31,794 research outputs found

    Charge density wave in hidden order state of URu2_2Si2_2

    Full text link
    We argue that the hidden order state in URu2_2Si2_2 will induce a charge density wave. The modulation vector of the charge density wave will be twice that of the hidden order state, QCDW=2QHOQ_{CDW} = 2Q_{HO}. To illustrate how the charge density wave arises we use a Ginzburg-Landau theory that contains a coupling of the charge density wave amplitude to the square of the HO order parameter ΔHO\Delta_{HO}. This simple analysis allows us to predict the intensity and temperature dependence of the charge density wave order parameter in terms of the susceptibilities and coupling constants used in the Ginzburg-Landau analysis.Comment: 8 pages, 4 figure

    Absorption and Emission in the non-Poisson case

    Full text link
    This letter adresses the challenging problems posed to the Kubo-Anderson (KA) theory by the discovery of intermittent resonant fluorescence with a non-exponential distribution of waiting times. We show how to extend the KA theory from aged to aging systems, aging for a very extended time period or even forever, being a crucial consequence of non-Poisson statistics.Comment: 4 pages 3 figures. accepted for publication on Physical Review Letter

    Optical Investigations of Charge Gap in Orbital Ordered La1/2Sr3/2MnO4

    Full text link
    Temperature and polarization dependent electronic structure of La1/2Sr3/2MnO4 were investigated by optical conductivity analyses. With decreasing temperature, for E//ab, a broad mid-infrared (MIR) peak of La1/2Sr3/2MnO4 becomes narrower and moves to the higher frequency, while that of Nd1/2Sr3/2MnO4 nearly temperature independent. We showed that the MIR peak in La1/2Sr3/2MnO4 originates from orbital ordering associated with CE-type magnetic ordering and that the Jahn-Teller distortion has a significant influence on the width and the position of the MIR peak.Comment: 10 pages, 4 figure

    Melting of Charge/Orbital Ordered States in Nd1/2_{1/2}Sr1/2_{1/2}MnO3_3: Temperature and Magnetic Field Dependent Optical Studies

    Full text link
    We investigated the temperature (T=T= 15 \sim 290 K) and the magnetic field (H=H= 0 \sim 17 T) dependent optical conductivity spectra of a charge/orbital ordered manganite, Nd1/2_{1/2}Sr1/2_{1/2}MnO3_3. With variation of TT and HH, large spectral weight changes were observed up to 4.0 eV. These spectral weight changes could be explained using the polaron picture. Interestingly, our results suggested that some local ordered state might remain above the charge ordering temperature, and that the charge/orbital melted state at a high magnetic field (i.e. at H=H= 17 T and % T= 4.2 K) should be a three dimensional ferromagnetic metal. We also investigated the first order phase transition from the charge/orbital ordered state to ferromagnetic metallic state using the TT- and HH% -dependent dielectric constants ϵ1\epsilon_1. In the charge/orbital ordered insulating state, ϵ1\epsilon_1 was positive and dϵ1/dω0d\epsilon_1/d\omega \approx 0. With increasing TT and HH, ϵ1\epsilon_1 was increased up to the insulator-metal phase boundaries. And then, ϵ1\epsilon_1 abruptly changed into negative and dϵ1/dω>0d\epsilon_1/d\omega >0, which was consistent with typical responses of a metal. Through the analysis of ϵ1% \epsilon_1 using an effective medium approximation, we found that the melting of charge/orbital ordered states should occur through the percolation of ferromagnetic metal domains.Comment: submitted to Phys. Rev.

    Nearly Massless Electrons in the Silicon Interface with a Metal Film

    Full text link
    We demonstrate the realization of nearly massless electrons in the most widely used device material, silicon, at the interface with a metal film. Using angle-resolved photoemission, we found that the surface band of a monolayer lead film drives a hole band of the Si inversion layer formed at the interface with the film to have nearly linear dispersion with an effective mass about 20 times lighter than bulk Si and comparable to graphene. The reduction of mass can be accounted for by repulsive interaction between neighboring bands of the metal film and Si substrate. Our result suggests a promising way to take advantage of massless carriers in silicon-based thin-film devices, which can also be applied for various other semiconductor devices.Comment: 4 pages, 4 figures, accepted for publication in Physical Review Letter

    Recent Progress in Droplet-Based Manufacturing Research

    Get PDF
    This article reports the recent progress of re-search made in the Droplet-Based Manufacturing Laboratory at MIT. The study has been focused on obtaining a fundamental understanding of microdroplet deposition and applying the technology to various practical applications. Specific scientific contributions include the development of an analytical model for droplet splashing/recoiling, an in situ droplet size control methodology, and a study of microstructure design for spray forming. The research per-formed in the lab provides both fundamental knowledge base and practical process developments for a range of manufacturing applications, including electronics packaging, spray forming and freeform fabrication.Singapore-MIT Alliance (SMA

    Prompt photon hadroproduction at high energies in off-shell gluon-gluon fusion

    Full text link
    The amplitude for production of a single photon associated with quark pair in the fusion of two off-shell gluons is calculated. The matrix element found is applied to the inclusive prompt photon hadroproduction at high energies in the framework of kt-factorization QCD approach. The total and differential cross sections are calculated in both central and forward pseudo-rapidity regions. The conservative error analisys is performed. We used the unintegrated gluon distributions in a proton which were obtained from the full CCFM evolution equation as well as from the Kimber-Martin-Ryskin prescription. Theoretical results were compared with recent experimental data taken by the D0 and CDF collaborations at Fermilab Tevatron. Theoretical predictions for the LHC energies are given.Comment: 32 pages, 18 figure

    Non-Markovian stochastic Liouville equation and anomalous relaxation kinetics

    Full text link
    The kinetics of phase and population relaxation in quantum systems induced by noise with anomalously slowly decaying correlation function P (t) ~ (wt)^{- alpha}, where 0 < alpha < 1 is analyzed within continuous time random walk approach. The relaxation kinetics is shown to be anomalously slow. Moreover for alpha < 1 in the limit of short characteristic time of fluctuations w^{-1} the kinetics is independent of w. As alpha \to 1 the relaxation regime changes from the static limit to fluctuation narrowing. Simple analytical expressions are obtained describing the specific features of the kinetics.Comment: 7 pages, 2 figure
    corecore