Rashba coupling amplification by a staggered crystal field.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Relativistic effects can create unique electronic states for spintronics.
• Rashba spin-orbit coupling in asymmetric potentials splits electronic bands with opposite spin chirality.
• Achieving significant Rashba splitting typically requires heavy elements or strong electric fields.

Purpose of the Study:

• To investigate the potential for large Rashba coupling in materials lacking heavy elements.
• To explore novel mechanisms for inducing and amplifying spin-orbit coupling.
• To demonstrate effective spin-orbit band engineering in centrosymmetric materials.

Main Methods:

• Angular resolved photoemission spectroscopy (ARPES) was employed to probe electronic states.
• First-principles calculations were utilized to understand the underlying physics.
• Analysis focused on identifying band splitting and spin-chiral polarization.

Main Results:

• Evidence of a large Rashba coupling (0.25 eV Å) in BaNiS2 was found.
• A remarkable band splitting of up to 0.15 eV was observed.
• Hidden spin-chiral polarization was detected, attributed to a large staggered crystal field (1.4 V Å⁻¹) breaking inversion symmetry at the Ni site.

Conclusions:

• A significant Rashba coupling and band splitting were achieved in BaNiS2 without heavy elements.
• A novel mechanism involving a staggered crystal field amplifies Rashba coupling.
• This discovery opens new avenues for spin-orbit band engineering in materials.