Gate-voltage-driven quantum phase transition at0.7(2e2/h)in quantum point contacts

Area of Science:

• Condensed Matter Physics
• Quantum Information Science

Background:

• Quantum point contacts are crucial for studying electron interactions and quantum phenomena.
• Kondo effect describes the interaction between localized magnetic moments and conduction electrons.

Purpose of the Study:

• Investigate a quantum phase transition in quantum point contacts.
• Analyze the gate-voltage-dependent quasiparticle energy at the Fermi level.
• Understand the relationship between Kondo couplings and localized spin migration.

Main Methods:

• Computed zero-temperature quasiparticle energy from local density of states.
• Utilized replicated gate-voltage-dependent differential conductance line shapes.
• Employed entangled-state tunneling to probe the system.

Main Results:

• Identified a quantum phase transition between symmetric (G⩾0.7G0) and asymmetric (G<0.7G0) Kondo couplings.
• Observed localized spin migration triggered by side-gate voltage.
• Found two distinct Kondo temperatures in the asymmetric phase, one in the symmetric phase.

Conclusions:

• The coexistence of two Kondo temperatures explains anomalous gate-voltage dependence of zero-bias anomaly width.
• The findings clarify the indeterminate Kondo temperature in the asymmetric regime (G<0.7G0).
• This study provides insights into quantum phase transitions and Kondo physics in mesoscopic systems.