Phase states of multiterminal mesoscopic normal-metal-superconductor structures

Area of Science:

• Condensed Matter Physics
• Quantum Phenomena
• Mesoscopic Physics

Background:

• Mesoscopic structures with superconducting contacts exhibit complex behaviors.
• Nonequilibrium conditions can induce phase transitions in superconducting systems.
• Magnetoresistance is a key property sensitive to electronic states.

Purpose of the Study:

• To investigate phase transitions in a mesoscopic normal-metal structure with superconducting contacts.
• To analyze the impact of nonequilibrium conditions on the structure's stable states.
• To correlate observed magnetoresistance changes with theoretical models.

Main Methods:

• Fabrication and characterization of a mesoscopic normal-metal structure with four superconducting contacts.
• Inducing nonequilibrium conditions to trigger state transitions.
• Measuring magnetoresistance under varying conditions.
• Applying the quasiclassical Keldysh formalism for theoretical analysis.

Main Results:

• The structure exhibits transitions between three metastable states.
• Different phase configurations are observed under nonequilibrium conditions.
• Spectacular changes in magnetoresistance accompany these transitions.
• Qualitative agreement found between experimental results and theoretical predictions.

Conclusions:

• Nonequilibrium conditions drive significant phase transitions in mesoscopic superconducting structures.
• Observed magnetoresistance changes are directly linked to these phase transitions.
• The quasiclassical Keldysh formalism provides a valid theoretical framework for understanding these phenomena.