Dopant Spin in a Semiconductor Adonai R. da Cruz Michael E. Flatté Department of Applied Physics – Photonics and Semiconductor Nanophysics Acknowledgment This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 721394
Dopant Spin in a Semiconductor 2 • Magnetic dopants, NV-centers, SiC divacancies, etc • Suitable for use as spin-qubit • Highly localized electronic states (isolated from decoherence) • Optical transitions (preparation, manipulation, read-out) Point defects in solids as spin-centers • Coupling external electric and magnetic fields • Orbital contribution to the electron magnetic moment through circulating currents Deep-centers from point defects Science 339, 1174 (2013) Coherent control Phys. Rev. Lett. 97, 106803(2006) Science 320, 352–355 (2008)
of the Orbital Magnetic Moment of a Single Dopant Spin in a Semiconductor 3 Orbital magnetization by circulating currents • From the continuity equation for a steady-state (no charge accumulation) circulating currents Phys. Rev. Lett. 112, 187201 (2014). • Current density associated with a wave function
Structure of the Orbital Magnetic Moment of a Single Dopant Spin in a Semiconductor 4 Orbital magnetization by circulating currents • Circulating current for hydrogenic orbitals • Imbalance in mL occupations J. Phys. Chem. Solids, 128, 87-108.
Dopant Spin in a Semiconductor 5 Koster-Slater tight-binding Green’s functions formalism • Point defects in a variety of substrates (III-V, TMDs,etc) • Single magnetic dopant (e.g. Mn, Co, Fe, etc) • Vacancies (e.g. diamond NV-center) • Pair of defects Real-space tight-binding Green’s function Lattice links connecting two atomic sites Empirical tight-binding Hamiltonian in k-space PRL 92, 047201 (2004) PRB 93, 220402(R) (2016) Phys. Rev. B 57, 6493 (1998) Electronic calculation of point defects
Nanoscale Structure of the Orbital Magnetic Moment of a Single Dopant Spin in a Semiconductor 6 Defect potential Density of states (1/ev) Energy (i) (ii) (iii) Electronic calculation of point defects
Single Dopant Spin in a Semiconductor 3d T2 E E E T2 T2 Crystal field Exchange AB-T2 E E B-T2 AB-T2 B-T2 P-d hybridization w/ dangling bonds 113 meV t2 –symmetric acceptor state Spin-polarized Single Mn dopant in GaAs
Dopant Spin in a Semiconductor 11 Spin-correlated circulating current for Mn acceptor state in GaAs 0 0.5 1 1.5 2 2.5 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 1st nearest-neighbors 2nd nearest-neighbors 3rd nearest-neighbors Current operator in tight-binding Green’s function formalism a = 5.65 Å
Structure of the Orbital Magnetic Moment of a Single Dopant Spin in a Semiconductor Theoretical framework to study point-defects and its magnetic properties • Spin-correlated spatial structure of the orbital magnetic moment