Effect of spatial dispersion on acoustoelectric current in a high-mobility two-dimensional electron gas

Acoustically Induced Giant Synthetic Hall Voltages in Graphene

Any departure from graphene's flatness leads to the emergence of artificial gauge fields that act on the motion of the Dirac fermions through an associated pseudomagnetic field. Here, we demonstrate the tunability of strong gauge fields in nonlocal experiments using a large planar graphene sheet that conforms to the deformation of a piezoelectric layer by a surface acoustic wave. The acoustic wave induces a longitudinal and a giant synthetic Hall voltage in the absence of external magnetic fields. The superposition of a synthetic Hall potential and a conventional Hall voltage can annihilate the sample's transverse potential at large external magnetic fields. Surface acoustic waves thus provide a promising and facile avenue for the exploitation of gauge fields in large planar graphene systems.

The photoacoustoelectric effect of the SAW amplification in the structure of Graphene-Piezocrystal LiNbO3

The work presents and analyzes the results of detecting the photoacoustoelectric effect of surface acoustic waves amplification by illumination of a hybrid graphene-LiNbO3 structure. This SAW photoamplification effect is associated with the appearance of an additional photoacoustoelectric current and a decrease of collisional scattering of photoinduced electrons under the action of the SAW electric field. Possible mechanisms of SAW amplification based on the analysis of modern data are discussed. This SAW photoamplification effect can be used to create optoacoustoelectronic devices on a graphene-piezoelectric structures for collecting, amplifying, and detecting superweak sources of THz-radiation photons.

Observation of 990-MHz Optical Oscillation From Light Emitters Excited by High-Order Harmonics of Surface Acoustic Waves

Optomechanical properties have been widely explored on the interactions between phonon, photon, and electrons. The applications range from acoustic filters for mobile handsets to quantum information science./However, up to date, the interaction between harmonic modes of surface acoustic waves (SAWs) and photons has not been studied in detail. Here, we develop radio frequency (RF) - modulated light emitters driven by the coupling between electrical and acoustic signals at room temperature. The light emitter demonstrates a 990-MHz oscillation behavior which cannot be solely achieved by electrical driving due to resistance-capacitance (RC) limit. Instead, the result is attributed to the excitation by the harmonics of SAWs in the light emitter. The ~gigahertz light oscillation enables a new architecture for information processing. In this work, we also demonstrate the coupling between acoustooptical and electrooptical interactions by simultaneously applying 990-MHz acoustic signals and 20-MHz modulated electrical inputs.

Employing graphene acoustoelectric switch by dual surface acoustic wave transducers

We implement a logic switch by using a graphene acoustoelectric transducer at room temperature. We operate two pairs of inter-digital transducers (IDTs) to launch surface acoustic waves (SAWs) on a LiNbO₃ substrate and utilize graphene as a channel material to sustain acoustoelectric current I_ae induced by SAWs. By cooperatively tuning the input power on the IDTs, we can manipulate the propagation direction of I_ae such that the measured I_ae can be deliberately controlled to be positive, negative, or even zero. We define the zero-crossing I_ae as \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${I}_{ae}^{off}$$\end{document}Iaeoff, and then demonstrate that I_ae can be switched with a ratio \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${I}_{ae}^{on}/{I}_{ae}^{off}\, \sim \,{10}^{4}$$\end{document}Iaeon/Iaeoff~104 at a rate up to few tens kHz. Our device with an accessible operation scheme provides a means to convert incoming acoustic waves modulated by digitized data sequence onto electric signals with frequency band suitable for digital audio modulation. Consequently, it could potentially open a route for developing graphene-based logic devices in large-scale integration electronics.

Cyclotron resonance of composite fermions

It is occasionally possible to interpret strongly interacting many-body systems within a single-particle framework by introducing suitable fictitious entities, or 'quasi-particles'. A notable recent example of the successful application of such an approach is for a two-dimensional electron system that is exposed to a strong perpendicular magnetic field. The conduction properties of the system are governed by electron-electron interactions, which cause the fractional quantum Hall effect. Composite fermions, electrons that are dressed with magnetic flux quanta pointing opposite to the applied magnetic field, were identified as apposite quasi-particles that simplify our understanding of the fractional quantum Hall effect. They precess, like electrons, along circular cyclotron orbits, but with a diameter determined by a reduced effective magnetic field. The frequency of their cyclotron motion has hitherto remained enigmatic, as the effective mass is no longer related to the band mass of the original electrons and is entirely generated from electron-electron interactions. Here we demonstrate enhanced absorption of a microwave field in the composite fermion regime, and interpret it as a resonance with the frequency of their circular motion. From this inferred cyclotron resonance, we derive a composite fermion effective mass that varies from 0.7 to 1.2 times that of the electron mass in vacuum as their density is tuned from 0.6 x 10(11) cm(-2) to 1.2 x 10(11) cm(-2).

High-frequency single-electron transport in a quasi-one-dimensional GaAs channel induced by surface acoustic waves

We report on an experimental investigation of the direct current induced by transmitting a surface acoustic wave (SAW) with frequency 2.7 GHz through a quasi-one-dimensional (1D) channel defined in a GaAs - AlGaAs heterostructure by a split gate, when the SAW wavelength was approximately equal to the channel length. At low SAW power levels the current reveals oscillatory behaviour as a function of the gate voltage with maxima between the plateaux of quantized 1D conductance. At high SAW power levels, an acoustoelectric current was observed at gate voltages beyond pinch-off. In this region the current displays a step-like behaviour as a function of the gate voltage (or of the SAW power) with the magnitude corresponding to the transfer of one electron per SAW cycle. We interpret this as due to trapping of electrons in the moving SAW-induced potential minima with the number of electrons in each minimum being controlled by the electron - electron interactions. As the number of electrons is reduced, the classical Coulomb charging energy becomes the Mott - Hubbard gap between two electrons and finally the system becomes a sliding Mott insulator with one electron in each well.