Sequential magnetotunneling in a vertical Quantum Dot tuned at the crossing to higher spin states

TL;DR

This paper investigates the linear magnetoconductance in a vertical quantum dot near the singlet-triplet transition, revealing conductance enhancement and suppression linked to level crossings and spin states, with temperature effects on the conductance features.

Contribution

It provides a detailed calculation of magnetoconductance behavior near the singlet-triplet transition, highlighting the impact of level crossings and spin selection rules.

Findings

Conductance is enhanced before the transition due to level crossings.

A sharp dip in conductance occurs after the transition when the spin state remains unchanged.

Increasing temperature recovers the conductance peak.

Abstract

We have calculated the linear magnetoconductance across a vertical parabolic Quantum Dot with a magnetic field in the direction of the current. Gate voltage and magnetic field are tuned at the degeneracy point between the occupancies N=2 and N=3, close to the Singlet-Triplet transition for N=2. We find that the conductance is enhanced prior to the transition by nearby crossings of the levels of the 3 particle dot. Immediately after it is depressed by roughly 1/3, as long as the total spin S of the 3 electron ground state doesn't change from S=1/2 to S=3/2, due to spin selection rule. At low temperature this dip is very sharp, but the peak is recovered by increasing the temperature.