Acoustoelectric drag current in vanadium oxide films

Abstract

Two different Mott insulator wires, vanadium dioxide and vanadium sesquioxide, were prepared on the piezoelectric LiNbO3 substrates. Coupling of acoustic waves propagating in LiNbO3 with free carriers in vanadium oxide gives rise to the acoustoelectric effect that manifests itself as the generation of direct electric current by the acoustic wave. According to a phenomenological model, the value of the effect strongly depends on the wires conductivity, which, for the vanadium-oxide films, changes by a few orders of magnitude. We demonstrated that this yields a significant enhancement of the direct current (DC) current generated in the wires at the metal–insulator transition temperatures. The sign of the generated DC voltage is different for excitations by surface and bulk acoustic wave modes, which may happen due to reverse wave propagation at the substrate surface. For each resonance mode, polarities of the generated DC signal are the same in both wires, despite the signs of charge carriers being different for these materials. It was shown that two complementary techniques (acoustoelectric and Hall effect measurements) yield opposite signs of charge carriers in VO2.

Investigation of Acoustomagnetoelectric Effect in Bandgap Graphene by the Boltzmann Transport Equation

“…is the dielectric function, d ε is the substrate's dielectric constant and 0 ε is the permittivity of free space. The absorption of the SAW's piezoelectric field by the mobile electron in the 2D system is described by Equation (10). Substituting Equation (5)-Equation ( 7) into Equation ( 4), the AME current density is obtained as:…”

“…Since its discovery in the 1950s, the AE effect has been extensively studied in both metals and bulk and low-dimensional semiconductors. The AE effect has been investigated theoretically in carbon nanotubes (CNTs) and superlattices (SLs) [9], as well as experimentally in vanadium oxide films [10]. Other studies have examined the valley AE effect in 2D materials such as a transition metal dichalcogenide monolayer coupled to a piezoelectric substrate [11].…”