ICT2014 Abstracts

Phonons carry sound and heat but in no textbook are they associated with magnetism.  Yet here we show experimentally that acoustic phonons in InSb are sensitive to the presence of an external magnetic field: the lattice thermal conductivity in that solid is decreased in the presence of a 7 T field by 12% at 7K.  We attribute this to a local phonon-induced diamagnetic moment in the solid arising from the effect of atomic displacements on conduction and valence band electrons.  The spatial and temporal averages of these phonon-induced magnetic moments are of course zero.  The local magnetic moments have strong spatial gradients which, in the presence of an external field, exert a local magnetic force on the atoms.  This magnetic force adds to the interatomic forces between the atoms in the solid, making them more anharmonic, which in turn promotes phonon-phonon interactions that limit the thermal conductivity.