Electron spin relaxation times have been measured in InSb and InAs quantum wells and epi-layers in a moderate (
Nordin MN, Li J, Clowes SK, Curry RJ (2012) Temperature dependent optical properties of PbS nanocrystals., Nanotechnology 23 (27)
A comprehensive study of the optical properties of PbS nanocrystals (NCs) is reported that includes the temperature dependent absorption, photoluminescence (PL) and PL lifetime in the range of 3-300 K. The absorption and PL are found to display different temperature dependent behaviour though both redshift as temperature is reduced. This results in a temperature dependent Stokes shift which increases from
Litvinenko KL, Bowyer ET, Greenland PT, Stavrias N, Li J, Gwilliam R, Villis BJ, Matmon G, Pang ML, Redlich B, van der Meer AF, Pidgeon CR, Aeppli G, Murdin BN (2015) Coherent creation and destruction of orbital wavepackets in Si:P with electrical and optical read-out., Nat Commun 6
The ability to control dynamics of quantum states by optical interference, and subsequent electrical read-out, is crucial for solid state quantum technologies. Ramsey interference has been successfully observed for spins in silicon and nitrogen vacancy centres in diamond, and for orbital motion in InAs quantum dots. Here we demonstrate terahertz optical excitation, manipulation and destruction via Ramsey interference of orbital wavepackets in Si:P with electrical read-out. We show milliradian control over the wavefunction phase for the two-level system formed by the 1s and 2p states. The results have been verified by all-optical echo detection methods, sensitive only to coherent excitations in the sample. The experiments open a route to exploitation of donors in silicon for atom trap physics, with concomitant potential for quantum computing schemes, which rely on orbital superpositions to, for example, gate the magnetic exchange interactions between impurities.
Litvinenko KL, Leontiadou MA, Li J, Bowyer ET, Clowes SK, Pidgeon CR, Murdin BN (2011) Manipulation of spin dynamics in semiconductor structures by orientation of small external magnetic field, AIP Conference Proceedings 1399 pp. 657-658
We have investigated the effect of an external magnetic field on the electron spin lifetime in narrow gap semiconductors (NGS). In zero field, we show that the D'yakonov-Perel process dominates even at low temperatures. In the Faraday configuration it is suppressed and the spin lifetime increases with field, whereas in Voigt configuration, the additional Margulis-Margulis process, which is particularly effective in NGS, shortens the spin lifetime considerably. The spin dynamics are found to be very sensitive to both the magnitude and direction of the magnetic field. © 2011 American Institute of Physics.
Murdin BN, Litvinenko K, Li J, Bowyer E, Pang M, Greenland PT, Villis B, Aeppli G, van der Meer AFG, Redlich B, Engelkamp H, Pidgeon CR (2015) Nano-orbitronics in silicon, Springer Proceedings in Physics 159 pp. 92-93
Nordin MN, Li J, Clowes SK, Curry RJ (2013) Reply to comment on 'Temperature dependent optical properties of PbS nanocrystals', Nanotechnology 24 (28)
Murdin BN, Li J, Pang MLY, Bowyer ET, Litvinenko KL, Clowes SK, Engelkamp H, Pidgeon CR, Galbraith I, Abrosimov NV, Riemann H, Pavlov SG, Huebers H-W, Murdin PG (2013) Si:P as a laboratory analogue for hydrogen on high magnetic field white dwarf stars, NATURE COMMUNICATIONS 4 ARTN 1469
NATURE PUBLISHING GROUP
Bowyer ET, Villis BJ, Li J, Litvinenko KL, Murdin BN, Erfani M, Matmon G, Aeppli G, Ortega JM, Prazeres R, Dong L, Yu X (2014) Picosecond dynamics of a silicon donor based terahertz detector device, Applied Physics Letters 105 (2)
We report the characteristics of a simple complementary metal-oxide-semiconductor compatible terahertz detector device with low response time (nanoseconds) determined using a short-pulse, high intensity free-electron laser. The noise equivalent power was 1 × 10-11 W Hz -1/2. The detector has an enhanced response over narrow bands, most notably at 9.5 THz, with a continuum response at higher frequencies. Using such a device, the dynamics of donors in silicon can be explored, a system which has great potential for quantum information processing. © 2014 AIP Publishing LLC.
We report on the electrical detection of spin dependent photoconductivity in 500 nm wide InSb quantum well nanowires using the optical orientation of electron spins. By applying weak magnetic fields (H 200 mT), we observe a spin filtering effect of classical origin caused by spin dependent back scattering of electrons from the sidewalls. Spin dependent features in the longitudinal photovoltage decay with temperature and disappears at characteristic energy (H 50 K) consistent with the theoretical spin splitting and the thermal level broadening. We show that the observed signal is due to the inversion asymmetry of the quantum well, with an additional Zeeman contribution. © 2012 American Institute of Physics.
To define the mechanism of p47(phox) phosphorylation in regulating endothelial cell response to tumor necrosis factor-± (TNF±) stimulation.
We have measured the near-infrared photoluminescence spectrum of phosphorus doped silicon (Si: P) and extracted the donor-bound exciton (D0X) energy at magnetic fields up to 28 T. At high field the Zeeman effect is strongly nonlinear because of the diamagnetic shift, also known as the quadratic Zeeman effect (QZE). The magnitude of the QZE is determined by the spatial extent of the wave-function. High field data allows us to extract values for the radius of the neutral donor (D0) ground state, and the light and heavy hole D0X states, all with more than an order of magnitude better precision than previous work. Good agreement was found between the experimental state radius and an effective mass model for D0. The D0X results are much more surprising, and the radius of the mJ=±3/2 heavy hole is found to be larger than that of the mJ=±1/2 light hole.
We measure transverse magnetically focused photocurrent signals in an InSb/InAlSb quantum well device. Using optical spin orientation by modulated circularly polarized light an electron spin-dependent signal is observed due to the spin-orbit interaction. Simulations of the focusing signal are performed using a classical billiard ball model, which includes both spin precession and a spin-dependent electron energy. The simulated data suggest that a signal dependent on the helicity of the incident light is expected for a Rashba parameter ± > 0.1 eVÅ and that a splitting of the focusing signal is not expected to be observed in linear polarized photocurrent and purely electrical measurements.
Matmon G, Ginossar E, Villis B, Kolker A, Lim T, Solanki H, Schofield S, Curson N, Li J, Murdin B, Fisher A, Aeppli G (2018) 2D-3D crossover in a dense electron liquid in silicon, Physical Review B 97 155306
American Physical Society
Doping of silicon via phosphine exposures alternating with molecular beam epitaxy overgrowth is a
path to Si:P substrates for conventional microelectronics and quantum information technologies. The
technique also provides a new and well-controlled material for systematic studies of two-dimensional
lattices with a half-filled band. We show here that for a dense (ns = 2.8 × 1014 cm?2
two-dimensional array of P atoms, the full field angle-dependent magnetostransport is remarkably
well described by classic weak localization theory with no corrections due to interaction effects.
The two- to three-dimensional cross-over seen upon warming can also be interpreted using scaling
concepts, developed for anistropic three-dimensional materials, which work remarkably except when
the applied fields are nearly parallel to the conducting planes.
Li Juerong, Le Nguyen H., Litvinenko K., Clowes S. K., Engelkamp H., Pavlov S. G., Hübers H. -W. ., Shuman V. B., Portsel L. M., Lodygin A. N., Astrov A., Abrosimov N. V., Pidgeon C. R., Fisher A., Zeng Zaiping, Niquet Y. -M., Murdin B. N. (2018) Radii of Rydberg states of isolated silicon donors, Physical Review B 98 085423 pp. 085423-1 - 085423-8
American Physical Society
We have performed a high field magneto-absorption spectroscopy on silicon doped with a variety of single and double donor species. The magnetic field provides access to an experimental magnetic length, and the quadratic Zeeman effect in particular may~be used to extract the wavefunction radius without reliance on previously determined effective mass parameters. We were therefore able to determine the limits of validity for the standard one-band anisotropic effective mass model. We also provide improved parameters and use them for an independent check on the accuracy of effective mass theory. Finally, we show that the optically accessible excited state wavefunctions have the attractive property that interactions with neighbours are far more forgiving of position errors than (say) the ground state.
Peach Tomas, Homewood Kevin, Lourenco Manon, Hughes M, Saeedi Kaymar, Stavrias Nikolaos, Li Juerong, Chick Steven, Murdin Benedict, Clowes Steven (2018) The Effect of Lattice Damage and Annealing Conditions on the Hyperfine Structure of Ion Implanted Bismuth Donors in Silicon, Advanced Quantum Technologies 1 (2) 1800038
This study reports on high energy bismuth ion implantation into silicon with a particular emphasis on the effect that annealing conditions have on the observed hyperfine structure of the Si:Bi donor state. A suppression of donor bound exciton, D0X, photoluminescence is observed in implanted samples which have been annealed at 700 °C relating to the presence of a dense layer of lattice defects that is formed during the implantation process. Hall measurments at 10 K show that this implant damage manifests itself at low temperatures as an abundance of p?type charge carriers, the density of which is observed to have a strong dependence on annealing temperature. Using resonant D0X photoconductivity, we are able to identify the presence of a hyperfine structure in samples annealed at a minimum temperature of 800 °C; however, higher temperatures are required to eliminate effects of implantation strain.
We measure transverse magnetically focused photocurrent signals in an InSb/InAlSb quantum well device. Using optical spin orientation by modulated circularly polarized light an electron spin-dependent signal is observed due to the spin-orbit interaction. Simulations of the focusing signal are performed using a classical billiard ball model, which includes both spin precession and a spin-dependent electron energy. The simulated data suggest that a signal dependent on the helicity of the incident light is expected for a Rashba parameter ±0.1eVand that a splitting of the focusing signal is not expected to be observed in linear polarized photocurrent and purely electrical measurements. © 2012 American Physical Society.
This study reports the effect of an increasing ion dose on both the electrical activation yield and the characteristic properties of implanted bismuth donors in silicon. A strong dependence of implant fluence is observed on both the yield of bismuth donors and the measured impurity diffusion. This is such that higher ion concentrations result in both a decrease in activation and an enhancement in donor migration through interactions with mobile silicon lattice vacancies and interstitials. Furthermore, the effect of implant fluence on the properties of the Si:Bi donor bound exciton, D0X, is also explored using photoluminescence (PL) measurements. In the highest density sample, centers corresponding to the PL of bismuth D0Xs within both the high density region and the lower concentration diffused tail of the implanted donor profile are identifiable.