@article{61356, abstract = {{First-principles calculations reveal how topological defects in semiconducting carbon nanotubes trap triplet excitons and enable single-photon emission at telecom wavelengths, offering new insights into their potential for photonic devices.}}, author = {{Biktagirov, Timur and Gerstmann, Uwe and Schmidt, Wolf Gero}}, issn = {{2040-3364}}, journal = {{Nanoscale}}, number = {{11}}, pages = {{6884--6891}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{Topological defects in semiconducting carbon nanotubes as triplet exciton traps and single-photon emitters}}}, doi = {{10.1039/d4nr03904a}}, volume = {{17}}, year = {{2025}}, } @article{62926, abstract = {{Abstract Negatively charged boron vacancies () in hexagonal boron nitride (hBN) are emerging as promising solid‐state spin qubits due to their optical accessibility, structural simplicity, and compatibility with photonic platforms. However, quantifying the density of such defects in thin hBN flakes has remained elusive, limiting progress in device integration and reproducibility. Here, an all‐optical method is presented to quantify defect density in hBN by correlating Raman and photoluminescence (PL) signatures with irradiation fluence. Two defect‐induced Raman modes, D1 and D2, are identified and assigned them to vibrational modes of using polarization‐resolved Raman measurements and density functional theory (DFT) calculations. By adapting a numerical model originally developed for graphene, an empirical relationship linking Raman (D1, E 2g ) and PL intensities is established to absolute defect densities. This method is universally applicable across various irradiation types and uniquely suited for thin flakes, where conventional techniques fail. The approach enables accurate, direct, and non‐destructive quantification of spin defect densities down to 10 15  defects/cm 3 , offering a powerful tool for optimizing and benchmarking hBN for quantum optical applications. }}, author = {{Patra, Atanu and Konrad, Paul and Sperlich, Andreas and Biktagirov, Timur and Schmidt, Wolf Gero and Spencer, Lesley and Aharonovich, Igor and Höfling, Sven and Dyakonov, Vladimir}}, issn = {{1616-301X}}, journal = {{Advanced Functional Materials}}, publisher = {{Wiley}}, title = {{{Quantifying Spin Defect Density in hBN via Raman and Photoluminescence Analysis}}}, doi = {{10.1002/adfm.202517851}}, year = {{2025}}, } @article{54853, abstract = {{The nitrogen-vacancy (NV) centers (NCVSi)− in 4H silicon carbide (SiC) constitute an ensemble of spin S = 1 solid state qubits interacting with the surrounding 14N and 29Si nuclei. As quantum applications based on a polarization transfer from the electron spin to the nuclei require the knowledge of the electron–nuclear interaction parameters, we have used high-frequency (94 GHz) electron–nuclear double resonance spectroscopy combined with first-principles density functional theory to investigate the hyperfine and nuclear quadrupole interactions of the basal and axial NV centers. We observed that the four inequivalent NV configurations (hk, kh, hh, and kk) exhibit different electron–nuclear interaction parameters, suggesting that each NV center may act as a separate optically addressable qubit. Finally, we rationalized the observed differences in terms of distinctions in the local atomic structures of the NV configurations. Thus, our results provide the basic knowledge for an extension of quantum protocols involving the 14N nuclear spin.}}, author = {{Murzakhanov, F. F. and Sadovnikova, M. A. and Mamin, G. V. and Nagalyuk, S. S. and von Bardeleben, H. J. and Schmidt, Wolf Gero and Biktagirov, Timur and Gerstmann, Uwe and Soltamov, V. A.}}, issn = {{0021-8979}}, journal = {{Journal of Applied Physics}}, number = {{12}}, publisher = {{AIP Publishing}}, title = {{{14N Hyperfine and nuclear interactions of axial and basal NV centers in 4H-SiC: A high frequency (94 GHz) ENDOR study}}}, doi = {{10.1063/5.0170099}}, volume = {{134}}, year = {{2023}}, } @article{54851, abstract = {{Composites of different graphene oxide types, TiO2 materials, and especially synthetic routes influence the photocatalytic activity of the resulting material.}}, author = {{Rosenthal, Marta and Biktagirov, Timur and Schmidt, Wolf Gero and Wilhelm, René}}, issn = {{2044-4753}}, journal = {{Catalysis Science & Technology}}, number = {{15}}, pages = {{4367--4377}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{Synthesis of new graphene oxide/TiO2 and TiO2/SiO2 nanocomposites and their evaluation as photocatalysts}}}, doi = {{10.1039/d3cy00461a}}, volume = {{13}}, year = {{2023}}, } @article{43827, abstract = {{A series of new organic donor–π–acceptor dyes incorporating a diquat moiety as a novel electron-acceptor unit have been synthesized and characterized. The analytical data were supported by DFT calculations. These dyes were explored in the aerobic thiocyanation of indoles and pyrroles. Here they showed a high photocatalytic activity under visible light, giving isolated yields of up to 97 %. In addition, the photocatalytic activity of standalone diquat and methyl viologen through formation of an electron donor acceptor complex is presented.}}, author = {{Meier, Armin and Badalov, Sabuhi and Biktagirov, Timur and Schmidt, Wolf Gero and Wilhelm, René}}, issn = {{0947-6539}}, journal = {{Chemistry – A European Journal}}, keywords = {{General Chemistry, Catalysis, Organic Chemistry}}, number = {{22}}, pages = {{ e202203541}}, publisher = {{Wiley}}, title = {{{Diquat Based Dyes: A New Class of Photoredox Catalysts and Their Use in Aerobic Thiocyanation}}}, doi = {{10.1002/chem.202203541}}, volume = {{ 29}}, year = {{2023}}, } @article{37713, author = {{Murzakhanov, Fadis F. and Mamin, Georgy Vladimirovich and Orlinskii, Sergei Borisovich and Gerstmann, Uwe and Schmidt, Wolf Gero and Biktagirov, Timur and Aharonovich, Igor and Gottscholl, Andreas and Sperlich, Andreas and Dyakonov, Vladimir and Soltamov, Victor A.}}, issn = {{1530-6984}}, journal = {{Nano Letters}}, keywords = {{Mechanical Engineering, Condensed Matter Physics, General Materials Science, General Chemistry, Bioengineering}}, number = {{7}}, pages = {{2718--2724}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Electron–Nuclear Coherent Coupling and Nuclear Spin Readout through Optically Polarized VB– Spin States in hBN}}}, doi = {{10.1021/acs.nanolett.1c04610}}, volume = {{22}}, year = {{2022}}, } @article{29747, author = {{Jurgen von Bardeleben, Hans and Cantin, Jean-Louis and Gerstmann, Uwe and Schmidt, Wolf Gero and Biktagirov, Timur}}, issn = {{1530-6984}}, journal = {{Nano Letters}}, keywords = {{Mechanical Engineering, Condensed Matter Physics, General Materials Science, General Chemistry, Bioengineering}}, number = {{19}}, pages = {{8119--8125}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Spin Polarization, Electron–Phonon Coupling, and Zero-Phonon Line of the NV Center in 3C-SiC}}}, doi = {{10.1021/acs.nanolett.1c02564}}, volume = {{21}}, year = {{2021}}, } @article{29749, author = {{Murzakhanov, F. F. and Yavkin, B. V. and Mamin, G. V. and Orlinskii, S. B. and von Bardeleben, H. J. and Biktagirov, Timur and Gerstmann, Uwe and Soltamov, V. A.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, pages = {{245203}}, publisher = {{American Physical Society (APS)}}, title = {{{Hyperfine and nuclear quadrupole splitting of the NV− ground state in 4H-SiC}}}, doi = {{10.1103/physrevb.103.245203}}, volume = {{103}}, year = {{2021}}, } @article{19190, abstract = {{Polarons in dielectric crystals play a crucial role for applications in integrated electronics and optoelectronics. In this work, we use density-functional theory and Green's function methods to explore the microscopic structure and spectroscopic signatures of electron polarons in lithium niobate (LiNbO3). Total-energy calculations and the comparison of calculated electron paramagnetic resonance data with available measurements reveal the formation of bound polarons at Nb_Li antisite defects with a quasi-Jahn-Teller distorted, tilted configuration. The defect-formation energies further indicate that (bi)polarons may form not only at Nb_Li antisites but also at structures where the antisite Nb atom moves into a neighboring empty oxygen octahedron. Based on these structure models, and on the calculated charge-transition levels and potential-energy barriers, we propose two mechanisms for the optical and thermal splitting of bipolarons, which provide a natural explanation for the reported two-path recombination of bipolarons. Optical-response calculations based on the Bethe-Salpeter equation, in combination with available experimental data and new measurements of the optical absorption spectrum, further corroborate the geometries proposed here for free and defect-bound (bi)polarons.}}, author = {{Schmidt, Falko and Kozub, Agnieszka L. and Biktagirov, Timur and Eigner, Christof and Silberhorn, Christine and Schindlmayr, Arno and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{2643-1564}}, journal = {{Physical Review Research}}, number = {{4}}, publisher = {{American Physical Society}}, title = {{{Free and defect-bound (bi)polarons in LiNbO3: Atomic structure and spectroscopic signatures from ab initio calculations}}}, doi = {{10.1103/PhysRevResearch.2.043002}}, volume = {{2}}, year = {{2020}}, } @article{17069, author = {{Biktagirov, Timur and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{2643-1564}}, journal = {{Physical Review Research}}, number = {{2}}, title = {{{Spin decontamination for magnetic dipolar coupling calculations: Application to high-spin molecules and solid-state spin qubits}}}, doi = {{10.1103/physrevresearch.2.022024}}, volume = {{2}}, year = {{2020}}, } @article{19194, author = {{Biktagirov, Timur and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{2643-1564}}, journal = {{Physical Review Research}}, title = {{{Spin decontamination for magnetic dipolar coupling calculations: Application to high-spin molecules and solid-state spin qubits}}}, doi = {{10.1103/physrevresearch.2.022024}}, year = {{2020}}, } @article{17070, abstract = {{

EPR spectroscopy reveals the universality class and dynamic effects of the [NH4][Zn(HCOO)3] hybrid formate framework.

}}, author = {{Navickas, Marius and Giriūnas, Laisvydas and Kalendra, Vidmantas and Biktagirov, Timur and Gerstmann, Uwe and Schmidt, Wolf Gero and Mączka, Mirosław and Pöppl, Andreas and Banys, Jūras and Šimėnas, Mantas}}, issn = {{1463-9076}}, journal = {{Physical Chemistry Chemical Physics}}, pages = {{8513--8521}}, title = {{{Electron paramagnetic resonance study of ferroelectric phase transition and dynamic effects in a Mn2+ doped [NH4][Zn(HCOO)3] hybrid formate framework}}}, doi = {{10.1039/d0cp01612h}}, volume = {{22}}, year = {{2020}}, } @article{29745, author = {{Biktagirov, Timur and Gerstmann, Uwe}}, issn = {{2643-1564}}, journal = {{Physical Review Research}}, keywords = {{General Engineering}}, number = {{2}}, publisher = {{American Physical Society (APS)}}, title = {{{Spin-orbit driven electrical manipulation of the zero-field splitting in high-spin centers in solids}}}, doi = {{10.1103/physrevresearch.2.023071}}, volume = {{2}}, year = {{2020}}, } @article{13403, author = {{Biktagirov, Timur and Schmidt, Wolf Gero and Gerstmann, Uwe and Yavkin, Boris and Orlinskii, Sergei and Baranov, Pavel and Dyakonov, Vladimir and Soltamov, Victor}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{19}}, title = {{{Polytypism driven zero-field splitting of silicon vacancies in 6H-SiC}}}, doi = {{10.1103/physrevb.98.195204}}, volume = {{98}}, year = {{2018}}, } @article{13409, author = {{Biktagirov, Timur and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{11}}, title = {{{Calculation of spin-spin zero-field splitting within periodic boundary conditions: Towards all-electron accuracy}}}, doi = {{10.1103/physrevb.97.115135}}, volume = {{97}}, year = {{2018}}, }