  Manipulation of directional magnon propagation, known as magnon spin current,
is essential for developing magnonic memory and logic devices featuring
nonvolatile functionalities and ultralow power consumption. Magnon spin current
can usually be modulated by magnetic field or current-induced spin torques.
However, these approaches may lead to energy dissipation caused by Joule
heating. Electric-field switching of magnon spin current without charge current
is highly desired but very challenging to realize. By integrating magnonic and
piezoelectric materials, we demonstrate manipulation of the magnon spin current
generated by the spin Seebeck effect in the ferrimagnetic insulator Gd3Fe5O12
(GdIG) film on a piezoelectric substrate. We observe reversible electric-field
switching of magnon polarization without applied charge current. Through
strain-mediated magnetoelectric coupling, the electric field induces the
magnetic compensation transition between two magnetic states of the GdIG,
resulting in its magnetization reversal and the simultaneous switching of
magnon spin current. Our work establishes a prototype material platform that
pave the way for developing magnon logic devices characterized by all electric
field reading and writing and reveals the underlying physics principles of
their functions.
