Combined tight-binding and configuration interaction study of unfolded electronic structure of G-color center in Si

TL;DR

This study combines tight-binding and configuration interaction methods to analyze the electronic structure of the G-center in silicon, revealing its potential as a source of single and entangled photons for quantum technologies.

Contribution

It introduces a computational approach that integrates tight-binding and unfolding techniques with configuration interaction to study the G-center's electronic properties.

Findings

Small fine-structure splitting of exciton ground state

Potential of G-center as a single and entangled photon emitter

Effective analysis of various configurations using low-cost computation

Abstract

We have theoretically studied the G-center in bulk silicon material using the empirical tight-binding model for calculations of unfolded band structures with configuration interaction correction for the exciton at $\Gamma$ point of the Brillouin zone. The G-center in B configuration (emissive) being a candidate structure as the telecom single- and entangled-photon source has two substitutional carbons and one interstitial atom embedded into the bulk in six equally possible configurations. Taking the advantage of the low computation effort of the tight-binding and unfolding approach, it is possible to calculate and analyze the behavior of a variety of the electronic configurations. Our tight-binding model is able to describe not only the behavior of the G-center in the silicon bulk but using the unfolding approach it can also pinpoint the contributions of different elements of the supercell on the final pseudo-band structure. Moreover, the configuration interaction correction with single-particle basis states computed by our unfolded tight-binding model predicts a very small fine-structure splitting of the ground state exciton both for bright and dark doublet in the studied system. That underscores the possibility of the silicon G-center to become a very good emitter of single and entangled photons for quantum communication and computation applications.