Transition Temperature of a Magnetic Semiconductor with Angular Momentum j

TL;DR

This study uses dynamical mean-field theory to determine the optimal conditions for high transition temperatures in magnetic semiconductors, highlighting the importance of band angular momentum and effective mass ratios.

Contribution

It reveals that maximum Tc occurs at angular momentum j=3/2 with equal band masses, guiding future material design for higher Tc in dilute magnetic semiconductors.

Findings

Maximum Tc at j=3/2 and equal masses

Tc decreases as mass ratio deviates from one

Strategies for optimizing Tc include strain engineering and band structure tuning

Abstract

We employ dynamical mean-field theory to identify the materials properties that optimize Tc for a generalized double-exchange (DE) model. We reach the surprising conclusion that Tc achieves a maximum when the band angular momentum j equals 3/2 and when the masses in the 1/2 and 3/2 sub-bands are equal. However, we also find that Tc is significantly reduced as the ratio of the masses decreases from one. Consequently, the search for dilute magnetic semiconductors (DMS) materials with high Tc should proceed on two fronts. In semiconductors with p bands, such as the currently studied Mn-doped Ge and GaAs semiconductors, Tc may be optimized by tuning the band masses through strain engineering or artificial nanostructures. On the other hand, semiconductors with s or d bands with nearly equal effective masses might prove to have higher Tc's than p-band materials with disparate effective masses.