Direct observation of the donor nuclear spin in a near-gap bound exciton transition: P31 in highly enriched S28i

Abstract

Observation of an electrically tunable exciton g factor in InGaAs/GaAs quantum dots Appl. Phys. Lett. 96, 053113 (2010); 10.1063/1.3309684 Indirect transitions, free and impurity-bound excitons in gallium phosphide: A revisit with modulation and photoluminescence spectroscopyWe report on ultrahigh resolution studies of the bound exciton states associated with the shallow acceptor B and the shallow donor P in highly enriched 28 Si using a tuneable single frequency laser to perform photoluminescence excitation spectroscopy. The linewidths and fine structure of the transitions, which were too narrow to be resolved previously using an available photoluminescence apparatus, are now fully revealed. The P bound exciton transition shows a complicated additional structure, which the Zeeman spectroscopy demonstrates to be a result of the splitting of the donor ground state by the hyperfine interaction between the spin of the donor electron and that of the 31 P nucleus. The 31 P nuclear spin populations can thus be determined, and hopefully modified, by optical means. The predominant Auger recombination channel of these bound excitons is used to observe the same resolved hyperfine transitions in the photocurrent spectrum. This demonstrates that donors in specific electronic and nuclear spin configurations can be selectively photoionized. Possible applications of these results to quantum computing and quantum information systems are discussed.

Isotope engineering of silicon and diamond for quantum computing and sensing applications

“…3). [71][72][73] Furthermore, introducing one more laser irradiation at one of the phosphorus PLE peak frequencies, corresponding to the 31 P nuclear spin up or down, led to extremely fast (~0.1 s) electron and nuclear polarizations of 90 and 76%, respectively. [74] This fast initialization and nuclear spin readout technique was employed to demonstrate the long 31 P nuclear coherence times reported in Refs.…”

Silicon as a model ion trap: Time domain measurements of donor Rydberg states

“…The Bohr model is equally applicable to donor impurity atoms in semiconductor physics, where the conduction band corresponds to the vacuum, and the loosely bound electron orbiting a singly charged core has a hydrogen-like spectrum according to the usual Bohr-Sommerfeld formula, shifted to the far-infrared because of the small effective mass and high dielectric constant. As with atoms in traps the ground states are tightly confined and well isolated from the environment, giving rise to extraordinarily sharp transitions (3)(4)(5) and very long spin coherence times (6,7), measured with magnetic resonance experiments. There are several proposals for quantum information processing based on the spin of silicon donors (8)(9)(10)(11)(12)(13) and such impurities can now be placed singly with atomic precision (14).…”

“…For a real material, however, determination of relaxation times from the frequency domain linewidth is notoriously difficult because the observed shape of the absorption line is generally given by a convolution of the homogenous (or natural) linewidth with the instrument response and a variety of inhomogenous broadening mechanisms. The latter include random strain fields induced by impurities and/or dislocations (16,17), and other fluctuations in the donor environment caused by chemical impurities and different isotopes in the natural composition of Si with differing nuclear moment (3)(4)(5). Time-domain methods such as ours (18,19) can directly measure the relaxation without any convolution, but require a short-pulse laser, in our case, a far-infrared free-electron laser.…”

Simultaneous Subsecond Hyperpolarization of the Nuclear and Electron Spins of Phosphorus in Silicon by Optical Pumping of Exciton Transitions

“…Several methods for achieving quantum logic with spin states of the shallow neutral donor (D 0 ) 31 P in 28 Si have been proposed [1,2,3] and the manipulation of electron and nuclear spin coherences have been demonstrated [4], but unsolved challenges include the measurement of single spins and the initialization, or polarization, of these spins. Fortuitously, the isotopic enrichment of 28 Si has another dramatic effect: the linewidths of many optical transitions are drastically reduced [9,10,11,12,13], including those involving 31 P. These narrow transitions have been proposed both for measurement of single spins [12,13,14] and for preferentially populating specific spin states [12,13].Electron and nuclear spin polarization in silicon has been studied for decades [15,16,17,18,19,20,21,22,23,24], but the nuclear polarization obtained to date has typically been less than a few percent, and requires thousands of seconds to establish. Very recently, a 31 P nuclear polarization of 68% has been reported [24] in a high magnetic field, using a variation of a mechanism first proposed in 1959 [17], and demonstrated in InSb in 1963 [18], but the time constant was still a relatively long 150 s. The method demonstrated here works at low magnetic field, and can simultaneously hyperpolarize both the electron and nuclear spins of 31 P in less than a second.…”