Electrical Detection of Coherent Nuclear Spin Oscillations in Phosphorus-Doped Silicon Using Pulsed ENDOR

We demonstrate the electrical detection of pulsed X-band Electron Nuclear Double Resonance (ENDOR) in phosphorus-doped silicon at 5\,K. A pulse sequence analogous to Davies ENDOR in conventional electron spin resonance is used to measure the nuclear spin transition frequencies of the $^{31}$P nuclear spins, where the $^{31}$P electron spins are detected electrically via spin-dependent transitions through Si/SiO$_2$ interface states, thus not relying on a polarization of the electron spin system. In addition, the electrical detection of coherent nuclear spin oscillations is shown, demonstrating the feasibility to electrically read out the spin states of possible nuclear spin qubits.Comment: 5 pages, 3 figure

Measuring Group Velocity in Seismic Noise Correlation Studies Based on Phase Coherence and Resampling Strategies

Seismic noise cross correlation studies are of increasing importance in the seismological research community due to the ubiquity of noise sources and advances on how to use the seismic noise wave field for structural imaging and monitoring purposes. Stacks of noise cross correlations are now routinely used to extract empirical Green's functions between station pairs. In regional and global scale studies, mostly surface waves are extracted due to their dominance in seismic noise wave fields. Group arrival times measured from the time-frequency representation of frequency dispersive surface waves are further used in tomographic inversions to image seismic structure. Often, the group arrivals are not clearly identified or ambiguous depending on the signal and noise characteristics. Here, we present a procedure to robustly measure group velocities using the time-frequency domain phase-weighted stack (PWS) combined with data resampling and decision strategies. The time-frequency PWS improves signal extraction through incoherent signal attenuation during the stack of the noise cross correlations. Resampling strategies help to identify signals robust against data variations and to assess their errors. We have gathered these ingredients in an algorithm where the decision strategies and tuning parameters are reduced for semiautomated processing schemes. Our numerical and field data examples show a robust assignment of surface-wave group arrivals. The method is computational efficient thanks to an implementation based on pseudoanalytic frames of wavelets and enables processing large amounts of data.This work was supported in part by the Project MISTERIOS under Grant CGL2013-48601-C2-1-R, in part by the MIMOSA under Grant ANR-14-CE01-0012, in part by the COST Action ES1401 TIDES, in part by AGAUR, and in part by the FP7 Marie Curie Project through SV's Beatriu de Pinos Fellowship under Contract 600385. This is IPGP contribution 3814.Peer reviewe

Electrical detection of spin echoes for phosphorus donors in silicon

The electrical detection of spin echoes via echo tomography is used to observe decoherence processes associated with the electrical readout of the spin state of phosphorus donor electrons in silicon near a SiO$_2$ interface. Using the Carr-Purcell pulse sequence, an echo decay with a time constant of $1.7\pm0.2 \rm{\mu s}$ is observed, in good agreement with theoretical modeling of the interaction between donors and paramagnetic interface states. Electrical spin echo tomography thus can be used to study the spin dynamics in realistic spin qubit devices for quantum information processing.Comment: 14 pages, 3 figure

Detection of microseismic compressional (P) body waves aided by numerical modeling of oceanic noise sources

Among the different types of waves embedded in seismic noise, body waves present appealing properties but are still challenging to extract. Here we first validate recent improvements in numerical modeling of microseismic compressional (P) body waves and then show how this tool allows fast detection and location of their sources. We compute sources at ~0.2 Hz within typical P teleseismic distances (30-90°) from the Southern California Seismic Network and analyze the most significant discrete sources. The locations and relative strengths of the computed sources are validated by the good agreement with beam-forming analysis. These 54 noise sources exhibit a highly heterogeneous distribution, and cluster along the usual storm tracks in the Pacific and Atlantic oceans. They are mostly induced in the open ocean, at or near water depths of 2800 and 5600 km, most likely within storms or where ocean waves propagating as swell meet another swell or wind sea. We then emphasize two particularly strong storms to describe how they generate noise sources in their wake. We also use these two specific noise bursts to illustrate the differences between microseismic body and surface waves in terms of source distribution and resulting recordable ground motion. The different patterns between body and surface waves result from distinctive amplification of ocean wave-induced pressure perturbation and different seismic attenuation. Our study demonstrates the potential of numerical modeling to provide fast and accurate constraints on where and when to expect microseismic body waves, with implications for seismic imaging and climate studies. © 2013. American Geophysical Union. All Rights Reserved.This work was supported by the European Research Council (IOWAGA project), the Program >Investment for the future” Labex Mer (grant ANR-10-LABX-19-01), and the Consolider-Ingeno (Topo-Iberia). M.O. performed the data analysis while visiting the Domaines Océanique laboratorPeer Reviewe

Nucleation and growth of GaN nanorods on Si (111) surfaces by plasma-assisted molecular beam epitaxy - The influence of Si- and Mg-doping

The self-assembled growth of GaN nanorods on Si (111) substrates by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions is investigated. An amorphous silicon nitride layer is formed in the initial stage of growth that prevents the formation of a GaN wetting layer. The nucleation time was found to be strongly influenced by the substrate temperature and was more than 30 min for the applied growth conditions. The observed tapering and reduced length of silicon-doped nanorods is explained by enhanced nucleation on nonpolar facets and proves Ga-adatom diffusion on nanorod sidewalls as one contribution to the axial growth. The presence of Mg leads to an increased radial growth rate with a simultaneous decrease of the nanorod length and reduces the nucleation time for high Mg concentrations