Three-Dimensional Limit of Bulk Rashba Effect in Ferroelectric Semiconductor GeTe

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Ferroelectric Rashba semiconductors (FERSCs) exhibit a large bulk Rashba parameter (αR), linking spin and electric polarization.
• Integration into microelectronics raises questions about Rashba effect persistence in nanoscale FERSCs.

Purpose of the Study:

• Investigate the persistence and behavior of the Rashba effect in ultrathin ferroelectric materials.
• Determine the thickness limit for the bulk Rashba effect in FERSCs.
• Understand how material thickness influences the Rashba parameter and Berry curvature.

Main Methods:

• Experimental characterization of ultrathin Germanium Telluride (GeTe) films.
• Measurement of the bulk Rashba parameter (αR) as a function of film thickness.
• Analysis of thickness-dependent scaling laws for the Rashba effect.
• Investigation of Berry curvature modifications with changing film thickness.

Main Results:

• A large Rashba parameter (αR = 2.12 eV Å) was observed in a 5.0 nm thick GeTe film.
• A 3D thickness limit (dc = 2.1 ± 0.5 nm) for the bulk Rashba effect was established.
• Thickness was found to modify Berry curvature, impacting polarization and αR.

Conclusions:

• The Rashba effect remains significant in nanometer-scale FERSCs, with GeTe demonstrating robust properties.
• The identified thickness limit provides critical guidance for designing next-generation Rashba-type quantum materials.
• Understanding the interplay between thickness, Berry curvature, and polarization is key for optimizing FERSC performance.