Purity of entangled photon pairs in a semiconductor–superconductor heterostructure in the presence of both Rashba and Dresselhaus SOCs

Abstract

Angular momentum entanglement in the superconducting state as an intrinsic property of superconductors, inducing the polarization-entangled photons, has recently been proposed as a natural source for the generation of entangled photons in P–N–S heterostructures. Breaking the structure inversion symmetry (SIS) and bulk inversion symmetry (BIS) due to Rashba and Dresselhaus spin orbit couplings (SOCs) lead to combination of singlet and triplet superconducting. We provide a general investigation of the effects of Rashba and Dresselhaus SOCs, the contribution of the components of the mixed parity gap function as well as singlet and triplet channels and spatial characteristics of the structure ($\theta$, $\phi$) on the purity of entangled photons. It is shown that the spin singlet pairing plays an important role to enhance the production of entangled pairs, and specifically, in the mixed state, $s+p$ pairing exhibits the highest purity at $\theta =0$ and $\theta =\pi$. For pure singlet pairing the highest purity is obtained from conventional $s$-wave pairing. Furthermore pure triplet pairing exhibits maximum purity of entangled photons at $\phi =0,\pi$ for equal-Rashba–Dresselhaus SOCs case. The results of this article open the window for designing systems including superconductors and semiconductors in order to produce entangled photons.