Confinement-induced berry phase and helicity-dependent photocurrents

Area of Science:

• Condensed Matter Physics
• Quantum Mechanics
• Materials Science

Background:

• Optically active metals exhibit photocurrents sensitive to light helicity.
• This phenomenon is linked to the orbital Berry phase and anomalous velocity at low frequencies.
• Quantum confinement can induce Berry phases in materials lacking intrinsic optical activity.

Purpose of the Study:

• To investigate the Berry-phase contribution to photocurrent in quantum wells made from non-optically active materials.
• To determine how quantum confinement effects influence the Berry phase in such systems.

Main Methods:

• Utilized an envelope approximation method.
• Supported theoretical findings with numerical tight-binding calculations.
• Analyzed the dependence of the Berry-phase contribution on material properties and quantum well geometry.

Main Results:

• The Berry-phase contribution to photocurrent in quantum wells is determined by the intrinsic cubic Berry phase of the bulk material.
• Well width and the direction of the quantum well are critical factors influencing the Berry-phase effect.
• The calculated Berry-phase contribution is significant enough to be potentially observable in existing quantum well experiments.

Conclusions:

• Quantum confinement in non-optically active materials can generate observable Berry-phase-dependent photocurrents.
• The study provides a theoretical framework for understanding and predicting these effects in realistic quantum well structures.
• Experimental verification of these findings is suggested and may have already occurred.