Transmission phase in the Kondo regime revealed in a two-path interferometer

Area of Science:

• Condensed matter physics
• Quantum electronics

Background:

• Understanding quantum phenomena in nanoscale devices is crucial.
• Kondo correlation in quantum dots influences electron transport properties.

Purpose of the Study:

• To directly observe and characterize the transmission phase shift in a Kondo correlated quantum dot.
• To investigate the temperature dependence of the phase shift and its relation to Kondo physics.

Main Methods:

• Utilized a novel two-path interferometer for precise measurements.
• Employed direct observation techniques to monitor transmission phase shifts.
• Performed two-level numerical renormalization group (NRG) calculations for theoretical comparison.

Main Results:

• Observed a distinct π/2 phase shift persisting up to the Kondo temperature (TK).
• Noted a phase shift exceeding π/2 at each Coulomb peak above TK.
• Demonstrated agreement between experimental findings and NRG calculations.

Conclusions:

• The study provides a comprehensive understanding of phase evolution in the Kondo regime of quantum dots.
• Direct observation and theoretical calculations confirm the unique electronic transport characteristics.
• This work elucidates the transition from Kondo behavior to standard Coulomb blockade.