Abstract
The product Jahn–Teller effect may occur for such coupled electron–phonon systems in solids where single electrons occupy double degenerate orbitals. We propose that the excited state of the neutral XV split-vacancy complex in diamond, where X and V labels a group-IV impurity atom of X = Si, Ge, Sn, Pb and the vacancy, respectively, is such a system with eg and eu double degenerate orbitals and Eg quasi-localized phonons. We develop and apply ab initio theory to quantify the strength of electron–phonon coupling for neutral XV complexes in diamond, and find a significant impact on the corresponding optical properties of these centers. Our results show good agreement with recent experimental data on the prospective SiV(0) quantum bit, and reveals the complex nature of the excited states of neutral XV color centers in diamond.
Highlights
Fluorescent, paramagnetic point defects in diamond may realize quantum bits for quantum technology
The SiV(−) exhibits short spin coherence times due to phonon dephasing caused by the dynamic Jahn–Teller effect on the orbital doublet,[18] cooling to the millikelvin regime is required for quantum bit operations.[23,24]
We show that the electrons and phonons are strongly coupled in the electronic excited states, and they constitute of a ⊗ Eg product Jahn–Teller system, where eg and eu refers to the corresponding electronic orbitals that are simultaneously coupled to quasi-localized Eg symmetry breaking local vibrational mode
Summary
Fluorescent, paramagnetic point defects in diamond may realize quantum bits for quantum technology. The negatively charged XV, that is, XV(−) defects have S = 1/2 spin state and fluoresce mostly in the visible.[1,2,3,4,5,6,7,8,9,10,11] The inversion symmetry of the centers assumes virtually no Stark shift in the optical signals, which is a prerequisite for realization of indistinguishable single photon sources. SiV(−) is the most studied,[2,4,5,12,13,14,15,16,17,18,19,20,21,22] and stands out with a large Debye–Waller (DW) factor of 0.7, and the demonstration of quantum communication and sensor applications.[12,13] On the other hand, the SiV(−) exhibits short spin coherence times due to phonon dephasing caused by the dynamic Jahn–Teller effect on the orbital doublet,[18] cooling to the millikelvin regime is required for quantum bit operations.[23,24] It is predicted that PbV (−) might have much longer spin coherence times because of the enlarged gap of the orbital doublet caused by spin–orbit interaction, but with the expense of smaller Debye–Waller factor than that of SiV(−).[25]
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