Regular and singular Fermi liquid in triple quantum dots: Coherent transport studies

TL;DR

This paper investigates the electron transport properties of a triangular triple quantum dot system with electron-electron interactions, revealing diverse many-electron states and phase transitions between regular and singular Fermi liquids using numerical renormalization group methods.

Contribution

It provides a detailed analysis of the phase diagram of a TQD system, demonstrating how the Fermi liquid phases change with gate potentials and elucidating the conductance behavior via the Friedel sum rule.

Findings

Identification of multiple many-electron regimes with different spin orderings.

Controlled variation of the Luttinger phase affecting conductance.

Qualitative understanding of phase transitions between Fermi liquid states.

Abstract

A system of three coupled quantum dots in a triangular geometry (TQD) with electron-electron interaction and symmetrically coupled to two leads is analyzed with respect to the electron transport by means of the numerical renormalization group. Varying gate potentials this system exhibits extremely rich range of regimes with different many-electron states with various local spin orderings. It is demonstrated how the Luttinger phase changes in a controlled manner which then via the Friedel sum rule formula exactly reproduces the conductance through the TQD system. The analysis of the uncoupled TQD molecule from the leads gives a reliable qualitative understanding of various relevant regimes and gives an insight into the phase diagram with the regular Fermi liquid and singular-Fermi liquid phases.