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Gate-voltage-dependent differential conductance via entangled-state tunneling in quantum point contacts.

Journal of physics. Condensed matter : an Institute of Physics journal·2025

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

¹Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 37673, Republic of Korea.

Journal of Physics. Condensed Matter : an Institute of Physics Journal

|September 23, 2025

Summary

We found a quantum phase transition in quantum point contacts, shifting between symmetric and asymmetric Kondo couplings. This transition, driven by localized spin migration, reveals distinct Kondo temperatures and explains anomalous behaviors.

Keywords:

Kondo effect gate-voltage dependence local density of states quantum phase transition quantum point contacts

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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.