Observation of converse flexoelectric effect in topological semimetals

A strong coupling between electric polarization and elastic deformation in solids is an important　factor in creating useful electromechanical nanodevices. Such coupling is typically allowed in insulating materials with inversion symmetry breaking as exemplified by the piezoelectric effect in ferroelectric materials. Therefore, materials with metallicity and centrosymmetry have tended to be out of scope in this perspective. Here, we report the observation of giant elastic deformation by the application of an alternating electric current in topological semimetals (V,Mo)Te2, regardless of the centrosymmetry. Considering the crystal and band structures and the asymmetric measurement configurations in addition to the absence of the electromechanical effect in a trivial semimetal TiTe2, the observed effect is discussed in terms of a Berry-phase-derived converse flexoelectric effect in metals. The observation of the flexoelectric effect in topological semimetals paves a way for a new type of nanoscale electromechanical sensors and energy harvesting. A strong coupling between electric polarization and elastic deformation is important for creating electromechanical nanodevices, but such coupling typically requires inversion symmetry breaking and is elusive in metals. Here, a current-induced giant elastic deformation is reported in topological semimetals VTe2 and MoTe2, regardless of centrosymmetry, due to the Berry phase enhancement of the flexoelectric response.