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  • 1.
    Castelletto, S.
    et al.
    RMIT University, Australia .
    Johnson, B. C.
    University of Melbourne, Australia Japan Atom Energy Agency, Japan .
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Stavrias, N.
    University of Melbourne, Australia .
    Umeda, T.
    University of Tsukuba, Japan .
    Gali, A.
    Hungarian Academic Science, Hungary Budapest University of Technology and Econ, Hungary .
    Ohshima, T.
    Japan Atom Energy Agency, Japan .
    A silicon carbide room-temperature single-photon source2014In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 13, no 2, p. 151-156Article in journal (Refereed)
    Abstract [en]

    Over the past few years, single-photon generation has been realized in numerous systems: single molecules(1), quantum dots(2-4), diamond colour centres5 and others(6). The generation and detection of single photons play a central role in the experimental foundation of quantum mechanics(7) and measurement theory(8). An efficient and high-quality single-photon source is needed to implement quantum key distribution, quantum repeaters and photonic quantum information processing(9). Here we report the identification and formation of ultrabright, room-temperature, photostable single-photon sources in a device-friendly material, silicon carbide (SiC). The source is composed of an intrinsic defect, known as the carbon antisite-vacancy pair, created by carefully optimized electron irradiation and annealing of ultrapure SiC. An extreme brightness (2 x 10(6) counts s(-1)) resulting from polarization rules and a high quantum efficiency is obtained in the bulk without resorting to the use of a cavity or plasmonic structure. This may benefit future integrated quantum photonic devices(9).

  • 2.
    Falk, Abram L.
    et al.
    University of Chicago, IL 60637 USA University of Calif Santa Barbara, CA 93106 USA .
    Klimov, Paul V.
    University of Chicago, IL 60637 USA University of Calif Santa Barbara, CA 93106 USA .
    Buckley, Bob B.
    University of Calif Santa Barbara, CA 93106 USA .
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Calusine, Greg
    University of Calif Santa Barbara, CA 93106 USA .
    Koehl, William F.
    University of Chicago, IL 60637 USA University of Calif Santa Barbara, CA 93106 USA .
    Gali, Adam
    Hungarian Academic Science, Hungary Budapest University of Technology and Econ, Hungary .
    Awschalom, David D.
    University of Chicago, IL 60637 USA University of Calif Santa Barbara, CA 93106 USA .
    Electrically and Mechanically Tunable Electron Spins in Silicon Carbide Color Centers2014In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 112, no 18, p. 187601-Article in journal (Refereed)
    Abstract [en]

    The electron spins of semiconductor defects can have complex interactions with their host, particularly in polar materials like SiC where electrical and mechanical variables are intertwined. By combining pulsed spin resonance with ab initio simulations, we show that spin-spin interactions in 4H-SiC neutral divacancies give rise to spin states with a strong Stark effect, sub-10(-6) strain sensitivity, and highly spin-dependent photoluminescence with intensity contrasts of 15%-36%. These results establish SiC color centers as compelling systems for sensing nanoscale electric and strain fields.

  • 3.
    Falk, Abram L.
    et al.
    University of Chicago, IL 60637 USA; IBM TJ Watson Research Centre, NY 10598 USA.
    Klimov, Paul V.
    University of Chicago, IL 60637 USA; University of Calif Santa Barbara, CA 93106 USA; Hungarian Academic Science, Hungary.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Hungary.
    Szasz, Krisztian
    Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Hungary; Eotvos Lorand University, Hungary.
    Christle, David J.
    University of Chicago, IL 60637 USA; University of Calif Santa Barbara, CA 93106 USA; Hungarian Academic Science, Hungary.
    Koehl, William F.
    University of Chicago, IL 60637 USA.
    Gali, Adam
    Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Hungary; Budapest University of Technology and Econ, Hungary.
    Awschalom, David D.
    University of Chicago, IL 60637 USA.
    Optical Polarization of Nuclear Spins in Silicon Carbide2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 114, no 24, p. 247603-Article in journal (Refereed)
    Abstract [en]

    We demonstrate optically pumped dynamic nuclear polarization of Si-29 nuclear spins that are strongly coupled to paramagnetic color centers in 4H- and 6H-SiC. The 99% +/- 1% degree of polarization that we observe at room temperature corresponds to an effective nuclear temperature of 5 mu K. By combining ab initio theory with the experimental identification of the color centers optically excited states, we quantitatively model how the polarization derives from hyperfine-mediated level anticrossings. These results lay a foundation for SiC-based quantum memories, nuclear gyroscopes, and hyperpolarized probes for magnetic resonance imaging.

  • 4.
    Fashandi, Hossein
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, Hungary.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Katsnelson, Mikhail I.
    Radboud University of Nijmegen, Institute for Molecules and Materials, Nijmegen, The Netherlands / Dept. of Theoretical Physics and Applied Mathematics, Ural Federal University, Russia.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. School of Information and Communication Technology, KTH, Stockholm, Sweden.
    Dirac points with giant spin-orbit splitting in the electronic structure of two-dimensional transition-metal carbides2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 15Article in journal (Refereed)
    Abstract [en]

    We investigated the structural and electrical properties of 2D MXene sheets by means of firstprinciples density functional theory (DFT) calculations. To describe the Kohn-Sham states, plane wave basis set and projector augmented wave method (PAW) were used as implemented in the Vienna ab initio Simulation Package (VASP). We applied PBE parameterization of the generalized gradient approximation of the exchange and correlation energy functional to account for many-body effects of the interacting electron system. Convergent sampling of the Brillouin-zone was achieved by a Γ-centered 15×15×1 grid. In order to model a single sheet of MXene we ensured at least 30 Å vacuum between the periodically repeated sheets. For the structural optimization 1×10−3 eV/Å force criteria was used. The relativistic spin-orbit coupling effects were also included in our simulations regarding band structure and density of states.

  • 5.
    Gueorguiev Ivanov, Ivan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gällström, Andreas
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Leone, Stefano
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kordina, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Tien Son, Nguyen
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Gali, Adam
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Optical properties of the niobium centre in 4H, 6H, and 15R SiC2013In: SILICON CARBIDE AND RELATED MATERIALS 2012, Trans Tech Publications , 2013, Vol. 740-742, p. 405-408Conference paper (Refereed)
    Abstract [en]

    A set of lines in the photoluminescence spectra of 4H-, 6H-, and 15R-SiC in the near-infrared are attributed to Nb-related defects on the ground of doping experiments conducted with 4H-SiC. A model based on a an exciton bound at the Nb-centre in an asymmetric split vacancy configuration at a hexagonal site is proposed, which explains the structure of the luminescence spectrum and the observed Zeeman splitting of the lines.

  • 6.
    Gällström, Andreas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Leone, Stefano
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Kordina, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Son, Nguyen Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Wigner Research Center for Physics, Hungarian Academy of Sciences, Hungary.
    Gali, Adam
    Wigner Research Center for Physics, Hungarian Academy of Sciences, Budapest Hungary; Department of Atomic Physics, Budapest University of Technology and Economics, Budapest, Hungary.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Materials Modeling and Development Laboratory, NUST “MISIS,” Moscow, Russia; LACOMAS Laboratory, Tomsk State University, Tomsk, Russia.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivanov, Ivan G.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Optical properties and Zeeman spectroscopy of niobium in silicon carbide2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 7, p. 1-14, article id 075207Article in journal (Refereed)
    Abstract [en]

    The optical signature of niobium in the low-temperature photoluminescence spectra of three common polytypes of SiC (4H, 6H, and 15R) is observed and confirms the previously suggested concept that Nb occupies preferably the Si-C divacancy with both Si and C at hexagonal sites. Using this concept we propose a model considering a Nb-bound exciton, the recombination of which is responsible for the observed luminescence. The exciton energy is estimated using first-principles calculation and the result is in very good agreement with the experimentally observed photon energy in 4H SiC at low temperature. The appearance of six Nb-related lines in the spectra of the hexagonal 4H and 6H polytypes at higher temperatures is tentatively explained on the grounds of the proposed model and the concept that the Nb center can exist in both C1h and C3v symmetries. The Zeeman splitting of the photoluminescence lines is also recorded in two different experimental geometries and the results are compared with theory based on phenomenological Hamiltonians. Our results show that Nb occupying the divacancy at the hexagonal site in the studied SiC polytypes behaves like a deep acceptor.

  • 7.
    Ivády, Viktor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gali, A
    Hungarian Academic Science, Hungary.
    Role of screening in the density functional applied to transition-metal defects in semiconductors2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 20Article in journal (Refereed)
    Abstract [en]

    We study selected transition-metal-related point defects in silicon and silicon carbide semiconductors by a range-separated hybrid density functional (HSE06). We find that HSE06 does not fulfill the generalized Koopmans' theorem for every defect, which is due to the self-interaction error in the functional in such cases. Restoring the so-called generalized Koopmans' condition with a simple correction in the functional can eliminate this error and brings the calculated charge transition levels remarkably close to the experimental data as well as to the calculated quasiparticle levels from many-body perturbation theory.

  • 8.
    Ivády, Viktor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gali, Adam
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Theoretical investigation of the single photon emitter carbon antisite-vacancy pair in 4H-SiC2014In: SILICON CARBIDE AND RELATED MATERIALS 2013, PTS 1 AND 2, Trans Tech Publications , 2014, Vol. 778-780, p. 495-498Conference paper (Refereed)
    Abstract [en]

    Well addressable and controllable point defects in device friendly semiconductors are desired for quantum computational and quantum informational processes. Recently, such defect, an ultra-bright single photon emitter, the carbon antisite - vacancy pair, was experimentally investigated in 4H-SiC. In our theoretical work, based on ab initio calculation and group theory analysis, we provide a deeper understanding of the features of the electronic structures and the luminescence process of this defect.

  • 9.
    Ivády, Viktor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Armiento, Rickard
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Szasz, Krisztian
    Hungarian Academic Science, Hungary Eotvos Lorand University, Hungary .
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gali, Adam
    Hungarian Academic Science, Hungary Budapest University of Technology and Econ, Hungary .
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Theoretical unification of hybrid-DFT and DFT plus U methods for the treatment of localized orbitals2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 3, p. 035146-Article in journal (Refereed)
    Abstract [en]

    Hybrid functionals serve as a powerful practical tool in different fields of computational physics and quantum chemistry. On the other hand, their applicability for the case of correlated d and f orbitals is still questionable and needs more considerations. In this article we formulate the on-site occupation dependent exchange correlation energy and effective potential of hybrid functionals for localized states and connect them to the on-site correction term of the DFT+ U method. The resultant formula indicates that the screening of the onsite electron repulsion is governed by the ratio of the exact exchange in hybrid functionals. Our derivation provides a theoretical justification for adding a DFT+ U-like on-site potential in hybrid-DFT calculations to resolve issues caused by overscreening of localized states. The resulting scheme, hybrid DFT+ V-w, is tested for chromium impurity in wurtzite AlN and vanadium impurity in 4H-SiC, which are paradigm examples of systems with different degrees of localization between host and impurity orbitals.

  • 10.
    Ivády, Viktor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. Hungarian Academic Science, Hungary.
    Simon, Tamas
    Budapest University of Technology and Econ, Hungary.
    Maze, Jeronimo R.
    Pontificia University of Catolica Chile, Chile.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. National University of Science and Technology MISIS, Russia; Tomsk State University, Russia.
    Gali, Adam
    Hungarian Academic Science, Hungary; Budapest University of Technology and Econ, Hungary.
    Pressure and temperature dependence of the zero-field splitting in the ground state of NV centers in diamond: A first-principles study2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 23, p. 235205-Article in journal (Refereed)
    Abstract [en]

    Nitrogen-vacancy centers in diamond (NV) attract great attention because they serve as a tool in many important applications. The NV center has a polarizable spin S = 1 ground state and its spin state can be addressed by optically detected magnetic resonance (ODMR) techniques. The m(S) = 0 and m(S) = +/- 1 spin levels of the ground state are separated by about 2.88 GHz in the absence of an external magnetic field or any other perturbations. This zero-field splitting (ZFS) can be probed by ODMR. As this splitting changes as a function of pressure and temperature, the NV center might be employed as a sensor operating at the nanoscale. Therefore, it is of high importance to understand the intricate details of the pressure and temperature dependence of this splitting. Here we present an ab initio theory of the ZFS of the NV center as a function of external pressure and temperature including detailed analysis on the contributions of macroscopic and microscopic effects. We found that the pressure dependence is governed by the change in the distance between spins as a consequence of the global compression and the additional local structural relaxation. The local structural relaxation contributes to the change of ZFS with the same magnitude as the global compression. In the case of temperature dependence of ZFS, we investigated the effect of macroscopic thermal expansion as well as the consequent change of the microscopic equilibrium positions. We could conclude that theses effects are responsible for about 15% of the observed decrease of ZFS.

  • 11.
    Ivády, Viktor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Hungarian Academic Science, Hungary.
    Szasz, Krisztian
    Hungarian Academic Science, Hungary.
    Falk, Abram L.
    University of Chicago, IL 60637 USA; IBM Corp, NY 10598 USA.
    Klimov, Paul V.
    University of Chicago, IL 60637 USA; University of Calif Santa Barbara, CA 93106 USA.
    Christle, David J.
    University of Chicago, IL 60637 USA; University of Calif Santa Barbara, CA 93106 USA.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. National University of Science and Technology MISIS, Russia; Tomsk State University, Russia.
    Awschalom, David D.
    University of Chicago, IL 60637 USA.
    Gali, Adam
    Hungarian Academic Science, Hungary; Budapest University of Technology and Econ, Hungary.
    Theoretical model of dynamic spin polarization of nuclei coupled to paramagnetic point defects in diamond and silicon carbide2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 11, p. 115206-Article in journal (Refereed)
    Abstract [en]

    Dynamic nuclear spin polarization (DNP) mediated by paramagnetic point defects in semiconductors is a key resource for both initializing nuclear quantum memories and producing nuclear hyperpolarization. DNP is therefore an important process in the field of quantum-information processing, sensitivity-enhanced nuclear magnetic resonance, and nuclear-spin-based spintronics. DNP based on optical pumping of point defects has been demonstrated by using the electron spin of nitrogen-vacancy (NV) center in diamond, and more recently, by using divacancy and related defect spins in hexagonal silicon carbide (SiC). Here, we describe a general model for these optical DNP processes that allows the effects of many microscopic processes to be integrated. Applying this theory, we gain a deeper insight into dynamic nuclear spin polarization and the physics of diamond and SiC defects. Our results are in good agreement with experimental observations and provide a detailed and unified understanding. In particular, our findings show that the defect electron spin coherence times and excited state lifetimes are crucial factors in the entire DNP process.

  • 12.
    Szasz, K.
    et al.
    Institute for Solid State Physics and Optics, Wigner Research Centre for Physics of the Hungarian Academy of Sciences, Hungary, Institute of Physics, Loránd Eötvös University, Hungary.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. Institute for Solid State Physics and Optics, Wigner Research Centre for Physics of the Hungarian Academy of Sciences, Hungary .
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gali, A.
    Institute for Solid State Physics and Optics, Wigner Research Centre for Physics of the Hungarian Academy of Sciences, Hungary, Department of Atomic Physics, Budapest University of of Technology and Economics, Hungary.
    First principles investigation of divacancy in SiC polytypes for solid state qubit application2014In: SILICON CARBIDE AND RELATED MATERIALS 2013, PTS 1 AND 2, Stafa-Zurich, Switzerland: Trans Tech Publications , 2014, Vol. 778-780, p. 499-502Conference paper (Refereed)
    Abstract [en]

    We calculated the hyperfine structure and the zero-field splitting parameters of divacancies in 3C, 4H and 6H SiC in the ground state and in the excited state for 4H SiC within the framework of density functional theory. Besides that our calculations provide identification of the defect in different polytypes, we can find some carbon atoms next to the divacancy that of the spin polarizations are similar in the ground and excited states. This coherent nuclear spin polarization phenomenon can be the base to utilize 13C spins as quantum memory.

  • 13.
    Szasz, Krisztian
    et al.
    Hungarian Academic Science, Hungary; Eotvos Lorand University, Hungary.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. Hungarian Academic Science, Hungary.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. National University of Science and Technology MISIS, Russia; Tomsk State University, Russia.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bockstedte, Michel
    University of Erlangen Nurnberg, Germany; Salzburg University, Austria; University of Basque Country, Spain.
    Gali, Adam
    Hungarian Academic Science, Hungary; Budapest University of Technology and Econ, Hungary.
    Spin and photophysics of carbon-antisite vacancy defect in 4H silicon carbide: A potential quantum bit2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 12, p. 121201-Article in journal (Refereed)
    Abstract [en]

    Silicon carbide with engineered point defects is considered as very promising material for the next generation devices, with applications ranging from electronics and photonics to quantum computing. In this context, we investigate the spin physics of the carbon antisite-vacancy pair that in its positive charge state enables a single photon source. We find by hybrid density functional theory and many-body perturbation theory that the neutral defect possesses a high spin ground state in 4H silicon carbide and provide spin-resonance signatures for its experimental identification. Our results indicate the possibility for the coherent manipulation of the electron spin by optical excitation of this defect at telecom wavelengths, and suggest the defect as a candidate for an alternative solid state quantum bit.

  • 14.
    Trinh, Xuan Thang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology. Hungarian Academy of Sciences, Budapest, Hungary.
    Kawahara, Koutarou
    Department of Electronic Science and Engineering, Kyoto University, Japan.
    Suda, Jun
    Department of Electronic Science and Engineering, Kyoto University, Japan.
    Kimoto, Tsunenobu
    Department of Electronic Science and Engineering, Kyoto University, Japan.
    Gali, Ádam
    Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Hungary / Department of Atomic Physics, Budapest University of Technology and Economics, Hungary.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Son, Nguyen Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Electron paramagnetic resonance studies of carbon interstitial related defects in 4H-SiC2015Manuscript (preprint) (Other academic)
    Abstract [en]

    In n-type 4H-SiC grown by chemical vapor deposition and irradiated by low-energy (250 keV) electrons, an electron paramagnetic resonance center, labeled EI8a, was observed at room temperature. A short anneal at temperatures in the range of 300-500 °C in darkness changes EI8a to a new center, labeled EI8b, which can be converted back by illumination at room temperature. We show that EI8a and EI8b are the two different configurations of the same defect, labeled EI8, with C1h symmetry and an electron spin S=1/2. The EI8 center is stable up to ~650 °C and annealed out at ~800 °C. Based on the observed hyperfine structures due to the hyperfine interaction between the electron spin and the nuclear spins of four 29Si atoms and three 13C atoms, the EI8 center is suggested to be related to a carbon interstitial cluster.

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