The proposed Mitchell Institute Neutrino Experiment at Reactor (MINER) experiment at the Nuclear Science Center at Texas A&M University will search for coherent elastic neutrino-nucleus scattering within close proximity (about 2 meters) of a 1 MW TRIGA nuclear reactor core using low threshold, cryogenic germanium and silicon detectors. Given the Standard Model cross section of the scattering process and the proposed experimental proximity to the reactor, as many as 5 to 20 events/kg/day are expected. We discuss the status of preliminary measurements to characterize the main backgrounds for the proposed experiment. Both in situ measurements at the experimental site and simulations using the MCNP and GEANT4 codes are described. A strategy for monitoring backgrounds during data taking is briefly discussed.

Intermetallic compounds and alloys are traditionally synthesized by heating mixtures of metal powders to high temperatures for long periods of time. A low-temperature solution-based alternative has been developed, and this strategy exploits the enhanced reactivity of nanoparticles and the nanometer diffusion distances afforded by binary nanocomposite precursors. Prereduced metal nanoparticles are combined in known ratios, and they form nanomodulated composites that rapidly transform into intermetallics and alloys upon heating at low temperatures. The approach is general in terms of accessible compositions, structures, and morphologies. Multiple compounds in the same binary system can be readily accessed; e.g., AuCu, AuCu3, Au3Cu, and the AuCu-II superlattice are all accessible in the Au-Cu system. This concept can be extended to other binary systems, including the intermetallics FePt3, CoPt, CuPt, and Cu3Pt and the alloys Ag-Pt, Au-Pd, and Ni-Pt. The ternary intermetallic Ag2Pd3S can also be rapidly synthesized at low temperatures from a nanocomposite precursor comprised of Ag2S and Pd nanoparticles. Using this low-temperature solution-based approach, a variety of morphologically diverse nanomaterials are accessible: surface-confined thin films (planar and nonplanar supports), free-standing monoliths, nanomesh materials, inverse opals, and dense gram-scale nanocrystalline powders of intermetallic AuCu. Importantly, the multimetallic materials synthesized using this approach are functional, yielding a room-temperature Fe-Pt ferromagnet, a superconducting sample of Ag2Pd3S (Tc = 1.10 K), and a AuPd4 alloy that selectively catalyzes the formation of H2O2 from H2 and O2. Such flexibility in the synthesis and processing of functional intermetallic and alloy materials is unprecedented.

We investigate the spin-current linear response conductivity tensor to an electric field in a paramagnetic two dimensonal electron gas with both Rashba and Dresselhaus spin-orbit coupling in the weak scattering regime. In the ususal case where both spin-orbit-split bands are occupied, we find that the spin-Hall conductivity depends only on the sign of the difference in magnitude of the Rashba and Dresselhaus coupling strengths except within a narrow window where both coupling strengths are equal. We also find a new effect in which a spin current is generated in the direction of the driving field whenever the Dresselhaus spin-orbit coupling is nonzero. We discuss experimental implications of this finding taking into account the finite mobility and typical parameters of current samples and possible experimental set ups for its detection.PACS numbers: 72.25.Dc,72.25.Hg, The manipulation of spin by electrical means in semiconducting enviroments has generated a lot of recent theoretical and experimental research aimed to develop useful spintonic devices and novel physical concepts [1], many focusing on effects that generate spin-polarized current [2]. Given the success of ferromagnetic metal based spintronic devices [3] which have revolutionized the information storage industry, the possibility of doping, gating, and heterojunction formation in seminconducting spintronic devices makes their possibilites that much wider. However, the practical implementation of semiconducting spintronics is awaiting the resolution of effective injection of spin-polarized carriers [4] from ferromagnetic metals combined with long spin lifetimes [5], or roomtemperature semiconductor ferromagnetism [6]. The recent discovery of the intrinsic spin-Hall effect by Murakami et al [7] in p-doped semiconductors and by Sinova et al [8] in Rashba spin-orbit coupled two dimensional electron gases (2EDGs) offers new avenues in spintronics research and transport phenomena which may meet the first challenge.The intrinsic spin-Hall effect consist of a dissipationless spin-current generated perpendicular to the driving electric field in the weak-scattering limit where spin-orbit coupling is strong. This effect contrasts with the extrinsic spin-Hall effect recently revived by Hirsch [9] and Zhang [10] and first studied by Dyakonov and Perel [11], where spin-orbit dependent scattering from impurities can generate a Hall spin-current but will vanish in the weak scattering limit, where the intrinsic effect dominates. The intrinsic spin-Hall effect predicted by Murakami et al [7,12] and Sinova et al [8,13] has generated interest within the theoretical community [14,15], supporting the need for a strong experimental effort in detecting such an effect. In the Rashba spin-orbit coupled 2DEGs it was shown that the intrinsic spin-Hall conductivity has a universal value e/8π in the case of both spin-split subbands being occupied [8,16]. Motivated by recent experiments [17,18] which have demonstrated the ability to tune the magnitude of the Rashba and Dresselhaus s...

No abstract

We demonstrate Josephson tunneling in vacuum tunnel junctions formed between a superconducting scanning tunneling microscope tip and a Pb film, for junction resistances in the range 50-300 kΩ. We show that the superconducting phase dynamics is dominated by thermal fluctuations, and that the Josephson current appears as a peak centered at small finite voltage. In the presence of microwave fields (f = 15.0 GHz) the peak decreases in magnitude and shifts to higher voltages with increasing rf power, in agreement with theory. 07.79. Cz, 74.40.+k, 74.50.+r Scanning tunneling microscopy (STM) has been extensively used in the study of high-T c superconductors (HTSC), providing a spectroscopic tool with unparalleled energy and spatial resolution. Yet, while superconducting tips have been demonstrated in the past [1] all STM studies so far have been performed using normal-metal tips, thus probing only the single-particle excitation spectrum, the gap structure which is a consequence of superconductivity, but not the superconducting (SC) ground state itself. Results from STM measurements of HTSC show excitation gaps in situations where superconductivity is believed to be absent (pseudo-gap), such as in vortex cores [2] and above T c in underdoped samples [3], as well as inhomogenieties in the gap structure in reportedly high quality BiSrCaCuO crystals [4]. These results, due to the nature of the measurements, do not remove the ambiguity with respect to the existence of a finite SC pair amplitude in the situations studied.