Day / Time
Date(s) - 06/12/2016
13 h 00 min - 14 h 00 min
Ecole de Physique
ICREA-Institucio Catalana de Recerca i Estudis Avançats, Barcelona, Spain
Institut Catala de Nanociencia i Nanotecnologia, CSIC and The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
Bending a dielectric material of any symmetry generates polarization thanks to the so-called flexoelectric effect1. Conversely, applying a voltage to a dielectric material will cause it to bend spontaneously, due to the converse (or inverse) flexoelectric effect. Both direct and inverse flexoelectricity scale strongly with the inverse of the thickness of the material, so that it is at the nanoscale where the most dramatic manifestations of flexoelectricity are found. Some of these will be reviewed in my talk, including unpublished results that show how flexoelectricity allows polarization (an electrical property) to be read without a voltage.
Flexoelectricity, however, is not the only way extract polarization from bending: surface piezoelectricity, arising from the intrinsic asymmetry of interfaces, yields exactly the same functional response to bending as bulk flexoelectricity. In semiconductors, this surface-piezoelectric effect can be very important. As I will show in my talk, the participation of free charge allows semiconductors to generate an orders-of-magnitude bigger flexoelectric-like response than that of dielectric insulators2. What is more, this flexoelectric-like response of semiconductors is completely independent of the crystal thickness and can therefore be important not only at the nanoscale, where conventional (insulator) flexoelectricity is already important, but also at the macroscale.
1P. Zubko, G. Catalan, A. K. Tagantsev, Flexoelectric Effect in Solids, Annual Review of Materials Research 43, 387 (2013)
2J. Narvaez, F. Vasquez, G. Catalan, Enhanced flexoelectric-like response in oxide Semiconductors, Nature 538, 219 (2016).