2017, Ezhevskii, A.A., Detochenko, A.P., Soukhorukov, A.V., Guseinov, D.V., Kudrin, A.V., Abrosimov, N.V., Riemann, H.

Spin transport of conduction electrons in silicon samples doped with bismuth in the 1.1•1013 - 7.7•1015 cm-3 concentration range was studied by the Hall effect measurements. The dependence of the Hall voltage magnitude on the magnetic field is the sum of the normal and spin Hall effects. The electrons are partially polarized by an external magnetic field and are scattered by the bismuth spin-orbit potential. Spin-flip scattering results in the additional electromotive force which compensates the normal Hall effect in strong magnetic fields.

2015, Pavlov, S.G., Deßmann, N., Pohl, A., Abrosimov, N.V., Mittendorff, M., Winnerl, S., Zhukavin, R.K, Tsyplenkov, V.V., Shengurov, D.V., Shastin, V.N., Hübers, H.-W.

Ultrafast, ultra-broad-band photoconductive detector based on heavily doped and highly compensated germanium has been demonstrated. Such a material demonstrates optical sensitivity in the more than 8 octaves, in the infrared, from about 2 mm to about 8 μm. The spectral sensitivity peaks up between 2 THz and 2.5 THz and is slowly reduced towards lower and higher frequencies. The life times of free electrons/holes measured by a pump-probe technique approach a few tenths of picoseconds and remain almost independent on the optical input intensity and on the temperature of a detector in the operation range. During operation, a detector is cooled down to liquid helium temperature but has been approved to detect, with a reduced sensitivity, up to liquid nitrogen temperature. The response time is shorter than 200 ps that is significantly faster than previously reported times.

2018, Zhukavin, R.Kh., Kovalevsky, K.A., Tsyplenkov, V.V., Pavlov, S.G., Hübers, H-W., Choporova, Yu.Yu., Knyazev, B.A., Klopf, J.M., Redlich, B., Abrosimov, N.V., Astrov, Yu.A., Shastin, V.N., Silaev, A.A.

This article has no abstract.

2017, Abrosimov, N.V., Aref’ev, D.G., Becker, P., Bettin, H., Bulanov, A.D., Churbanov, M.F., Filimonov, S.V., Gavva, V.A., Godisov, O.N., Gusev, A.V., Kotereva, T.V., Nietzold, D., Peters, M., Potapov, A.M., Pohl, H.-J., Pramann, A., Riemann, H., Scheel, P.-T., Stosch, R., Wundrack, S., Zakel, S.

A metrological challenge is currently underway to replace the present definition of the kilogram. One prerequisite for this is that the Avogadro constant, NA, which defines the number of atoms in a mole, needs to be determined with a relative uncertainty of better than 2  ×  10−8. The method applied in this case is based on the x-ray crystal density experiment using silicon crystals. The first attempt, in which silicon of natural isotopic composition was used, failed. The solution chosen subsequently was the usage of silicon highly enriched in 28Si from Russia. First, this paper reviews previous efforts from the very first beginnings to an international collaboration with the goal of producing a 28Si single crystal with a mass of 5 kg, an enrichment greater than 0.9999 and of sufficient chemical purity. Then the paper describes the activities of a follow-up project, conducted by PTB, to produce a new generation of highly enriched silicon in order to demonstrate the quasi-industrial and reliable production of more than 12 kg of the 28Si material with enrichments of five nines. The intention of this project is also to show the availability of 28Si single crystals as a guarantee for the future realisation of the redefined kilogram.

2017, Rose, B.C., Tyryshkin, A.M., Riemann, H., Abrosimov, N.V., Becker, P., Pohl, H.-J., Thewalt, M.L.W., Itoh, K.M., Lyon, S.A.

We achieve the strong-coupling regime between an ensemble of phosphorus donor spins in a highly enriched 28Si crystal and a 3D dielectric resonator. Spins are polarized beyond Boltzmann equilibrium using spin-selective optical excitation of the no-phonon bound exciton transition resulting in N=3.6×1013 unpaired spins in the ensemble. We observe a normal mode splitting of the spin-ensemble–cavity polariton resonances of 2g√N=580  kHz (where each spin is coupled with strength g) in a cavity with a quality factor of 75 000 (γ≪κ≈60  kHz, where γ and κ are the spin dephasing and cavity loss rates, respectively). The spin ensemble has a long dephasing time (T∗2=9  μs) providing a wide window for viewing the dynamics of the coupled spin-ensemble–cavity system. The free-induction decay shows up to a dozen collapses and revivals revealing a coherent exchange of excitations between the superradiant state of the spin ensemble and the cavity at the rate g√N. The ensemble is found to evolve as a single large pseudospin according to the Tavis-Cummings model due to minimal inhomogeneous broadening and uniform spin-cavity coupling. We demonstrate independent control of the total spin and the initial Z projection of the psuedospin using optical excitation and microwave manipulation, respectively. We vary the microwave excitation power to rotate the pseudospin on the Bloch sphere and observe a long delay in the onset of the superradiant emission as the pseudospin approaches full inversion. This delay is accompanied by an abrupt π-phase shift in the peusdospin microwave emission. The scaling of this delay with the initial angle and the sudden phase shift are explained by the Tavis-Cummings model.

2015, Andrianov, A.V., Zakhar'in, A.O., Zhukavin, R.K., Shastin, V.N., Abrosimov, N.V.

We report on experimental observation and study of terahertz emission from lithium doped silicon crystals under continuous wave band-to-band optical excitation. It is shown that radiative transitions of electrons from 2P excited states of lithium donor to the 1S(A1) donor ground state prevail in the emission spectrum. The terahertz emission occurs due to capture of nonequilibrium electrons to charged donors, which in turn are generated in the crystal as a result of impurity assisted electron-hole recombination. Besides the intracentre radiative transitions the terahertz emission spectrum exhibits also features at about 12.7 and 15.27 meV, which could be related to intraexciton transitions and transitions from the continuum to the free exciton ground state.

2022, Vahapoglu, E., Slack-Smith, J.P., Leon, R.C.C., Lim, W.H., Hudson, F.E., Day, T., Cifuentes, J.D., Tanttu, T., Yang, C. H., Saraiva, A., Abrosimov, N.V., Pohl, H.J., Thewalt, M.L.W., Laucht, A., Dzurak, A.S., Pla, J.J.

Silicon spin qubits promise to leverage the extraordinary progress in silicon nanoelectronic device fabrication over the past half century to deliver large-scale quantum processors. Despite the scalability advantage of using silicon technology, realising a quantum computer with the millions of qubits required to run some of the most demanding quantum algorithms poses several outstanding challenges, including how to control many qubits simultaneously. Recently, compact 3D microwave dielectric resonators were proposed as a way to deliver the magnetic fields for spin qubit control across an entire quantum chip using only a single microwave source. Although spin resonance of individual electrons in the globally applied microwave field was demonstrated, the spins were controlled incoherently. Here we report coherent Rabi oscillations of single electron spin qubits in a planar SiMOS quantum dot device using a global magnetic field generated off-chip. The observation of coherent qubit control driven by a dielectric resonator establishes a credible pathway to achieving large-scale control in a spin-based quantum computer.

2021, Litvinenko, K.L., Le, Nguyen H., Redlich, B., Pidgeon, C.R., Abrosimov, N.V., Andreev, Y., Huang, Zhiming, Murdin, B.N.

The ordinary Fano effect occurs in many-electron atoms and requires an autoionizing state. With such a state, photo-ionization may proceed via pathways that interfere, and the characteristic asymmetric resonance structures appear in the continuum. Here we demonstrate that Fano structure may also be induced without need of auto-ionization, by dressing the continuum with an ordinary bound state in any atom by a coupling laser. Using multi-photon processes gives complete, ultra-fast control over the interference. We show that a line-shape index q near unity (maximum asymmetry) may be produced in hydrogenic silicon donors with a relatively weak beam. Since the Fano lineshape has both constructive and destructive interference, the laser control opens the possibility of state-selective detection with enhancement on one side of resonance and invisibility on the other. We discuss a variety of atomic and molecular spectroscopies, and in the case of silicon donors we provide a calculation for a qubit readout application.

2020, Pavlov, S.G., Deßmann, N., Pohl, A., Zhukavin, R.K., Klaassen, T.O., Abrosimov, N.V., Riemann, H., Redlich, B., Van Der Meer, A.F.G., Ortega, J.-M., Prazeres, R., Orlova, E.E., Muraviev, A.V., Shastin, V.N., Hübers, H.-W.

Transient-type stimulated emission in the terahertz (THz) frequency range has been achieved from phosphorus doped silicon crystals under optical excitation by a few-picosecond-long pulses generated by the infrared free electron lasers FELIX and CLIO. The analysis of the lasing threshold and emission spectra indicates that the stimulated emission occurs due to combined population inversion based lasing and stimulated Raman scattering. Giant gain has been obtained in the optically pumped silicon due to large THz cross sections of intracenter impurity transitions and resonant intracenter electronic scattering. The transient-type emission is formed under conditions when the pump pulse intervals exceed significantly the photon lifetime in the laser resonator. © 2020 Author(s).

2021, Sauter, E., Abrosimov, N.V., Hübner, J., Oestreich, M.

We measure the spin-lattice relaxation of donor bound electrons in ultrapure, isotopically enriched, phosphorus-doped 28Si:P. The optical pump-probe experiments reveal at low temperatures extremely long spin relaxation times which exceed 20 h. The 28Si:P spin relaxation rate increases linearly with temperature in the regime below 1 K and shows a distinct transition to a T9 dependence which dominates the spin relaxation between 2 and 4 K at low magnetic fields. The T7 dependence reported for natural silicon is absent. At high magnetic fields, the spin relaxation is dominated by the magnetic field dependent single phonon spin relaxation process. This process is well documented for natural silicon at finite temperatures but the 28Si:P measurements validate additionally that the bosonic phonon distribution leads at very low temperatures to a deviation from the linear temperature dependence of Γ as predicted by theory.