Intersubband optical absorption in InSb stepped quantum wells. Effect of spin sublevels crossing

TL;DR

This paper investigates how spin sublevel crossings in InSb stepped quantum wells under magnetic and electric fields influence intersubband optical absorption, revealing modifications in the spectrum due to these crossings.

Contribution

It introduces an improved Kane model to analyze spin sublevel crossings and their effects on absorption spectra in InSb quantum wells under external fields.

Findings

Discovery of an extra spin level crossing affecting absorption spectra

Absorption spectrum behavior is similar in low and high electron density cases

Modification of optical absorption due to spin sublevel interactions

Abstract

We study linear and non-linear coefficients of the intersubband absorption in InSb-based stepped quantum wells subjected to an in-plane magnetic field. We consider also a transverse electric field to achieve near resonance conditions. Taking into account the two deepest conduction levels and their corresponding Zeeman spin splitting sublevels, we calculate dispersion relations by means of an improved version of Kane model. Besides the known anti-crossing between down and up spin split sublevels, we obtain an extra spin level crossing for some determined parameters. This crossing clearly modifies the absorption spectrum for transitions among the four sublevels considered. We study a low electron density case, when only the first deepest sublevel is occupied, and a high density case with only the highest sublevel empty. We find a similar behavior of the absorption spectrum in both cases.