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.     

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.     

Defect induced room temperature ferromagnetism in methylammonium lead iodide perovskite

The meteoric rise in the photovoltaic performance of organic-inorganic hybrid perovskite is a conspicuous reflection of its defect tolerance nature. The presence of lattice defect in organo lead halide perovskite can manipulate or even gives rise to some exceptional properties which otherwise would have remained unseen. One of such properties reported in this article is the experimental observation of defect mediated room temperature ferromagnetism in methylammonium lead halide perovskite for the very first time, ably supported by ab-initio calculations. Theoretical analysis predicts that the ferromagnetism principally arises from the iodine vacancies in the orthorhombic and cubic crystal phases but not in the tetragonal phase. The low temperature (100 K) ferromagnetic hysteresis loop was stable even at a high temperature of 380 K, substantiating the fact that the origin of magnetism embedded in its defective nature.     

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.     

Synthesis of homogeneous bunched lead molybdate nanobelts in large scale via vertical SLM system at room temperature

Large scale and homogeneous bunched lead molybdate nanobelts were synthesized via a vertically supported liquid membrane system in the presence of ethylenediamine at room temperature. The typical bunched nanobelts were of length of ca. 300–500 μm, the width of ca. 230–280 nm and the thickness of ca. 90–110 nm. The X-ray diffraction patterns showed that all the obtained PbMoO₄ crystals belonged to tetragonal structure. Scanning electron microscopy images revealed that the positioning of the two compartments in the SLM system, modifier additive and reacting time, highly affect the morphologies and sizes of PbMoO₄ crystals. Room-temperature emission spectra of PbMoO₄ were investigated and the relative photoluminescence intensity of 400 nm was intensified in PbMoO₄ nanobelts. A possible growth mechanism is proposed. PACS 81.07.-b; 87.15.-Mi; 78.67-n     

Infrared chiral anomaly at finite temperature

We study the Schwinger model at finite temperature and show that a temperature dependent chiral anomaly may arise from the long distance behavior of the electric field. At high temperature this anomaly depends linearly on the temperature T and is present not only in the two point function, but also in all even point amplitudes.     

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.     

室温下无耗散的量子自旋流

自旋电子学是近年来凝聚态物理研究中的一个热点．文章介绍了量子自旋流的概念，着重论述了一种新近出现的理论，其预言在一大类空穴掺杂的半导体中存在自旋流．计算了自旋流的大小，并论述了它在室温下无耗散的特性，最后给出了两种在实验中探测自旋流的方案．     

室温下无耗散的量子自旋流

自旋电子学是近年来凝聚态物理研究中的一个热点.文章介绍了量子自旋流的概念,着重论述了一种新近出现的理论,其预言在一大类空穴掺杂的半导体中存在自旋流.计算了自旋流的大小,并论述了它在室温下无耗散的特性,最后给出了两种在实验中探测自旋流的方案.     

Massive fermion dispersion relation at finite temperature

The extension to the massive case of fermionic excitations in a QED/QCD plasma at high temperature is studied in detail. Calculations for light massive fermions are performed over the whole range of the three-momentum. Analytical and numerical results show that the collective mode is no longer significant form>gT, whereas the usual particle excitation evolves rapidly to a free-particle state.     

Aggregation-based growth of silver nanowires at room temperature

We describe an aggregation-based growth mechanism for formation of silver nanowires at room temperature. It is found that the pH of solution and the concentration of l-cysteine capping molecules have an important effect on the formation and growth of nanowires. Characterization by atomic force microscopy (AFM) and UV-vis spectroscopy recorded as time clearly shows that the silver nanowires are grown at the expense of nanoparticles.     

Observation of exciton surface polaritons at room temperature

10 new cw far infrared laser lines have been observed by optically pumping the CD₃ deformation vibration band of CD₃OH with 9 μm CO₂-laser lines     

Possible observation of coulomb blockade at room temperature

We have studied the (I–V) characteristics of the tunnel junction formed between the tip and the substrate in an STM at room temperature. We find that in such an arrangement it may be possible to get a junction capacitance ⋍10⁻¹⁹ F and junction conductance <1μs. When the junction conductance is <1μs strong nonlinearity is observed in the (I–V) characteristics. We explain this nonlinearity as onset of coulomb blockade of tunneling electrons.     

Aggregate state of tin nanoparticles at room temperature

The aggregate state of tin nanoparticles produced by laser ablation of a solid target in liquid was studied. The study was performed using optical spectroscopy, electron and atomic-force microscopy, and photon correlation spectroscopy. Based on the experimental data obtained, it was shown that tin nanoparticles smaller than 50 nm are liquid under normal conditions. It is in agreement with presented theoretical estimates.     

X-ray diffraction study of KOCN at room temperature

The room temperature structure of KOCN has been successfully refined in space group I4/mcm. The OCN anion is disordered through 180° head-tail flipping and the positional coordinates and displacement parameters could not be separated for the N and O end atoms. The displacement parameters are compared for isomorphous KOCN, KN₃ and KSCN.