Pushing the Thickness Limit of the Giant Rashba Effect in Ferroelectric Semiconductor GeTe

Area of Science:

• Materials Science
• Condensed Matter Physics
• Quantum Mechanics

Background:

• Ferroelectric Rashba semiconductors (FERSCs) are key for energy-efficient spin-orbitronics.
• Understanding the thickness limits of these effects is crucial for device applications.

Purpose of the Study:

• Investigate the minimum thickness for the Rashba-Spin-Orbit Coupling (SOC) effect in α-GeTe films.
• Explore the underlying mechanisms for the persistence of the Rashba effect at reduced thicknesses.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) to probe electronic band structure.
• First-principles calculations for theoretical analysis of pristine GeTe.
• X-ray photoemission spectroscopy (XPS) to analyze film composition and defects.

Main Results:

• α-GeTe(111) films exhibit a giant Rashba effect down to 1 nm thickness on a Sb-covered Si(111) substrate.
• The Rashba constant remains significant (5.2 ± 0.5 eV·Å) even at 1 nm.
• XPS revealed that interfacial Sb atoms compensate Ge vacancies, preserving the Rashba effect.

Conclusions:

• The giant Rashba effect in α-GeTe is robust and persists down to ultrathin films (1 nm).
• Interfacial engineering with Sb is a viable strategy to maintain spin-orbit coupling effects in FERSCs.
• These findings pave the way for developing next-generation energy-efficient spin-orbitronic devices.