Nonlinear Rashba spin splitting in transition metal dichalcogenide monolayers

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Single-layer transition-metal dichalcogenides (TMDs) possess unique electronic band structures suitable for exotic spin-orbital orderings.
• Rashba spin splitting (RSS) is typically linear with external fields or potential gradients in polar materials.

Purpose of the Study:

• Investigate the dependence of RSS in semiconducting TMD monolayers under an applied gate field.
• Explore the potential for novel spintronics applications using gate-tunable spin phenomena.

Main Methods:

• Utilized a gate field to induce and study spin splitting in non-polar TMD monolayers.
• Employed the k·p model combined with symmetry analysis to understand the underlying physics.
• Characterized the anisotropic spin splitting in MoSe₂ under a large gate field.

Main Results:

• Observed an extraordinary nonlinear dependence of RSS in TMD monolayers, unlike linear behavior in polar materials.
• Demonstrated that the potential gradient in non-polar TMDs increases with gate bias, leading to significantly larger nonlinear RSS.
• MoSe₂ exhibited the largest anisotropic spin splitting reported in semiconductors under a large gate field, attributed to third-order contributions.

Conclusions:

• The nonlinear Rashba spin splitting in TMD monolayers is tunable via gate fields.
• This gate-tunable spin splitting in pristine TMD monolayers paves the way for practical spintronics applications.
• Spin-polarized electrons can be generated using external gating in an experimentally accessible manner.