Sphere-to-rod transition of triblock copolymer micelles at room temperature

A room temperature sphere-to-rod transition of the polyethylene oxide-polypropylene oxide-polyethylene oxide-based triblock copolymer, (PEO)₂₀(PPO)₇₀ (PEO)₂₀ micelles have been observed in aqueous medium under the influence of ethanol and sodium chloride. Addition of 5–10% ethanol induces a high temperature sphere-to-rod transition of the micelles, which is brought to room temperature upon addition of NaCl. The inference about the change in the shape of the micelles has been drawn from small-angle neutron scattering (SANS) and viscosity studies.     

The thermoelectric powers of transition metals at high temperature

This paper is concerned with a survey of the experimental data for the thermoelectric power? The thermoelectric power is hereinafter referred to as TEP of transition metals and with their discussion. For the first time a critical review of the main data, which are given in the literature and proved to be rather incomplete, is presented. When necessary, the author has conducted the TEP measurements within the temperature range of 80° to 1800°k, wherever it was possible. For the first time TEP data have been obtained for scandium, osmium and, effectively, for hafnium; erroneous data for thorium and ruthenium have been corrected; the temperature measuring range for many other metals has been substantially extended. Finally, from the data found in the literature and the new results, a fairly complete notion has been formed of the high-temperature behaviour of TEP for all transition metals (except technetium) in the 3d, 4d, and 5d series of the periodic system, as well as for uranium and thorium. Some empirical regularities in the behaviour of TEP have been detected, the main one of which is that the TEP's of transition metals, which belong to a given column of the periodic table and are in a magnetically disordered state, vary with the temperature above 80°k in a similar way. The paper demonstrates that the TEP of transition metals is characterized by a complex, non-linear temperature dependence. Consequently, the value and sign of the TEP at room temperature cannot serve as a sufficient criterion for characterizing the TEP. The general shape (‘type’) of the TEP temperature curve should be used as the above-mentioned criterion.     

Freezing transition of interfacial water at room temperature under electric fields

The freezing of liquid water into ice was studied inside a gap of nanometer spacing under the control of electric fields and gap distance. The interfacial water underwent a sudden, reversible phase transition to ice in electric fields of 10(6) V m(-1) at room temperature. The critical field strength for the freezing transition was much weaker than that theoretically predicted for alignment of water dipoles and crystallization into polar cubic ice (>10(9) V m(-1)). This new type of freezing mechanism, occurring in weak electric fields and at room temperature, may have immediate implications for ice formation in diverse natural environments.     

Study of the modifications of the electric field gradient in hexafluorohafnates of transition metals above room temperature

The temperature dependence above room temperature of the hyperfine quadrupole interactions measured by the time differential perturbed angular correlations technique at hafnium sites in AHfF₆·nH₂O, with A=Co and Zn andn=6, 4 and 0, is presented. The different steps of the dehydration process are reflected by modifications on the hyperfine quadrupole parameters at increasing temperature. The changes in the electric field gradient as water molecules are lost are interpreted in terms of distortions induced in the [HfF₆]²⁻ octahedrons.     

Polariton condensates at room temperature

We review the recent developments of the polariton physics in microcavities featuring the exciton–photon strong coupling at room temperature, and leading to the achievement of room-temperature polariton condensates. Such cavities embed active layers with robust excitons that present a large binding energy and a large oscillator strength, i.e. wide bandgap inorganic or organic semiconductors, or organic molecules. These various systems are compared, in terms of figures of merit and of common features related to their strong oscillator strength. The various demonstrations of polariton laser are compared, as well as their condensation phase diagrams. The room-temperature operation indeed allows a detailed investigation of the thermodynamic and out-of-equilibrium regimes of the condensation process. The crucial role of the spatial dynamics of the condensate formation is discussed, as well as the debated issue of the mechanism of stimulated relaxation from the reservoir to the condensate under non-resonant excitation. Finally the prospects of polariton devices are presented.     

Subband spectroscopy at room temperature

Distinct resonances of the infrared excitation of surface subbands on Si(100) are observed to ～ 300 K. The linewidth is found to increase with rising temperature. We show that in general the optical width cannot be directly related to transport mobility.     

Conductance fluctuations of chiral metals

We study conductance fluctuations of the edge-state sheath that forms in the integer quantum Hall effect from the coupled edge states of a GaAs/Al_xGa_1 − xAs multilayer. Comparison of the measured variance in the vertical conductance to recent theoretical predictions for mesoscopic fluctuations suggests dephasing lengths of 1–10 μm around the sheath perimeter at low temperatures. However, inconsistencies in the estimated inelastic lengths indicate that present understanding of dephasing on the sheath is incomplete.     

A simple model for calculating the height of Schottky barriers at contacts of transition metals with silicon carbide polytypes

The heights of Schottky barriers at contacts of Ag, Au, Pd, Pt, Ti, Ru, Ni, Cr, Al, Mg, and Mn metals with different polytypes of silicon carbide SiC are self-consistently calculated in the framework of a simple model proposed earlier. The results of calculations performed for contacts of transition metals with silicon carbide polytypes are in quite reasonable agreement with experimental data under the assumption that silicon vacancies with an energy E_d=E_V+2.1 eV make a dominant contribution to the Schottky barrier height.     

Low temperature specific heat of transition metals and alloys

The article reviews experimental results on the low temperature specific heat of the transition metals and their alloys. Particularly discussed are the variations of the electronic part on the basis of a complete compilation of measurements given.     

Single-photon-level quantum memory at room temperature

Room-temperature, easy-to-operate quantum memories are essential building blocks for future long distance quantum information networks operating on an intercontinental scale, because devices like quantum repeaters, based on quantum memories, will have to be deployed in potentially remote, inaccessible locations. Here we demonstrate controllable, broadband and efficient storage and retrieval of weak coherent light pulses at the single-photon level in warm atomic cesium vapor using the robust far off-resonant Raman memory scheme. We show that the unconditional noise floor of this technically simple quantum memory is low enough to operate in the quantum regime, even in a room-temperature environment.     

Conductance quantization and magnetoresistance in magnetic point contacts

We theoretically study the electron transport through a magnetic point contact (PC) with special attention given to the effect of an atomic scale domain wall (DW). The spin precession of a conduction electron is forbidden in such an atomic scale DW and the sequence of quantized conductances depends on the relative orientation of magnetizations between left and right electrodes. The magnetoresistance is strongly enhanced for the narrow PC and oscillates with the conductance.     

Optical properties of KCP at room temperature

A fit of the reflectivity data of KCP is given using the expressions of the small polaron theory. It is further shown that small polaron theory gives the same optical properties as either a two site model with a deformation coordinate and Franck Condon transitions between the sites or a Peierls subband model for nearly free electrons.     

Hydrogen permeability of titanium at room temperature

The hydrogen permeability of titanium of grades VT1-00 and VT1-0 and of titanium iodide is investigated under saturation from glow-discharge plasma and in the cathodic process of the sulfuric acid electrolyte. A modified electrochemical method for investigating the hydrogen permeability of titanium at room temperature is proposed. Diffusion-coefficient values of hydrogen in titanium of differing purity are determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 51–54, April, 1982.     

Conductance oscillations of a spin-orbit stripe with polarized contacts

We investigate the linear conductance of a stripe of spin-orbit interaction in a 2D electron gas; that is, a 2D region of length l\ell along the transport direction and infinite in the transverse one in which a spin-orbit interaction of Rashba type is present. Polarization in the contacts is described by means of Zeeman fields. Our model predicts two types of conductance oscillations: Ramsauer oscillations in the minority spin transmission, when both spins can propagate, and Fano oscillations when only one spin propagates. The latter are due to the spin-orbit coupling with quasibound states of the non propagating spin. In the case of polarized contacts in antiparallel configuration Fano-like oscillations of the conductance are still made possible by the spin orbit coupling, even though no spin component is bound by the contacts. To describe these behaviors we propose a simplified model based on an ansatz wave function. In general, we find that the contribution for vanishing transverse momentum dominates and defines the conductance oscillations. Regarding the oscillations with Rashba coupling intensity, our model confirms the spin transistor behavior, but only for high degrees of polarization. Including a position dependent effective mass yields additional oscillations due to the mass jumps at the interfaces.     

Interphase interaction at indium phosphide contacts with metals of group I

The interphase interaction at indium phosphide contacts with layers of metals of group I (Cu, Ag, Au) annealed in an atmosphere of oxygen is investigated using the method of Rutherford backscattering, x-ray structure analysis, and electrophysical measurements. The relation between the character of the interphase process and the behavior of the electrophysical parameters of the Schottky barriers is traced. The mechanism of degradation in the contacts mentioned is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 8–13, January, 1986.     

Dynamic behavior of indium contacts with single crystals of cadmium sulfide above room temperature

Dark-current relaxation is observed with single crystals of cadmium sulfide after voltage has been applied. The kinetics of this reaction have been measured with respect to voltage and temperature. The observations are explained from the viewpoint of filling and emptying of electron traps in the contact regions of the crystals.     

Multiferroic phase transition near room temperature in BiFeO3 films

In multiferroic BiFeO(3) thin films grown on highly mismatched LaAlO(3) substrates, we reveal the coexistence of two differently distorted polymorphs that leads to striking features in the temperature dependence of the structural and multiferroic properties. Notably, the highly distorted phase quasiconcomitantly presents an abrupt structural change, transforms from a standard to a nonconventional ferroelectric, and transitions from antiferromagnetic to paramagnetic at 360±20 K. These coupled ferroic transitions just above room temperature hold promises of giant piezoelectric, magnetoelectric, and piezomagnetic responses, with potential in many applications fields.     

A method for determining the yield of indium bump contacts for integration in hybrid focal plane arrays at room temperature

A simple electrical method for determining the yield of indium bump integration between the infrared photosensing chip and the silicon readout chip in hybrid focal plane arrays (FPAs) is proposed. In our case, the IR photosensing chip consists of a 16 × 16 HgCdTe (MCT) photovoltaic (PV) array and the readout chip is a 16 × 16 silicon-CCD multiplexer (MUX). However, the method can be used for even larger array sizes. The method allows one to determine the yield of integration at room temperature. In addition, it does not necessitate the vacuum sealing of hybrid FPA in the dewar and subsequent testing at 77 K for determining this yield. The proposed method essentially verifies the electrical connectivity between the MCT PV diodes and their corresponding input diffusions in the CCD MUX on pixel-to-pixel basis. A simple examination of the readout of the whole array on the oscilloscope at room temperature, initiated at the detector and through CCD MUX is used for determining exactly how many MCT PV diodes have been joined successfully to their corresponding CCD MUX pixels after indium bump integration.     

Correlation between superconducting transition temperature and the cauchy discrepancy in body-centered-cubic transition metals

For body-centered-cubic transition metals, an empirical relationship exists between the superconducting transition temperature and the Cauchy discrepancy. This correlation may arise from many-atom effects.