# Graphene resonator as an ultrasound detector for generalized Love waves in a polymer film with two level states

## TL;DR

This study demonstrates the use of graphene resonators to detect generalized Love waves in a polymer film, revealing temperature-dependent elastic properties and dissipation linked to two-level systems at low temperatures.

## Contribution

It introduces a novel application of graphene membranes as ultrasound detectors for surface shear waves and characterizes their temperature-dependent behavior in a polymer-silicon system.

## Key findings

- Surface shear modes identified as generalized Love waves.
- Propagation velocity shows logarithmic temperature dependence below 1 K.
- Dissipation also exhibits a logarithmic temperature dependence.

## Abstract

We have investigated surface shear waves at 22 MHz in a 0.5-micron-thick polymer film on SiO2/Si substrate at low temperatures using suspended and non-suspended graphene as detectors. By tracking ultrasound modes detected by oscillations of a trilayer graphene membrane both in vacuum and in helium superfluid, we assign the resonances to surface shear modes, generalized Love waves, in the resist/silicon-substrate system loaded with gold. The propagation velocity of these shear modes displays a logarithmic temperature dependence below 1 K, which is characteristic for modification of the elastic properties of a disordered solid owing to a large density of two level state (TLS) systems. For the dissipation of the shear mode, we find a striking logarithmic temperature dependence, which indicates a basic relation between the speed of the surface wave propagation and the mode dissipation.