Giant ratchet magneto-photocurrent in graphene lateral superlattices

Abstract

We report on the observation of the magnetic quantum ratchet effect in graphene with a lateral dual-grating top gate (DGG) superlattice. We show that the THz ratchet current exhibits sign-alternating magneto-oscillations due to the Shubnikov-de Haas effect. The amplitude of these oscillations is greatly enhanced as compared to the ratchet effect at zero magnetic field. The direction of the current is determined by the lateral asymmetry which can be controlled by variation of gate potentials in DGG. We also study the dependence of the ratchet current on the orientation of the terahertz electric field (for linear polarization) and on the radiation helicity (for circular polarization). Notably, in the latter case, switching from right-to left-circularly polarized radiation results in an inversion of the photocurrent direction. We demonstrate that most of our observations can be well fitted by the drift-diffusion approximation based on the Boltzmann kinetic equation with the Landau quantization fully encoded in the oscillations of the density of states.

Beatings of ratchet current magneto-oscillations in GaN-based grating gate structures: Manifestation of spin-orbit band splitting

“…The overall behavior of the observed current, besides beatings, corresponds to that of the magneto-ratchet current most recently detected in CdTe-based quantum wells [74,75] and graphene [77]. Importantly, the oscillations of the magneto-ratchet current are in phase with the SdH oscillations.…”

“…We will show that similar to other structures [74,75,77], the amplitude of the magnetooscillations is greatly enhanced as compared to the ratchet effect at zero magnetic field. We experimentally demonstrate that the photocurrent oscillates in phase with the longitudinal resistance and, therefore, almost follows the SdH oscillations multiplied by a smooth envelope.…”

“…Furthermore, the theoretical consideration of the magnetic ratchet effect in graphene and bi-layer graphene showed that it can be substantially enhanced under the cyclotron resonance (CR) condition [73]. Most recently it has been shown theoretically and observed experimentally that magnetic ratchet effect also can be drastically enhanced by deposition of asymmetric lateral potential introduced by asymmetric periodic metallic structure on top of a structure with two dimensional electron gas [74][75][76][77]. Remarkably, magnetic ratchet strongly increases (by more than two orders of magnitude) in the SdH oscillations regime.…”

Double-Quantum-Well AlGaN/GaN Field Effect Transistors with Top and Back Gates: Electrical and Noise Characteristics

“…The structure included two independent gate structures with different gate lengths, as seen in Figure 3 b. These structures are of special interest for the study of the effects at terahertz frequencies in GaN-based and other material systems (see [ 28 , 29 , 30 , 31 , 32 , 33 ] and references therein).…”

Ratchet effect in frequency-modulated waveguide-coupled emitter arrays

“…Ratchets can be realized in semiconductor, cold atom, superconducting and active matter systems [5]. Application of a static magnetic field broadens this phenomenon allowing introducing magnetic ratchets [6,7]. In finite systems, the ratchet effect consists in the appearance of an inhomogeneous distribution of particle density in space-periodic systems under an action of a time-periodic driving.…”