Surface acoustic wave generation and detection in the quantum paraelectric regime of SrTiO3-based heterostructures

Abstract

Strontium titanate (STO), apart from being a ubiquitous substrate for complex-oxide heterostructures, possesses a multitude of strongly coupled electronic and mechanical properties. Surface acoustic wave (SAW) generation and detection offers insight into electromechanical couplings that are sensitive to quantum para-electricity and other structural phase transitions. Propagating SAWs can interact with STO-based electronic nanostructures, in particular LaAlO3/SrTiO3 (LAO/STO). Here, we report the generation and detection of SAW within LAO/STO heterointerfaces at cryogenic temperatures (T 2 K) using superconducting interdigitated transducers. The temperature dependence shows an increase in the SAW quality factor that saturates at T & AP; 8 K. The effect of backgate tuning on the SAW resonance frequency shows the possible acoustic coupling with the ferroelastic domain wall evolution. This method of generating SAWs provides a pathway towards the dynamic tuning of ferroelastic domain structures, which are expected to influence the electronic properties of complex-oxide nanostructures. Devices that incorporate SAWs may in turn help to elucidate the role of ferroelastic domain structures in mediating electronic behavior.