Title: Spin Seebeck effect in a polar antiferromagnet $α$-Cu$_{2}$V$_{2}$O$_{7}$,
Abstract: We have studied the longitudinal spin Seebeck effect in a polar
antiferromagnet $\alpha$-Cu$_{2}$V$_{2}$O$_{7}$ in contact with a Pt film.
Below the antiferromagnetic transition temperature of
$\alpha$-Cu$_{2}$V$_{2}$O$_{7}$, spin Seebeck voltages whose magnetic field
dependence is similar to that reported in antiferromagnetic MnF$_{2}$$\mid$Pt
bilayers are observed. Though a small weak-ferromagnetic moment appears owing
to the Dzyaloshinskii-Moriya interaction in $\alpha$-Cu$_{2}$V$_{2}$O$_{7}$,
the magnetic field dependence of spin Seebeck voltages is found to be
irrelevant to the weak ferromagnetic moments. The dependences of the spin
Seebeck voltages on magnetic fields and temperature are analyzed by a magnon
spin current theory. The numerical calculation of spin Seebeck voltages using
magnetic parameters of $\alpha$-Cu$_{2}$V$_{2}$O$_{7}$ determined by previous
neutron scattering studies reveals that the magnetic-field and temperature
dependences of the spin Seebeck voltages for
$\alpha$-Cu$_{2}$V$_{2}$O$_{7}$$\mid$Pt are governed by the changes in magnon
lifetimes with magnetic fields and temperature.