Temperature dependent diamagnetic-paramagnetic transitions in metal/semiconductor quantum rings

TL;DR

This paper theoretically investigates how temperature influences magnetic susceptibility in metal/semiconductor quantum rings, revealing multiple sign flips and the role of electron count and spin effects.

Contribution

It provides analytical models for temperature-dependent susceptibility in quantum rings, highlighting the impact of electron number and spin on magnetic transitions.

Findings

Susceptibility exhibits multiple sign flips at intermediate and high temperatures.

Sign flip temperature scales inversely with the number of electrons, depending on spin effects.

Analytical expressions show the influence of spin on the ring's Curie constant.

Abstract

We present theoretical studies of temperature dependent diamagnetic-paramagnetic transitions in thin quantum rings. Our studies show that the magnetic susceptibility of metal/semiconductor rings can exhibit multiple sign flips at intermediate and high temperatures depending on the number of conduction electrons in the ring ($N$) and whether or not spin effects are included. When the temperature is increased from absolute zero, the susceptibility begins to flip sign above a characteristic temperature that scales inversely with the number of electrons according to $N^{-1}$ or $N^{-1/2}$, depending on the presence of spin effects and the value of $N\,\mathrm{mod}\,4$. Analytical results are derived for the susceptibility in the low and high temperature limits, explicitly showing the spin effects on the ring Curie constant.