Gate-tunable nonreciprocal response in noncentrosymmetric LaAlO3/SrTiO3 interfaces

Abstract

The electrons confined at the interfacial quantum well of a LaAlO3/SrTiO3(LAO/STO) associated with broken inversion symmetry exhibit various exotic condensed matter phases and rich spin-orbitronic functionalities. This two-dimensional polar conductor may directional propagation of itinerant electrons, i.e. the leftward and rightward currents differ from each other, when the time-reversal symmetry is further broken. This potential rectification effect generally was shown to be very weak due to the fact that kinetic energy is much higher than energies associated with symmetry breakings producing weak perturbation. Here, we show giant gate-tunable nonreciprocal charge transport in the LaAlO3/SrTiO3 conductive oxide interface, where the electrons are confined at two-dimension with low Fermi energy. In addition, the Rashba spin-orbit interaction due to a sub-band hierarchy of this system enables strongly tunable nonreciprocal response through applying a gate voltage. Upon increasing gate voltage, the ratio of resistance change between rightward and leftward currents was increased up to 2.7%. The coefficient  representing the strength of the magnetochiral anisotropy, was measured to be as high as ~ 102 T-1 A-1, which is about three order of magnitude higher than those estimated for typical noncentrosymmetric conductors [1]. Moreover, the magnitude of the directional response exhibits additional higher order magnetic-field dependence. The observed behavior of giant directional response in this system is due to the fact that energies associated with the broken inversion symmetry and the broken time-reversal symmetry are comparable to the Fermi energy, which opens a new route to enhance nonreciprocal responses in polar materials.