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

TLDR: In this article, temperature dependent diamagnetic-paramagnetic transitions in thin quantum rings were studied and it was shown 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 and whether or not spin effects are included.

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 ${N}^{\ensuremath{-}1}$ or ${N}^{\ensuremath{-}1/2}$, depending on the presence of spin effects and the value of $N\phantom{\rule{0.16em}{0ex}}\mathrm{mod}\phantom{\rule{0.16em}{0ex}}4$. Analytical results are derived for the susceptibility in the low and high temperature limits, explicitly showing the spin effects on the ring Curie constant.