Josephson transport through a Hubbard impurity center

Area of Science:

• Condensed Matter Physics
• Quantum Mechanics
• Materials Science

Background:

• Josephson transport describes supercurrent flow across a weak link between superconductors.
• Semiconductor barriers with localized magnetic impurities exhibit complex electronic behaviors.
• The on-site Hubbard interaction (U) significantly influences electron correlations in such systems.

Purpose of the Study:

• To investigate the impact of on-site Hubbard interaction (U) on Josephson transport through semiconductor barriers with impurity centers.
• To analyze how the sign and strength of U affect the Josephson current under varying temperatures.
• To explore the conditions leading to current reversals and temporal fluctuations.

Main Methods:

• Theoretical modeling of Josephson transport through a semiconductor barrier.
• Inclusion of impurity centers with arbitrary on-site Hubbard interaction (U).
• Analysis of the system's behavior across different temperature regimes and impurity energy levels.

Main Results:

• For repulsive U, Josephson current sign reversal observed with increasing temperature when impurity level is within (-U,0).
• Strong temporal current fluctuations predicted with few impurity centers present.
• Attractive U at low temperatures simplifies the model to a two-level system, enabling description of non-stationary Josephson effect.

Conclusions:

• The on-site Hubbard interaction critically modifies Josephson transport in semiconductor barriers.
• Temperature-dependent current reversals and fluctuations are key phenomena driven by impurity interactions.
• The study provides a framework for understanding non-stationary Josephson effects in correlated impurity systems.