}$

We report the thermal conductivity ($\kappa )$ of $S=$1/2 frustrated two-leg ladder BiCu$_{2}$PO$_{6}$\textbf{. }In this material, an enhanced heat transport along the leg direction (\textbf{b}-axis) is observed above 10 K. This is in good accordance with the previous observation of dispersive, anisotropic magnetic excitation along the reciprocal \textbf{b}-axis [1], which suggests the presence of anisotropic magnetic heat transport along the leg direction. The suppression of the $\kappa (T)$ and its magnetic field dependence are also observed around 15 K which probably leads to the clear double-peak feature in the $\kappa (T)$ at about 6 K and 60 K. Based on the Debye model, this can be interpreted by the resonant scattering between phonon and magnetic energy levels which affects the phonon heat transport.\\[4pt] [1] K. W. Plumb \textit{et al}., Phys. Rev. B \textbf{88}, 024402 (2013).