Detection of single phonons via phonon drag in two-dimensional materials

Abstract

The capacity to electrically detect phonons, ultimately at the single-phonon limit, is a key requirement for many schemes for phonon-based quantum computing; so-called quantum phononics. Here, we predict that by exploiting the strong coupling of their electrons to surface-polar phonons, van der Waals heterostructures can offer a suitable platform for phonon sensing, capable of resolving energy transfer at the single-phonon level. The geometry we consider is one in which a drag momentum is exerted on electrons in a graphene layer, by a single out-of-equilibrium phonon in a dielectric layer of hexagonal boron nitride, giving rise to a measurable induced voltage $({V}_{\mathrm{drag}})$. Our numerical solution of the Boltzmann transport equation shows that this drag voltage can reach a level of a few hundred microvolts per phonon, well above experimental detection limits. Furthermore, we predict that ${V}_{\mathrm{drag}}$ should be highly insensitive to the mobility of carriers in the graphene layer and to increasing the temperature to at least 300 K, offering the potential of a versatile material platform for single-phonon sensing.