Properties of vibronic excitations of SnV centers in diamond*

Negatively charged tin-vacancy (SnV) defects in diamond hold much potential for quantum communication and modular quantum computation. Almost 40% of the photons emitted by an SnV center are entangled to its spin, and can be used for entangling distant SnV spins. SnV spin qubits can operate at relatively high temperatures of 1-2 K, and are robust to electric fields. However, detailed understanding of many physical aspects of SnV centers is still lacking.

We investigate the interplay between vibronic interactions, spin-orbit coupling, strain and electric and magnetic fields, in both ground and optically excited manifolds of the SnV centers, where all these interactions can be of comparable magnitude. Assuming that the vibronic interactions involve one doubly degenerate phononic mode, we use exact diagonalization to investigate the vibronic states of the SnV centers, and study their spin-optical properties. In particular, we predict new optical absorption and emission lines, their intensity and dependence on light polarization, providing a route to experimental assessment of the theory. We discuss relevance of these results for optical control of the SnV spin, and for spin-photon entanglement in SnV spin qubits.