Impurity screening and Friedel oscillations in Floquet-driven two-dimensional metals

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Non-equilibrium Quantum Systems

Background:

• Charged impurities in 2D electron systems are fundamental for understanding material properties.
• Non-equilibrium phenomena in quantum systems are crucial for novel electronic devices.
• Time-periodic driving (Floquet engineering) offers a powerful tool to control material properties.

Purpose of the Study:

• To theoretically investigate the non-equilibrium screening of a charged impurity in a 2D electron system under strong time-periodic driving.
• To analyze how Floquet driving modifies the screened impurity potential and its associated Friedel oscillations.
• To explore the distinct screening behaviors in weak and strong driving regimes.

Main Methods:

• Development of a theoretical framework for non-equilibrium screening.
• Analysis of time-averaged polarization and dielectric functions.
• Investigation of the screened impurity potential and Friedel oscillations under Floquet driving.

Main Results:

• Floquet driving leads to two distinct screening regimes.
• Weak driving induces unconventional Friedel oscillations with multiple spatial periods due to emergent Kohn anomalies.
• Strong driving results in an unscreened impurity potential, suppressing Friedel oscillations.

Conclusions:

• The study reveals a tunable control over Friedel oscillations via Floquet driving.
• The dynamic gating effect of the time-dependent field is responsible for the observed screening modifications.
• This work provides insights into manipulating impurity interactions in driven quantum systems.