Spin-charge separation and Kondo effect in an open quantum dot

TL;DR

This paper investigates a quantum dot with nearly perfect conductance, revealing persistent spin quantization despite non-discrete charge, and analyzes the emergence of the Kondo effect at low temperatures.

Contribution

It demonstrates that in an open quantum dot, spin remains quantized while charge does not, and characterizes the Kondo effect in this regime.

Findings

Spin remains quantized as 1/2 or 0 depending on gate voltage.

Kondo effect develops at low temperatures in the doublet state.

Conductance behavior at temperatures below the Kondo temperature.

Abstract

We study a quantum dot connected to the bulk by single-mode junctions at almost perfect conductance. Although the average charge $e\langle N \rangle$ of the dot is not discrete, its spin remains quantized: $s=1/2$ or $s=0$, depending (periodically) on the gate voltage. This drastic difference from the conventional mixed-valence regime stems from the existence of a broad-band, dense spectrum of discrete levels in the dot. In the doublet state, the Kondo effect develops at low temperatures. We find the Kondo temperature $T_K$ and the conductance at $T\lesssim T_K$.