Surface-State Engineering for Generation of Nonlinear Charge and Spin Photocurrents

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• Nonlinear photocurrents are crucial for optoelectronic devices.
• Spin-orbit interactions in surface states offer unique electronic properties.
• Centrosymmetric materials typically lack net DC photocurrents.

Purpose of the Study:

• To investigate the generation of nonlinear charge and spin photocurrents via spin-orbit split surface states.
• To characterize these photocurrents in centrosymmetric systems like Au(111).
• To identify and evaluate novel material systems for experimental verification.

Main Methods:

• Theoretical modeling combined with density functional calculations.
• Characterization of surface states and their relativistic properties.
• Analysis of nonlinear charge and spin photocurrent generation.

Main Results:

• Demonstrated net DC photocurrent generation in centrosymmetric Au(111) surface states.
• Identified Tl/Si(111) as a promising material with metallic surface states and relativistic properties.
• Observed distinct angular signatures and ferroelectric-like magnitudes for nonlinear charge photocurrents.
• Achieved pure out-of-plane spin-polarized currents from surface states.

Conclusions:

• Surface-state photocurrents hold significant potential for low-bias optoelectronic applications.
• The Tl/Si(111) system offers a versatile platform for nonlinear spin-filtering functionalities.
• This work expands the understanding of nonlinear electronic phenomena in surface states.