  Ferroic domain walls could play an important role in microelectronics, given
their nanometric size and often distinct functional properties. Until now,
devices and device concepts were mostly based on mobile domain walls in
ferromagnetic and ferroelectric materials. A less explored path is to make use
of polar domain walls in nonpolar ferroelastic materials. Indeed, while the
polar character of ferroelastic domain walls has been demonstrated,
polarization control has been elusive. Here, we report evidence for the
electrostatic signature of the domain-wall polarization in nonpolar calcium
titanate (CaTiO3). Macroscopic mechanical resonances excited by an ac electric
field are observed as a signature of a piezoelectric response caused by polar
walls. On the microscopic scale, the polarization in domain walls modifies the
local surface potential of the sample. Through imaging of surface potential
variations, we show that the potential at the domain wall can be controlled by
electron injection. This could enable devices based on nondestructive
information readout of surface potential.
