Abstract
We elucidate a bias-free light-induced orbital and spin current through nonlinear response theory, which generalizes the well-known bulk photovoltaic effect in centrosymmetric broken materials from charge to the spin and orbital degrees of freedom. We use two-dimensional nonmagnetic ferroelectric materials (such as GeS and its analogs) to illustrate this bulk orbital/spin photovoltaic effect, through first-principles calculations. These materials possess a vertical mirror symmetry and time-reversal symmetry but lack of inversion symmetry. We reveal that in addition to the conventional photocurrent that propagates parallel to the mirror plane (under linearly polarized light), the symmetric forbidden photocurrent perpendicular to the mirror actually contains electrons flow, which carries angular momentum information and move oppositely. This generates a pure orbital moment current with zero electric charge current. Such hidden photo-induced pure orbital current could lead to a pure spin current via spin–orbit coupling interactions. Therefore, a four-terminal device can be designed to detect and measure photo-induced charge, orbital, and spin currents simultaneously. All these currents couple with electric polarization P, hence their amplitude and direction can be manipulated through ferroelectric phase transition. Our work provides a route to generalizing nanoscale devices from their photo-induced electronics to orbitronics and spintronics.
Highlights
Bulk photovoltaic (BPV) effect[1], which converts incident alternating optical field into direct electric current in centrosymmetric broken materials, has attracted tremendous attention during the past few decades for its easy manipulation and low energy cost
We show that the spin–orbit coupling (SOC) interaction could convert such orbital degree of freedom (DOF) based bulk orbital photovoltaic (BOPV) current into spin DOF, namely, bulk spin photovoltaic (BSPV) current[33,34,35,36]
The in-plane spin that under glide angular momentum component is suppressed in most k-points of the Brillouin zone (BZ)[30]
Summary
Bulk photovoltaic (BPV) effect[1], which converts incident alternating optical field into direct electric current in centrosymmetric broken materials, has attracted tremendous attention during the past few decades for its easy manipulation and low energy cost. Comparing with conventional light-to-current conversion in a p–n junction between two semiconductors, BPV effect produces electric current everywhere light shines onto the material, which could significantly enhance the conversion efficiency and density. This bias-free approach does not need to deposit electrode contacts to the samples, so that impurities and interface effects can be reduced. The BPV effect uses electron charge degree of freedom (DOF) to generate a biased electric potential in semiconductors[3,4,5,6], which serve as promising electronic devices. Speaking, when the velocities of electrons in the spin up and spin down channels are different (v" À v# ≠ 0), there is a collective motion of electron spin and leads to a nonzero spin current
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
