731 research outputs found
Lasing in Bose-Fermi mixtures
No full textA.K. acknowledges the support from the EPSRC Established Career Fellowship. V.K., M.D., V.F.S. and A.K. acknowledge support from the Russian Ministry of Science and Education, contract (contract No. 11.G34.31.0067). P.G.S. acknowledges support from Greek GSRT program Aristeia (grant No. 1978). C.S., M. A. J.F., M.K and S.H. acknowledge support from the state of Bavaria.Light amplification by stimulated emission of radiation, well-known for revolutionising photonic science, has been realised primarily in fermionic systems including widely applied diode lasers. The prerequisite for fermionic lasing is the inversion of electronic population, which governs the lasing threshold. More recently, bosonic lasers have also been developed based on Bose-Einstein condensates of exciton-polaritons in semiconductor microcavities. These electrically neutral bosons coexist with charged electrons and holes. In the presence of magnetic fields, the charged particles are bound to their cyclotron orbits, while the neutral exciton-polaritons move freely. We demonstrate how magnetic fields affect dramatically the phase diagram of mixed Bose-Fermi systems, switching between fermionic lasing, incoherent emission and bosonic lasing regimes in planar and pillar microcavities with optical and electrical pumping. We collected and analyzed the data taken on pillar and planar microcavity structures at continuous wave and pulsed optical excitation as well as injecting electrons and holes electronically. Our results evidence the transition from a Bose gas to a Fermi liquid mediated by magnetic fields and light-matter coupling.Peer reviewe
Read Book [PDF] Back from the Dead: Inside the Subhas Bose Mystery Full-Acces
No full textRead Or Download Back from the Dead: Inside the Subhas Bose Mystery Full Books By by Anuj Dhar (Journalist (Author), Hindustan Times) (Author)
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Three-dimensional structure of quantized vortices in rotating Bose-Einstein condensates
No full textBose-Einstein condensates (BEC) are ideal superfluid systems to realize quantum turbulence (QT): vortex cores in BECs are larger than in superfluid Helium, making easier their observation. Recent experimental and numerical studies reported that vortex states in BEC can evolve towards a turbulent regime when an oscillatory excitation is applied. We discuss in this work how to accurately prepare initial states with vortices before running numerical simulations of QT based on the Gross-Pitaevskii equation. The case of a dense Abrikosov lattice in a fast rotating BEC is presented. High resolution numerical simulations using parallel computing are used to accurately capture physically important features of the vortices (vortex radius, inter-vortex spacing, vortex density profile)
Bose–Einstein condensation in the Rindler space
No full textAbstractBased on the Unruh effect, we calculate the critical acceleration of the Bose–Einstein condensation in a free complex scalar field at finite density in the Rindler space. Our model corresponds to an ideal gas performing constantly accelerating motion in a Minkowski space–time at zero-temperature, where the gas is composed of the complex scalar particles and it can be thought to be in a thermal-bath with the Unruh temperature. In the accelerating frame, the model will be in the Bose–Einstein condensation state at low acceleration; on the other hand, there will be no condensation at high acceleration by the thermal excitation brought into by the Unruh effect. Our critical acceleration is the one at which the Bose–Einstein condensation begins to appear in the accelerating frame when we decrease the acceleration gradually. To carry out the calculation, we assume that the critical acceleration is much larger than the mass of the particle
Fermi-Bose supersymmetry (supergauge symmetry in four dimensions)
No full textThe author explains the ideas of Fermi-Bose supersymmetry and presents examples to show how the construction of realistic models may be attempted. (24 refs)
Chemisorption on binary alloys with long-range order
No full textPT: J; CR: BERK NF, 1975, SURF SCI, V48, P289 BOSE SM, 1981, PHYS REV B, V24, P1934 FOO EN, 1970, PHYS REV LETT, V25, P1748 HELLWEGE KH, 1981, LANDOLTBORNSTEIN N A, V13, P406 KALKSTEIN D, 1971, SURF SCI, V26, P85 MORANLOPEZ JL, 1975, J PHYS F MET PHYS, V5, P1277 MORANLOPEZ JL, 1976, SURF SCI, V57, P540 NEWNS DM, 1969, PHYS REV, V178, P1123 SOVEN P, 1967, PHYS REV, V156, P809 SULSTON KW, 1986, PHYS REV B, V33, P2263 UEBA H, 1979, J CHEM PHYS, V70, P1745 UEBA H, 1979, PHYS STATUS SOLIDI B, V92, P307 VANSANTEN RA, 1975, SURF SCI, V53, P35 VANSANTEN RA, 1977, SURF SCI, V63, P358; NR: 14; TC: 2; J9: PHYS REV B; PG: 4; GA: P4638Source type: Electronic(1
Modification of Loop 1 Affects the Nucleotide Binding Properties of Myo1c, the Adaptation Motor in the Inner Ear
No full textMyo1c is one of eight members of the mammalian myosin I family of actin-associated molecular motors. In stereocilia of the hair cells in the inner ear, Myo1c presumably serves as the adaptation motor, which regulates the opening and closing of transduction channels. Although there is conservation of sequence and structure among all myosins in the N-terminal motor domain, which contains the nucleotide- and actin-binding sites, some differences include the length and composition of surface loops, including loop 1, which lies near the nucleotide-binding domain. To investigate the role of loop 1, we expressed in insect cells mutants of a truncated form of Myo1c, Myo1c1IQ, as well as chimeras of Myo1c1IQ with the analogous loop from other myosins. We found that replacement of the charged residues in loop 1 with alanines or the whole loop with a series of alanines did not alter the ATPase activity, transient kinetics properties, or Ca2+ sensitivity of Myo1c1IQ. Substitution of loop 1 with that of the corresponding region from tonic smooth muscle myosin II (Myo1c1IQ-tonic) or replacement with a single glycine (Myo1c1IQ-G) accelerated the release of ADP from A.M 2?3-fold in Ca2+, whereas substitution with loop 1 from phasic muscle myosin II (Myo1c1IQ-phasic) accelerated the release of ADP 35-fold. Motility assays with chimeras containing a single ?-helix, or SAH, domain showed that Myo1cSAH-tonic translocated actin in vitro twice as fast as Myo1cSAH-WT and 3-fold faster than Myo1cSAH-G. The studies show that changes induced in Myo1c via modification of loop 1 showed no resemblance to the behavior of the loop donor myosins or to the changes previously observed with similar Myo1b chimeras
Light-induced atomic desorption in a compact system for ultracold atoms
No full textThis work was supported by the UK EPSRC grant GR/T08272/01 and the Leverhulme Trust Research Project Grant RPG-2013-074. G.S. acknowledges support from a SUPA Advanced Fellowship.In recent years, light-induced atomic desorption (LIAD) of alkali atoms from the inner surface of a vacuum chamber has been employed in cold atom experiments for the purpose of modulating the alkali background vapour. This is beneficial because larger trapped atom samples can be loaded from vapour at higher pressure, after which the pressure is reduced to increase the lifetime of the sample. We present an analysis, based on the case of rubidium atoms adsorbed on pyrex, of various aspects of LIAD that are useful for this application. Firstly, we study the intensity dependence of LIAD by fitting the experimental data with a rate-equation model, from which we extract a correct prediction for the increase in trapped atom number. Following this, we quantify a figure of merit for the utility of LIAD in cold atom experiments and we show how it can be optimised for realistic experimental parameters.Peer reviewe
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