  In this study, we report first experimental evidence of spin-momentum locking
in the topological phonons in an inhomogeneously strained Si thin film. The
spin-momentum locking in the topological phonons lead to a longitudinal spin
texture or spatially inhomogeneous spin distribution in the freestanding sample
structure. The spin texture was uncovered using location dependent Hall effect
and planar Hall effect measurement. The charge carrier density and anomalous
Hall resistance showed a linear behavior along the length of the sample.
Similarly, the planar Hall resistance related with the spin dependent
scattering was also found to be different at two different location along the
length of the sample. The spin-momentum locking also gave rise to transverse
thermal spin current and spin-Nernst magneto thermopower response, which was
uncovered using angle dependent longitudinal second harmonic measurement. The
magneto thermopower response was also a function of crystallography of the Si
sample where the sign of the response was opposite for <110> and <100> aligned
samples. The spin-momentum locking in topological phonons may give rise to
large spin dependent response at and above room temperature, which can pave the
way for energy efficient spintronics and spin-caloritronics devices.
