Strong spin Seebeck effect in Kondo T-shaped double quantum dots

Area of Science:

• Condensed Matter Physics
• Quantum Dots
• Spintronics

Background:

• Investigating thermoelectric and spin thermoelectric properties is crucial for developing advanced quantum devices.
• The Kondo effect in quantum dots influences their electronic transport characteristics.

Purpose of the Study:

• To theoretically investigate the thermoelectric and spin thermoelectric properties of a T-shaped double quantum dot.
• To analyze the impact of temperature, lead spin polarization, and dot level position on these properties within the two-stage Kondo effect regime.

Main Methods:

• Theoretical approach using the numerical renormalization group (NRG) technique.
• Analysis of the (spin) Seebeck coefficient, power factor, and figure of merit.
• Examination of thermal conductance and its relation to the Wiedemann-Franz law.

Main Results:

• The thermal conductance follows a modified Wiedemann-Franz law, even with suppressed Kondo effect stages.
• Spin thermopower is significantly enhanced at temperatures corresponding to the second stage of Kondo screening.
• The spin-thermoelectric response shows high sensitivity to lead spin polarization, with effects observed at ~1% polarization.

Conclusions:

• The interplay between the two-stage Kondo effect and the induced exchange field dictates the spin-thermoelectric response.
• Gate voltage can tune the exchange field, allowing for optimization of spin thermopower.
• This research offers insights into controlling spin-based thermoelectric effects in quantum dot systems.