Surface acoustic wave generation and detection in quantum paraelectric regime of SrTiO$_3$-based heterostructure

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 paraelectricity and other structural phase transitions. Propagating SAWs can interact with STO-based electronic nanostructures, in particular LaAlO3/SrTiO3 (LAO/STO).Here we report generation and detection of SAW within LAO/STO heterointerfaces at cryogenic temperatures (T ≥ 2 K) using superconducting interdigitated transducers (IDTs). The temperature dependence shows an increase in the SAWs quality factor that saturates at T ≈ 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 dynamic tuning of ferroelastic domain structures, which are expected to influence electronic properties of complex-oxide nanostructures. Devices which incorporate SAWs may in turn help to elucidate the role of ferroelastic domain structures in mediating electronic behavior.