共查询到20条相似文献,搜索用时 31 毫秒
1.
Fretwell HM Kaminski A Mesot J Campuzano JC Norman MR Randeria M Sato T Gatt R Takahashi T Kadowaki K 《Physical review letters》2000,84(19):4449-4452
We study the Fermi surface of Bi2Sr2CaCu2O8 using angle resolved photoemission spectroscopy (ARPES) with a momentum resolution of approximately 0.01 of the Brillouin zone. We show that, contrary to recent suggestions, the ARPES derived Fermi surface is a large hole barrel centered at (pi,pi), independent of the incident photon energy. We caution that the photon energy and k dependence of the matrix elements, if not properly accounted for, can lead to misinterpretation of ARPES intensities. 相似文献
2.
The signatures of the inner product matrices on a Lei algebra's highest weight representation are encoded in the representation's signature character. We show that the signature characters of a finite-dimensional Lie algebra's highest weight representations obey simple difference equations that have a unique solution once appropriate boundary conditions are imposed. We use these results to derive the signature characters of allA
2 andB
2 highest weight representations. Our results extend, and explain, signature patterns analogous to those observed by Friedan, Qiu and Shenker in the Virasoro algebra's representation theory. 相似文献
3.
《Composite Interfaces》2013,20(2):205-212
We investigate the adsorption behavior of methyl orange (MO) on composite xerogels. Mesoporous TiO2-SiO2 and TiO2-SiO2-Al2O3 xerogels are prepared by hydrolysis of tetraethyl orthosilicate (TEOS), tetrabutyl orthotitanate (TBOT), and AlCl3 ·6H2O using HCl as a catalyst and cetyltrimethylammonium bromide (CTAB) as a templating agent. The corresponding microporous xerogels are also prepared without addition of CTAB. These xerogels are then characterized by XRD, FTIR, and BET.We find that MO is adsorbed by the mesoporous xerogels in acidic solutions, showing Langmuir type adsorption isotherms. We also find that the adsorption decreases with increasing temperature. It is suggested that adsorption exhibits a sieve effect and that MO is adsorbed through electrostatic attraction and hydrogen bonding between MO and the xerogels. 相似文献
4.
《Nuclear Physics B》1995,444(3):468-486
In this paper we construct a (2,2) dimensional string theory with manifest N = 1 spacetime supersymmetry. We use Berkovits' approach of augmenting the spacetime supercoordinates by the conjugate momenta for the fermionic variables. The worldsheet symmetry algebra is a twisted and truncated “small” N = 4 superconformal algebra. The realisation of the symmetry algebra is reducible with an infinite order of reducibility. We study the physical states of the theory by two different methods. In one of them, we identify a subset of irreducible constraints, which is by itself critical. We construct the BRST operator for the irreducible constraints, and study the cohomology and interactions. This method breaks the SO(2,2) spacetime symmetry of the original reducible theory. In another approach, we study the theory in a fully covariant manner, which involves the introduction of infinitely many ghosts for ghosts. 相似文献
5.
6.
Xiaoli Zhao 《中国物理 B》2022,31(8):83402-083402
We present elastic electron scattering cross sections with holmethane molecules CH2Br2 and CCl2Br2 in the low-energy region ranging from 0.01 eV to 20 eV. The calculations are performed with the R-matrix method in static-exchange plus polarization (SEP) and close-coupling (CC) approximations. The integral, differential, and momentum transfer cross sections are calculated. The convergence of the obtained cross sections is checked at four different levels of SEP approximation. The predicted positions of the resonances agree well with available results. The precise resonance parameters are found to be sensitive to the treatment of polarization effects employed. We find that the polarization has a substantial effect on the cross sections, and this effect becomes even more important for lower impact energies. 相似文献
7.
J. Schwenk W. B. Schmidke S. P. Vokos 《Zeitschrift fur Physik C Particles and Fields》1990,46(4):643-646
We construct the quantum supergroupGL q(1/1) in its matrix representation. We investigate properties of powers of 2×2 quantum super-matrices and we show that any element ofGL q(1/1) can be written as the exponential of a matrix with non-commuting entries. An explicit construction of this exponential form is presented. Finally, we prove a relation between the quantum superdeterminant of a quantum matrix and the supertrace of the logarithm of the quantum matrix. 相似文献
8.
Kohsaka Y Iwaya K Satow S Hanaguri T Azuma M Takano M Takagi H 《Physical review letters》2004,93(9):097004
The spatial variation of electronic states was imaged in the lightly doped Mott insulator Ca(2-x)NaxCuO2Cl2 using scanning tunneling microscopy or spectroscopy. We observed nanoscale domains with a high local density of states within an insulating background. The observed domains have a characteristic length scale of 2 nm (approximately 4-5a, a: lattice constant) with preferred orientations along the tetragonal [100] direction. We argue that such spatially inhomogeneous electronic states are inherent to slightly doped Mott insulators and play an important role for the insulator to metal transition. 相似文献
9.
We proposed a 1 × 2 and 2×2 SOI switches for applying in fiber optic communication network. The optical path loss and signal-to-noise ratio are evaluated and compared in this paper. 相似文献
10.
CV Tomy D Pal SS Banerjee S Ramakrishnan AK Grover S Bhattacharya MJ Higgins G Balakrishnan McK Paul 《Pramana》2002,58(5-6):925-935
The weakly pinned single crystals of the hexagonal 2H-NbSe2 compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder
transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of
the peak effect phenomenon in three crystals of 2H-NbSe2, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of
a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability
effects and pinning. 相似文献
11.
12.
Zhao JianFa Cao LiPeng Li WenMin Zhang Jun Dai GuangYang Yu Shuang Liu QingQing Wang XianCheng Zhao GuoQiang Jia YaTing Duan Lei Long YouWen Lin Hong-Ji Chen Chien-Te Tjeng Liu-Hao Hu ZhiWei Yu RunZe Jin ChangQing 《中国科学:物理学 力学 天文学(英文版)》2019,62(10):1-5
We present a first-principles investigation on the dynamics and mechanism of the oxidation reaction between water molecules and the reduced PuO_2(110) surface using ab initio molecular dynamics(AIMD) simulations in combination with density functional theory(DFT) + U calculations. We find a dominating dissociation preference of water molecules for the vacancy defect sites on the PuO_2(110) surface, irrespective of the water or vacancy coverage. Due to hybridizations between the frontier orbitals of water molecule and the electronic states of the vacancy vicinity, partial water dissociation at the vacancy sites is exothermic and barrierless. The dissociation product, an OH group, further hydrogenates the PuO_2(110) surface by occupying the vacancy site.We also observe surface vacancy diffusion induced by the interactions between the water molecules and the surface oxygen atom in the proximity of the defect sites. 相似文献
13.
Kendziora CA Sergienko IA Jin R He J Keppens V Sales BC Mandrus D 《Physical review letters》2005,95(12):125503
We have measured the polarized Raman scattering spectra of Cd2Re2O7, the first superconducting pyrochlore, as a function of temperature. For temperatures below the cubic-to-tetragonal structural phase transition (SPT) at 200 K, a peak with B1 symmetry develops at zero frequency with divergent intensity. We identify this peak as the first observation of the Goldstone phonon in a crystalline solid. The Goldstone phonon is a collective excitation that exists due to the breaking of the continuous symmetry with the SPT. Its emergence coincides with that of a Raman-active soft mode. The order parameter for both features derives from an unstable doubly degenerate vibration (with Eu symmetry) of the O1 atoms which drives the SPT. 相似文献
14.
We propose a definition of symplectic 2-groupoid which includes integrations of Courant algebroids that have been recently constructed. We study in detail the simple but illustrative case of constant symplectic 2-groupoids. We show that the constant symplectic 2-groupoids are, up to equivalence, in one-to-one correspondence with a simple class of Courant algebroids that we call constant Courant algebroids. Furthermore, we find a correspondence between certain Dirac structures and Lagrangian sub-2-groupoids. 相似文献
15.
We report a neutron scattering study of the long-wavelength dynamic spin correlations in the model two-dimensional S = 1/2 square lattice Heisenberg antiferromagnets Sr2CuO2Cl2 and Sr2Cu3O4Cl2. The characteristic energy scale, omega(0)(T/J), is determined by measuring the quasielastic peak width in the paramagnetic phase over a wide range of temperature ( 0.2 less similarT/J less similar0.7). The obtained values for omega(0)(T/J) agree quantitatively between the two compounds and also with values deduced from quantum Monte Carlo simulations. The combined data show scaling behavior, omega approximately xi(-z), over the entire temperature range with z = 1.0(1), in agreement with dynamic scaling theory. 相似文献
16.
Budelmann D Schulz B Rübhausen M Klein MV Williamsen MS Guptasarma P 《Physical review letters》2005,95(5):057003
We report on the response of the electronic continuum from inelastic light-scattering experiments over an extended energy range between 1.970 and 4.504 eV in the superconducting state of Bi2Sr2CaCu2O8. The formation of a substantial Raman feature at shifts below twice the superconducting gap as well as the additional weight above this energy are found to be strongly dependent on the incident photon energy. For excitation wavelengths observed in ultraviolet, we find an enhancement of the integrated spectral weight below T(c). The resulting composite feature shows three distinct resonances at 2.5, 3.3, and 3.8 eV. We strongly suggest that the superconductivity-induced changes are the result of both the opening of a superconducting gap and the appearance of a collective mode. 相似文献
17.
Phonon dispersion and electron-phonon coupling in MgB2 and AlB2. 总被引:2,自引:0,他引:2
We present a first principles investigation of the lattice dynamics and electron-phonon coupling of the superconductor MgB2 and the isostructural AlB2 within the framework of density functional perturbation theory using a mixed-basis pseudopotential method. Complete phonon dispersion curves and Eliashberg functions alpha2F are calculated for both systems. The main differences are related to high frequency in-plane boron vibrations, which are strongly softened in MgB2 and exhibit an exceptionally strong electron-phonon coupling. We also report on Raman measurements, which support the theoretical findings. Implications for the superconducting transition temperature are briefly discussed. 相似文献
18.
Physics of the Solid State - We studied the optical properties of the intermetallic compounds ScFe2 and ErFe2 in a wide spectral range of 0.22–15 μm. The frequency dependences of the... 相似文献
19.
We have carried out thermal expansion measurements on the heavy fermion compound URu2Si2. We have discovered a new anomaly that appears only under pressure for both the tetragonal a and c axes. Plotting these temperatures on a temperature-pressure plane, we have constructed a phase diagram, in which there is a first order phase transition boundary separating a hidden and antiferromagnetic order. When the system enters the antiferromagnetic phase from the hidden order, the lattice constant shrinks along the a axis and elongates along the c axis, leading to an increase in the lattice constant ratio of c/a. We conclude that the system lies close to a bicritical point from which the first order phase transition line emanates. 相似文献
20.
We show that a natural discretisation of Virasoro algebra yields a quantum integrable model which is the Toda chain in the second Hamiltonian structure.
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