Acoustogalvanic Effect in Dirac and Weyl Semimetals

Abstract

A nonlinear mechanism to generate a direct electric current by passing acoustic wave in inversionsymmetric Dirac and Weyl semimetals is proposed. It relies on pseudo-electromagnetic fields originating from dynamical sound-induced strains. Drawing on the similarity with the photogalvanic rectification, where a direct current is produced in a second order response to light, we called this phenomenon the acoustogalvanic effect. Unlike the standard acoustoelectric effect, which relies on the sound-induced deformation potential and the corresponding electric field, the acoustogalvanic one originates from the pseudo-electromagnetic fields, which are not subject to screening. Due to an interplay of the pseudoelectric and pseudomagnetic fields, the acoustogalvanic current shows a nontrivial dependence on the direction of the sound wave propagation. Being within the experimental reach, the effect can be utilized in investigations of the dynamical deformations and provides an effective probe of the pseudo-electromagnetic fields, which are yet to be experimentally observed in Weyl and Dirac semimetals. arXiv:1911.04526v1 [cond-mat.mes-hall]

Topological phonons in oxide perovskites controlled by light

“…In addition, previously unknown phonon-phonon and electron-phonon scattering mechanisms could arise from topological phonons, which may provide new insights into the enhanced superconductivity of SrTiO 3 ( 26 , 59 ). The emergence of Weyl phonons may be accompanied by other unique physical properties such as a pseudogauge field with a one-way propagating bulk mode ( 60 – 62 ), topological negative refraction ( 18 ), and nonlinear acoustic/optical responses ( 63 , 64 ), which can offer new routes for designing novel technologies like light-controlled neuromorphic computing in phononic systems ( 65 , 66 ). Our work shows that oxide perovskites provide a promising platform to explore all of these phenomena and applications.…”

Anomalous acoustoelectric effect induced by clapping modes in chiral superconductors

“…We show that the coupling of the acoustic waves traveling through a chiral superconductor to these modes generates a transverse alternating (ac) current. This is reminiscent of the acoustoelectric effect (AEE), generation of an ac electric current by propagating acoustic waves in metals that was extensively studied since the 1950s [63][64][65][66][67]. Since the transverse current we find is due solely to the chirality of the superconducting order, with no applied magnetic field, we refer to this effect as "anomalous acoustoelectric effect" (AAEE).…”

“…Crystal deformation changes the interatomic length and modifies the hopping integral of normal electrons and the electron energy [63,85]. In the long-wavelength limit (typical wavelength of the sound wave in crystals is 1.0 × 10 −2 cm, much longer than the lattice constants O(1Å)), the effects on the electrons can be described by the effective one-particle deformation potential, v ex (x, t), proportional to the symmetrized strain tensor, u i j = 1 2 (∂ i u j + ∂ j u i ), where u is the displacement vector [67]. The deformation potential induced by the acoustic wave is given by,…”

Dynamical Piezomagnetic Effect in Time-Reversal-Invariant Weyl Semimetals with Axionic Charge-Density Waves

“…By studying the low-energy effective theory of a TR-invariant Weyl-CDW, we find that the phase of the CDW order parameter determines the valley axion field, leading to effective valley axion electrodynamics. Combined with the fact that dynamical strain can act as a pseudo-gauge field in WSMs [52][53][54][55][56][57][58][59][60][61][62][63] , we find that the straininduced pseudo-gauge fields can couple to the electromagnetic field and the valley axion field, resulting in a strain-induced analogue of valley axion electrodynamics: the DPME. The results derived from the low-energy effective theory are further verified against the UV completion by performing a TB calculation.…”