Quantum Phase Transition and Dynamically Enhanced Symmetry in Quadruple Quantum Dot System

TL;DR

This paper investigates a quadruple quantum dot system revealing a quantum phase transition and a resonance phenomenon, highlighting the interplay of Heisenberg, Kondo, and Ising interactions and the emergence of enhanced symmetry.

Contribution

It introduces a novel quadruple quantum dot setup demonstrating a Kosterlitz-Thouless transition and dynamical symmetry enhancement, advancing understanding of correlated quantum systems.

Findings

Identified a Kosterlitz-Thouless quantum phase transition.

Observed a conductance jump at the transition point.

Linked resonance phenomena to degeneracy and symmetry enhancement.

Abstract

We propose a system of four quantum dots designed to study the competition between three types of interactions: Heisenberg, Kondo and Ising. We find a rich phase diagram containing two sharp features: a quantum phase transition (QPT) between charge-ordered and charge-liquid phases, and a dramatic resonance in the charge liquid visible in the conductance. The QPT is of the Kosterlitz-Thouless type with a discontinuous jump in the conductance at the transition. We connect the resonance phenomenon with the degeneracy of three levels in the isolated quadruple dot and argue that this leads to a Kondo-like dynamical enhancement of symmetry from U(1) x Z_2 to U(1) x U(1).