Acoustically driven Dirac electrons in monolayer graphene

Abstract

We demonstrate the interaction between surface acoustic waves and Dirac electrons in monolayer graphene at low temperatures and high magnetic fields. A metallic interdigitated transducer launches surface waves that propagate through a conventional piezoelectric GaAs substrate and couple to large-scale monolayer CVD graphene films resting on its surface. Based on the induced acousto-electric current, we characterize the frequency domains of the transducer from its first to the third harmonic. We find an oscillatory attenuation of the SAW velocity depending on the conductivity of the graphene layer. The acoustoelectric current reveals additional fine structure that is absent in pure magneto-transport. In addition we find a shift between the acousto-electric longitudinal voltage and the velocity change of the SAW. We attribute this shift to the periodic strain field from the propagating SAW that slightly modifies the Dirac cone. 1 arXiv:1911.10856v1 [cond-mat.mes-hall]

Acoustically Induced Giant Synthetic Hall Voltages in Graphene

“…The blue line shows the Hall voltage that was measured in the conventional magnetotransport configuration (without SAW) for comparison. We note that while I is constant, I SAW will depend on the magnetic field [21] even for a constant IDT power because the sample conductivity changes when the density of states condenses into Landau levels. By carefully adjusting the IDT power at a constant magnetic field, we are able to completely compensate the conventional Hall voltage by the acoustically induced transverse voltage component.…”

“…Pioneering works have studied the flow of such acoustically induced currents and the buildup of longitudinal voltages under various experimental conditions (temperature, carrier concentration, for different piezoelectric substrates and wiring schemes) [16][17][18][19][20]. Recently, acoustic transport under high magnetic fields and 4.2 Kelvin studied the regime of Landau quantization [21] as many years before in GaAs heterostructures [4,7].…”

Surface acoustic wave induced phenomena in two-dimensional materials

“…The appearance of an additional current and reduced collisional scattering of photo-induced electrons under the piezo-electric field proved the origin of the SAWinduced photo-acoustoelectric effect. 107 In addition, the periodic electric and strain fields of SAWs were also adopted to manifest the graphene Dirac cone 108 and even couple lights into plasmons. 109 In afore-mentioned studies, the majority of 2D materials interplaying with SAWs were mechanically exfoliated from mother crystals and the lateral size was usually limited to below few tens of millimeters.…”

“…The appearance of an additional current and reduced collisional scattering of photo-induced electrons under the piezo-electric field proved the origin of the SAW-induced photo-acoustoelectric effect. 107 In addition, the periodic electric and strain fields of SAWs were also adopted to manifest the graphene Dirac cone 108 and even couple lights into plasmons. 109…”

Giant acoustically-induced synthetic Hall voltages in graphene

“…Pioneering works have studied the flow of such acoustically induced currents and the build-up of longitudinal voltages at 300 K and below 4.2 K in closed-circuit and open-circuit configurations, on different piezoelectric substrates and in dependence of the carrier concentration [16][17][18][19][20] . Recently, acoustic transport under high magnetic fields and 4.2 Kelvin studied the regime of Landau quantization 21 as many years before in GaAs heterostructures 4,7 .…”