The synthesis of colloidal metal oxide nanocrystals with controlled shape is of fundamental and technological interest because in this way it is possible to tune their shape-dependent physical properties and thus consolidate their promising applications in optics, catalysis, biosensing, and data storage. Recently, the organic-solution phase [1][2][3] and liquid-solid-solution phase synthetic transfer routes [4] have been demonstrated to be versatile pathways toward such shape-controlled metal oxide nanocrystals. In all of these methods, organic surfactants play a key role in determining the growth and stability of nanocrystals. Combining this concept and the properties of supercritical water (SCW) will lead to a novel approach for the synthesis of metal oxide nanocrystals. For example, SCW is chemically stable and processing with it is environmentally benign; [5] it acts as a unique medium to aid in the spontaneous nucleation and crystallization of metal oxide nanoparticles; [6] and by using organic ligand molecules that are miscible with SCW, crystal growth can be limited and agglomeration can be inhibited in favor of small, well-dispersed particles. [7,8] As a well-known metal oxide, and because of its novel properties, ceria (CeO 2 ) has been extensively applied in catalysis, electrochemistry, and optics. For example, ceria nanocrystals have high oxygen-storage capability and act as an important component in three-way catalytic converters to clean up automotive exhausts.[9] To elevate catalytic activity, it is desirable to prepare ceria samples with a high surface area. So far, ceria nanocrystals with spherical, wire, rod, and tadpole shapes have been synthesized. [10] Along with this research, there is another recent trend aimed at tuning the ceria-crystal shape in order to expose reactive crystal planes for high reactivity.[11]Sayle et al. predicted in their theoretical study that the (100) surface is more reactive than (110) or (111) for the CeO 2 / YSZ(110) system (where YSZ is yttria-stabilized zirconia).[11a]Yan and co-workers synthesized ceria nanoparticles with various shapes using a hydrothermal method, and experimentally observed that cubic particles (ca. 36 nm) with exposed {100} crystal planes showed the highest oxygen-storage capacity.[11d]Despite these recent advances, it is still a great challenge to synthesize ceria nanocrystals of high quality in terms of uniform size, well-defined crystal shape, and ease of fabrication.Here, we report a simple and rapid approach for producing colloidal ceria nanocrystals on scales of less than 10 nm, with tailor-made ceria crystal planes, using organic-ligand-assisted supercritical water as the medium. The synthetic strategy is depicted in Figure 1. This strategy depends on: 1) sub-decananometer single-crystal formation in a supercritical hydrothermal process; [6] 2) the miscibility of the organic ligand molecules with high-temperature water, which is due to the lower dielectric constant of the water; [12] and 3) controlled nanocrystal growth from the ...

The OPERA neutrino experiment at the underground Gran Sasso Laboratory has measured the velocity of neutrinos from the CERN CNGS beam over a baseline of about 730 km. The measurement is based on data taken by OPERA in the years 2009, 2010 and 2011. Dedicated upgrades of the CNGS timing system and of the OPERA detector, as well as a high precision geodesy campaign for the measurement of the neutrino baseline, allowed reaching comparable systematic and statistical accuracies.An arrival time of CNGS muon neutrinos with respect to the one computed assuming the speed of light in vacuum of (6.5 ± 7.4 (stat.) +8.3 −8.0 (sys.)) ns was measured corresponding to a relative difference of the muon neutrino velocity with respect to the speed of light (v − c)/c = (2.7 ± 3.1 (stat.) +3.4 −3.3 (sys.)) × 10 −6 . The above result, obtained by comparing the time distributions of neutrino interactions and of protons hitting the CNGS target in 10.5 µs long extractions, was confirmed by a test performed at the end of 2011 using a short bunch beam allowing to measure the neutrino time of flight at the single interaction level.

Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms.

We present the case for a dark matter detector with directional sensitivity. This document was developed at the 2009 CYGNUS workshop on directional dark matter detection, and contains contributions from theorists and experimental groups in the field. We describe the need for a dark matter detector with directional sensitivity; each directional dark matter experiment presents their project's status; and we close with a feasibility study for scaling up to a one ton directional detector, which would cost around $150M.

We report a high-pressure single crystal study of the superconducting ferromagnet UCoGe. Acsusceptibility and resistivity measurements under pressures up to 2.2 GPa show ferromagnetism is smoothly depressed and vanishes at a critical pressure pc = 1.4 GPa. Near the ferromagnetic critical point superconductivity is enhanced. Upper-critical field measurements under pressure show Bc2(0) attains remarkably large values, which provides solid evidence for spin-triplet superconductivity over the whole pressure range. The obtained p − T phase diagram reveals superconductivity is closely connected to a ferromagnetic quantum critical point hidden under the superconducting 'dome'. PACS numbers: 74.70.Tx, 75.30.Kz, 74.62.Fj The recent discovery of superconductivity in itinerantelectron ferromagnets tuned to the border of ferromagnetic order [1,2,3,4] disclosed a new research theme in the field of magnetism and superconductivity. Notably, superconducting ferromagnets provide a unique testing ground [1,5] for superconductivity not mediated by phonons, but by magnetic interactions associated with a magnetic quantum critical point (QCP) [6,7,8]. In the 'traditional' model for spin-fluctuation mediated superconductivity [6] a second-order ferromagnetic quantum phase transition takes place when the Stoner parameter diverges, and near the critical point the exchange of longitudinal spin fluctuations stimulates spin-triplet superconductivity. Superconductivity is predicted to occur in the ferromagnetic as well as in the paramagnetic phase, while at the critical point the superconducting transition temperature T s → 0. Research into ferromagnetic superconductors will help to unravel how magnetic fluctuations can stimulate superconductivity. This novel insight might turn out to be crucial in the design of new superconducting materials.High-pressure experiments have been instrumental in investigating the interplay of magnetism and superconductivity. In the case of UGe 2 [1] superconductivity is found only in the ferromagnetic phase under pressure close to the critical point and at the critical pressure, p c , ferromagnetism and superconductivity disappear simultaneously. The ferromagnetic transition becomes first order for p → p c = 1.6 GPa [9]. Moreover, a field-induced first-order transition between two states with different polarizations was found in the ferromagnetic phase [10]. Superconductivity is attributed to critical magnetic fluctuations associated with this first order metamagnetic transition [11], rather than with critical spin fluctuations near p c . In UIr the ferro-to-paramagnetic phase transition remains second order under pressure all the way to p c = 2.8 GPa [3,12]. Superconductivity appears in the ferromagnetic phase in a small pressure range close to p c , however, it is not observed for p ≥ p c , which is at variance with the 'traditional' spin-fluctuation model [6]. In URhGe [2] ferromagnetism and superconductivity are observed at ambient pressure. Pressure raises the Curie temperature, T C , and drives the sy...

We report a high-pressure single crystal study of the topological superconductor Cu{x}Bi{2}Se{3}. Resistivity measurements under pressure show superconductivity is depressed smoothly. At the same time the metallic behavior is gradually lost. The upper-critical field data B{c2}(T) under pressure collapse onto a universal curve. The absence of Pauli limiting and the comparison of B{c2}(T) to a polar-state function point to spin-triplet superconductivity, but an anisotropic spin-singlet state cannot be discarded completely.

We report a high-pressure single-crystal study of the non-centrosymmetric superconductor YPtBi (Tc = 0.77 K). Magnetotransport measurements show a weak metallic behavior with a carrier concentration n ≃ 2.2 × 10 19 cm −3 . Resistivity measurements up to p = 2.51 GPa reveal superconductivity is promoted by pressure. The reduced upper critical field Bc2(T ) curves collapse onto a single curve, with values that exceed the model values for spin-singlet superconductivity. The Bc2 data point to an odd-parity component in the superconducting order parameter, in accordance with predictions for non-centrosymmetric superconductors.

The OPERA experiment was designed to search for ν_{μ}→ν_{τ} oscillations in appearance mode, i.e., by detecting the τ leptons produced in charged current ν_{τ} interactions. The experiment took data from 2008 to 2012 in the CERN Neutrinos to Gran Sasso beam. The observation of the ν_{μ}→ν_{τ} appearance, achieved with four candidate events in a subsample of the data, was previously reported. In this Letter, a fifth ν_{τ} candidate event, found in an enlarged data sample, is described. Together with a further reduction of the expected background, the candidate events detected so far allow us to assess the discovery of ν_{μ}→ν_{τ} oscillations in appearance mode with a significance larger than 5σ.