Conflux of tunable Rashba effect and piezoelectricity in flexible magnesium monochalogenide monolayers for next-generation spintronic devices
The coupling of piezoelectric properties to Rashba spin-orbit coupling (SOC) has proven to be the limit breaker that paves the way for the self-powered spintronic device (ACS Nano 2018, 12, 1811-1820). For further advancement in next-generation devices, a new class of buckled, hexagonal magnesium-based chalcogenide monolayers (MgX; X = S, Se, Te) have been predicted which are direct band gap semiconductors satisfying all the stability criteria. The MgTe monolayer shows strong SOC with a Rashba constant of 0.63 eV.Å which is tunable to the extent of ±0.2 eV.Å via biaxial strain. Also, owing to broken inversion symmetry and buckling geometry, MgTe shows a very large in-plane as well as out-of-plane piezoelectric coefficient. These results indicate their prospects for serving as channel semiconducting material in self-powered piezo-spintronic device. Further, a prototype for a digital logic device can be envisioned using ac pulsed technology via a perpendicular electric field. The heat transport is significantly suppressed in these monolayers as observed in their intrinsic low lattice thermal conductivity at room temperature: MgS (9.32 Wm^(-1) K^(-1)), MgSe (4.93 Wm^(-1) K^(-1)) and MgTe (2.02 Wm^(-1) K^(-1)). Further studies indicate that these monolayers can be used as a photocatalytic material for simultaneous production of hydrogen and oxygen on account of having suitable band edge alignment and high charge carrier mobility. This work provides significant theoretical insight into the fundamental and applied properties of these new buckled MgX monolayers, which are highly suitable for futuristic applications at the nanoscale in low-power, self-powered multifunctional electronic and spintronic devices, and solar energy harvesting.