Acoustoelectric effect in two-dimensional Dirac materials exposed to Rayleigh surface acoustic waves

Surface acoustic wave induced transport and strain phenomena in van der Waals materials

“…In contrast to graphene, MoS 2 has strong spin-orbit coupling originating from the d-orbitals of the heavy metal atoms and inversion symmetry breaking in odd layers. MoS 2 promises a rich interaction between spin and valley physics such as a coexistence of valley-Hall and spin-Hall effects [46,[49][50][51][52][53][54][55][56].…”

“…the warping of the electron dispersion in the valleys, and the Berry phase, which Bloch electrons can acquire when traveling in a crystal. When a TMDC monolayer is exposed to a static in-plane electric field and when a current flows in the direction transverse to this electric field, the Berry curvature can lead to a valley Hall effect [55,151]. For an ac electric field, the (first-order) stationary valley Hall current is absent since the time-averaged force acting on electrons vanishes.…”

Surface acoustic wave induced phenomena in two-dimensional materials

“…Over the past decade, many intriguing acoustic-induced effects, including the acousto-electric effect, [81][82][83][84][85][86] acousto-galvanic effect, [86][87][88] acoustic Stark effect, 89,90 acoustic Hall effect and acoustic exciton transport, 91,92 have been experimentally reported by manipulating 2D materials with SAWs. In the meantime, the valley spin-acoustic resonance, 93 valley acousto-electric effect 94,95 and acoustic spin Hall effect 96 were theoretically proposed, awaiting for further experimental verifications.…”

“…The essence of the valley acousto-electric effect lies in the emergence of a drag electric current (and a spin current) and the contribution of the as-generated current was assigned into three parts: one is the conventional diffusion current that is independent of the valley index and proportional to the acoustic wave vector; the other is the Hall-like warping current due to the trigonal warping of electron dispersion; the third is the acousto-electric valley Hall current caused by the Berry phase acquired by Bloch electrons traveling along the 2D crystal. 94,95 In the community of strongly correlated electronic 2D systems, SAWs were attempted to modulate the interplay between charge-density wave (CDW) and superconductivity. In superconducting NbSe 2 thin films on the LiNbO 3 substrate, Yokoi et al 100 reported the SAW-induced negative resistance (a voltage decrease along the opposite direction of the current flow at zero bias) and found that the amplitude of negative resistance increased by elevating the SAW power and lowering the temperature (Fig.…”

“…The essence of the valley acousto-electric effect lies in the emergence of a drag electric current (and a spin current) and the contribution of the as-generated current was assigned into three parts: one is the conventional diffusion current that is independent of the valley index and proportional to the acoustic wave vector; the other is the Hall-like warping current due to the trigonal warping of electron dispersion; the third is the acousto-electric valley Hall current caused by the Berry phase acquired by Bloch electrons traveling along the 2D crystal. 94,95…”