Bulk rectification effect in a polar semiconductor

Abstract

Noncentrosymmetric conductors are an interesting material platform, with rich spintronic functionalities 1,2 and exotic superconducting properties 3,4 typically produced in polar systems with Rashba-type spin-orbit interactions 5 . Polar conductors should also exhibit inherent nonreciprocal transport [6][7][8] , in which the rightward and leftward currents di er from each other. But such a rectification is di cult to achieve in bulk materials because, unlike the translationally asymmetric p-n junctions, bulk materials are translationally symmetric, making this phenomenon highly nontrivial. Here we report a bulk rectification e ect in a three-dimensional Rashba-type polar semiconductor BiTeBr. Experimentally observed nonreciprocal electric signals are quantitatively explained by theoretical calculations based on the Boltzmann equation considering the giant Rashba spin-orbit coupling. The present result o ers a microscopic understanding of the bulk rectification e ect intrinsic to polar conductors as well as a simple electrical means to estimate the spin-orbit parameter in a variety of noncentrosymmetric systems.The effect of the lattice symmetry on the electronic states is a fundamental issue in condensed matter physics. In particular, broken inversion symmetry in the crystal structure generally causes spin band splitting which modifies the electronic ground state, affecting transport properties represented by the superconductivity in noncentrosymmetric systems 3,4 or spin-related transport in nonmagnetic materials 1,2 . Among them, Rashba-5 and Dresselhaus 9 -type spin-orbit interactions are two well-known textbook models which have succeeded in explaining a variety of exotic phenomena in systems without inversion symmetry.Although the Rashba effect has been conventionally studied at surfaces or interfaces [10][11][12][13][14] , the recent discovery of three-dimensional (3D) materials which host a large Rashba-type band splitting [15][16][17][18] pave the way towards exploring novel transport originating from the 3D chiral spin-texture of the electronic band. BiTeX (X = I, Br) is one such bulk polar semiconductor, in which Bi, Te and X layers are stacked alternately so that the mirror symmetry along the c axis is broken (Fig. 1a). The resultant Rashba-type spin splitting of the electronic bands has been confirmed by angle-resolved photoemission spectroscopy (ARPES) 15,16 and the transport signatures of the split Fermi surface have been reported by quantum oscillations in resistance 19 or thermoelectric coefficients 20 . However, characteristic magneto-transport reflecting the spin polarization in the electronic band or polarity of the crystal has been elusive, except for photocurrent experiments on BiTeBr 21 . One of the manifestations of lattice symmetry breaking in electric transport is the rectification effect. In the presence of an in-plane magnetic field, the Rashba-type spin band splitting is modulated to become asymmetric along a direction perpendicular to both the polar axis and the magnetic field (Fig. ...

Observation of the nonlinear Hall effect under time-reversal-symmetric conditions

“…The generalization to gigahertz or terahertz frequencies might be useful for next generation wireless technologies. [38,41,42].…”

Spin-orbit torque and Nernst effect in Bi-Sb/Co heterostructures

“…In addition, it has been reported that the unidirectional spin-Hall magneto-resistance (USMR) is orders of magnitudes larger in topological insulator/ heavy metal bilayers films than in conventional heavy metal/ ferromagnet bilayers [29][30][31][32]. Since the unidirectional magneto-resistance is asymmetric in the current direction as well as the magnetic field direction, harmonic voltage measurements are often used to quantify this phenomenon [33].…”

SOS: symmetry-operational similarity

“…The object can be an electron, a phonon, spin wave, or light in crystalline solids, and the best known example is that of nonreciprocal charge transport (i.e., diode) effects in p-n junctions, where a built-in electric field (E) breaks the directional symmetry [10]. The polarization (P) of ferroelectrics such as BiFeO3 or polar semiconductors such as BiTeBr can also act like the built-in electric field, so bulk diode (and photovoltaic) effects can be realized in these materials [11,12]. Certainly, both E and P are polar vectors, and behave identical under various symmetry operationssimilar with the identical behavior of magnetic field (H) and magnetization (M).…”