Quantum mechanical single-gold-nanocluster electroluminescent light source at room temperature

Electrically contacted gold-nanocluster arrays formed within electromigration-induced break junctions exhibit bright, field-dependent electroluminescence in the near infrared (650-800 nm). Intensity autocorrelation of spatially isolated individual nanocluster emission driven at high electrical frequency (f(ac)= approximately 200 MHz) reveals antibunched electroluminescence at room temperature. These results demonstrate the single quantum nature of several-atom gold molecules and suggest their use as room-temperature electrically driven single-photon sources.     

Quantum conductance oscillations in metal/molecule/metal switches at room temperature

We apply pressure-modulated conductance microscopy to metal/molecule/metal switches. Apart from pressure-induced conductance peaks that indicate nanoscale conducting pathways, we also observe dips and oscillations for devices with conductance between 1 and 2 conductance quantum. The conductance oscillations arise from interfering electron waves along one or two quantum conductance channels between two partially transmitting electrode surfaces at room temperature, underscoring these devices' potential as coherent, atomic-scale switches.     

Surface energy of liquid metals at the melting temperature related to bulk liquid structure

The product σχ_Tm of surface energy σ and isothermal compressibility σχ_Tm for liquid metals at the melting temperature T_m yields a length l ranging from about 0.2 to 0.5 Å over the entire range of liquid metals. The variation of l, which has been related brfore to the thickness of the liquid-vapour interface, is shown to be accurately represented by , where the constant c is determined empirically, K_B and N being the Boltzmann factor and Avogadro's number respectively, and S_Tm(0) the bulk liquid structure factor in the long wavelength limit at the melting temperature. A microscopic interpretation of l is proposed.     

还原温度对氧化石墨烯结构及室温下H_2敏感性能的影响

以氧化石墨凝胶制备的氧化石墨烯(GO)溶胶为前驱体,在100—350℃温度下还原获得不同还原程度的还原氧化石墨烯(rGO)样品,并采用旋涂工艺制备还原氧化石墨烯气敏薄膜元件.采用X射线衍射、拉曼光谱、傅里叶变换红外光谱和气敏测试等手段研究还原温度对样品结构、官能团和气敏性能的影响.结果表明:经热还原处理的氧化石墨烯结构向较为有序的类石墨结构转变,还原温度为200℃时,样品处于GO向rGO转变的过渡阶段,还原温度达到250℃时,则表现出还原氧化石墨烯特性;无序程度随还原温度的升高先由0.85增大至1.59,随后减小至1.41,总体呈现增加趋势;氧化石墨烯表面含氧官能团随还原温度的升高逐渐热解失去,不同含氧官能团的失去温度范围不同;热还原氧化石墨烯具有优异的室温H_2敏感性能,随着还原温度的升高,元件灵敏度逐渐减小,响应-恢复时间逐渐增大,最佳灵敏度为88.56%,响应时间为30 s.     

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.     

Hydrogen diffusion in titanium at room temperature

The diffusion of hydrogen in technically pure VT1-00 titanium is studied at room temperature under conditions of hydrogen penetration from a glow discharge plasma. Hydrogen penetration occurs under conditions of hydride phase growth. The diffusion coefficients of hydrogen in titanium at room temperature are estimated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 43–47, March, 1982.     

Ferromagnetism in InMnAs layers at room temperature

The InMnAs layers with ferromagnetic properties at room temperature are prepared by laser ablation. This is confirmed by the results of investigating the anomalous Hall and magneto-optical Kerr effects and by magnetic-force microscopy. According to x-ray diffraction data, the InMnAs layers have a fairly high crystal quality but contain inclusions of the MnAs hexagonal phase. An analysis of the electrical properties of the InMnAs layers suggests that the ferromagnetism revealed at room temperature cannot be accounted for by the presence of the MnAs phase but is associated with the charge carrier transfer in the InMnAs matrix.     

Quantum electrodynamics at finite temperature

We present a systematic examination of finite temperature effects in quantum electrodynamics at one loop order. We calculate mass, charge, and wavefunction renormalization, demonstrate the running of the coupling constant at high temperatures, and study the renormalized vertex function and the energy momentum tensor. The confusion in the literature concerning the finite temperature corrections to the electron's magnetic moment is resolved. We also present the finite temperature effects in scalar electrodynamics. Throughout we stress the need to provide a well-defined method to observe a given quantity when interpreting the results of a calculation, and we suggest new techniques which incorporate the novel features of finite temperature theories.     

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.     

Optical bistability effects in a Tm,Ho:YLF laser at room temperature

We demonstrate strong optical bistability in a 2 microm continuous-wave Tm,Ho:YLF laser pumped by a 792 nm laser diode near room temperature. The bistable region is as much as 100 mW wide at 283 K and can be controlled by the temperature of the laser crystal. The influence of crystal temperature on the characteristics of optical bistability is obtained. The influence of the pump-to-mode ratio on the bistable characteristics of the laser is also discussed. To our knowledge this is the first report of optical bistability effects in Tm,Ho:YLF lasers.     

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.     

On slip in AgCl crystals at room temperature

At moderately wavy and branched slip bands on the surfaces of sheets of AgCl crystals the distribution of slip lines has been observed by means of the electron microscope. From the results it can be deduced that the cross slip of screw dislocations takes place. The divergence of the ends of slip bands has also been observed, which can be as well explained by the cross slip. From the active slip direction and the directions of straight slip lines in the cross-slip regions the microscopic slip planes have been determined. They lie in the region roughly limited by the {113} and {331} planes and the problem is discussed whether these planes are low-index crystallographic planes.     

On the fluorescence of C_60 at room temperature

The fluorescence properties of C 60 in different organic solvents have been investigated at room temperature. Three fluorescence emission centers are discovered and ascribed to different aggregations of C 60 in solvent. A series of blue fluorescence peaks centered at 440 nm derive from C 60 nanoparticles; a distinctive yellow-green fluorescence band in 575 nm region arises from the aggregates of C 60 nanoparticles; a more informative salmon fluorescence band around 700 nm originates from C 60 microcrystals....     

Quantum chaos in the Yang-Mills-Higgs system at finite temperature

Quantum chaos in the finite-temperature Yang-Mills-Higgs system is studied. The energy spectrum of a spatially homogeneous SU(2) Yang-Mills-Higgs system is calculated within thermofield dynamics. Level statistics of the spectra is studied by plotting nearest-level spacing distribution histograms. It is found that finite-temperature effects lead to a strengthening of chaotic effects, i.e. a spectrum which has the Poissonian distribution at zero temperature has the Gaussian distribution at finite temperature.Received: 18 August 2004, Revised: 23 March 2005, Published online: 22 June 2005PACS: 05.45.-a,11.10.Wx, 11.15.-q     

Deformation luminescence in KCl irradiated at room temperature

It has been found that there is a relationship between the thermoluminescence and the deformation luminescence of irradiated pure KCl samples. It is concluded that the luminescent process in the deformation luminescence is the recombination of interstitial halogen atoms with vacancy centres (F, M) as well as in the thermoluminescence.     

Observation of relaxation modes in room temperature ferroelectric liquid crystal mixtures

The dielectric measurements in SmC* and SmA phases of a room temperature ferroelectric liquid crystal mixture FLC-6980 in the cells of different thickness in planer alignment have been carried out in the frequency range 100 Hz to 1 MHz. A relaxation mode (called NRM) whose dielectric increment is less than the Goldstone mode has been observed in the SmC* phase. This mode appears due to the surface effect. Goldstone mode and the soft mode was observable in the vicinity of SmC*-SmA transition temperature (T _C*A). The dielectric parameters of the Goldstone mode, new mode and the soft mode have been studied as a function of frequency and temperature. The calculated values for f_NRM, δε^NRM and distribution parameter α_NRM are found to be 325 kHz, 6 and 0.156 for 5μm thick planer cell at 37°C. It is seen that in the vicinity of theT _C*A, soft mode obeys the Curie-Weiss law given by mean field theory. The results have been compared with materials of large spontaneous polarization.     

Quantum yield and decay of nitrogen afterglow with a carbon impurity at the temperature of liquid nitrogen

The article presents the results of an investigation of the quantum yield and absolute population of the vibrational levels of electronically excited states A² (v 25), B² (v 15) of the CN radical and B³_g (v 12) of the N₂ molecule in nitrogen-helium afterglow cooled by liquid nitrogen at a total pressure of the mixture of (12–20) mm Hg. The rotational temperature of the cold gas was measured. The content of carbon impurity in the system was measured by the spectral method. A study was made of the kinetics of the decay of afterglow, from which the relaxation time was determined and the cross section of exchange of vibrational quanta between N₂ and CN molecules was estimated. The data obtained were compared with the results of investigating nitrogen-helium afterglow under room-temperature conditions.300th Anniversity of Reunion of Ukraine with Russia Dnepropetrovsk State University.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 52–59, April, 1976.