Room-temperature electrically switchable spin-valley coupling in a van der Waals ferroelectric halide perovskite with persistent spin helix

Researchers demonstrate a persistent spin helix in an organic-inorganic hybrid ferroelectric halide perovskite whose layered nature makes it intrinsically like a quantum well. They demonstrate a switchable spin-polarized band structure via an intrinsic ferroelectric field. Spintronic devices, by harnessing the spin degree of freedom, are expected to outperform charge-based devices in terms of energy efficiency and speed of operation. The use of an electric field to control spin at room temperature has been pursued for decades. A major hurdle that has contributed to the slow progress in this regard is the dilemma between effective control and strong spin relaxation. For example, in a Rashba/Dresselhaus material with strong spin-orbit coupling, although the internal magnetic field could be substantial enough to effectively control spin precession, often, the spin-relaxation time becomes extremely short as a consequence of Dyakonov-Perel scattering. To address this, a persistent spin helix has been proposed in systems with SU(2) symmetry. Here we show the discovery of the persistent spin helix in an organic-inorganic hybrid ferroelectric halide perovskite whose layered nature makes it intrinsically like a quantum well. We demonstrate that the spin-polarized band structure is switchable at room temperature via an intrinsic ferroelectric field. We reveal valley-spin coupling through a circular photogalvanic effect in single-crystalline bulk crystals. The favoured short spin helix wavelength (three orders of magnitude shorter than in III-V materials), room-temperature operation and non-volatility make the hybrid perovskite an ideal platform for understanding symmetry-tuned spin dynamics, towards designing practical spintronic materials and devices that can resolve the control-relaxation dilemma.

Automated summary

Researchers demonstrate a persistent spin helix in an organic-inorganic hybrid ferroelectric halide perovskite. They show that the spin-polarized band structure can be switched via an intrinsic ferroelectric field. This discovery has the potential to resolve the control-relaxation dilemma in spintronic devices.