Hasil untuk "cond-mat.other"

Vladan Stevanovic

A python code (mvp.py) is presented for computing the mean-value point (MVP) in the Brillouin zone first introduced by Baldereschi [1]. The code allows calculations of the MVP for any input crystal structure. Having MVP allows approximating the Brillouin zone integrals of relatively smooth, periodic functions defined in the reciprocal space by the value of the same function at only one, mean-value, k-point. This approximation decreases computational cost at a relatively small decrease in accuracy. The MVP coordinates for the 14 Bravais lattices are evaluated and the underlying theory is discussed.

Nanette N. Jarenwattananon, Louis-S. Bouchard

The Carr-Purcell Meiboom-Gill (CPMG) experiment has been used for decades to measure nuclear-spin transverse ($T_2$) relaxation times. In the presence of magnetic-field inhomogeneities, the limit of short interpulse spacings yields the intrinsic $T_2$ time. Here we show that the signal decay in such experiments exhibits fundamentally different behaviors between liquids and gases. In gases, CPMG unexpectedly fails to eliminate the inhomogeneous broadening due to the non-Fickian nature of the motional averaging.

T. Storer, B. Dolezal, Matt Berenc et al.

Aleksandr Meilakhs

The new model of phonon transmission across the interface between two crystals is proposed featured by taking into account the mismatch of crystal lattices. It has been found that the mismatch of lattices results in phonon scattering at the interface even in the absence of defects. As it has been shown, at the normal incidence, longitudinally polarized phonons have much larger transmission coefficient than that of transversely polarized phonons, excluding the special resonance cases. For the quasi one-dimensional case the exact solution has been obtained.

V. L. Tsymbalenko

The internal friction in the crystals grown in two modes, namely, slow and anomalously fast (burst-like growth) modes, is measured in the temperature range 0.49-0.75K at a frequency of about 75kHz. An additional contribution to the damping decrement and softening of the dynamic modulus are detected, and their relaxation to equilibrium values at a time constant of about 3ms is observed. Possible origins of this effect are discussed.

Gennady V. Kovalev

The peak position, impact-parameter range, and optimal conditions for observing spiral scattering of relativistic particles in a uniformly bent crystal are estimated. The existence of spiral scattering with a square-root singularity is pointed out. In this case, the secondary process of volume capture to the channeling mode is absent and the conditions for observing this effect are most favorable.

C. Stuart-Andrews, V. J. Kelly, S. Sands et al.

Anh D. Phan, N. A. Viet

We have presented a detailed investigation of the Casimir interaction between the superconductor Bi2Sr2CaCu2O8+δ (BSCCO) and silicon dioxide with the presence of bromobenzene in between. We found the dispersion force is repulsive and the magnitude of the force can be changed by varying the thickness of object and temperature. The repulsive force would provide a method to deal with the stiction problems and bring much meaningful from practical views.

V. A. Nikolaenko, A. V. Smorodin

The quasi-one-dimensional system of surface electrons over superfluid helium with negative charge on substrate is investigated. The temperature dependence of conductivity is ladder-like which is observed at temperature lower 1.3 K. The parameters of ladder have been different in different experiments. The observed dependence isn't explained by classical models of carry with account to the usual scatters in channel. It is supposed the dependence have been connected with quantum character of electron transport in narrow channels.

Jia-Ning Zhang

The Abelian Higgs model is an appropriate field theoretic framework for the description of superconductivity and its topological excitations(Nielson-Olesen-Abrikosov vortex). Recently, C.-Y. Hou etl [ Phys. Rev. lett.\textbf{98} 186809 (2007)]. show that such excitations exist in graphene structures. In this paper, we show that a pseudo non-Abelian Higgs field can also be generated in graphenelike systems. Introducing a non-Abelian gauge field, we extend the chiral gauge theory for graphene constructed by R. Jackiw and S.-Y. Pi [Phys. Rev. Lett. \textbf{98}, 266402 (2007)] to the non-Abelian regime.

S. I. Burkov, O. P. Zolotova, B. P. Sorokin et al.

Anisotropy of dc electric field influence on the different types of acoustic waves in piezoelectric plate has been investigated by means of computer simulation. Detail calculations have made for bismuth germanium oxide crystals.

Abay Gadisa, Kristofer Tvingstedt, S. Admassie et al.

Wolfgang Ketterle, Martin W. Zwierlein

A review on superfluidity and the BEC-BCS crossover in ultracold Fermi gases.

Emil Lundh

Rotational states for trapped bosons in an optical lattice are studied in the framework of the Hubbard model. Critical frequencies are calculated and the main parameter regimes are identified. Transitions are observed from edge superfluids to vortex lattices with Mott insulating cores, and subsequently to lattices of interstitial vortices. The former transition coincides with the Mott transition. Changes in symmetry of the vortex lattices are observed as a function of lattice depth. Predictions for experimental signatures are presented.

J. J. Kinnunen, M. J. Holland

We study Bragg spectroscopy of a strongly interacting Bose-Einstein condensate using time-dependent Hartree-Fock-Bogoliubov theory. We include approximatively the effect of the momentum dependent scattering amplitude which is shown to be the dominant factor in determining the spectrum for large momentum Bragg scattering. The condensation of the Bragg scattered atoms is shown to significantly alter the observed excitation spectrum by creating a novel pairing channel of mobile pairs.

P. V. Ratnikov, A. P. Silin

We consider the energy spectrum of the planar quantum well which consisted of two ribbons of narrow-gap semiconductors and a graphene ribbon between ones. It is shown that the gapless mode appears only in case of inverted narrow-gap semiconductors. Spin splitting of the energy spectrum for a nonsymmetric quantum well is calculated taking into account a specificity of graphene. We investigate interface states and optical transitions. It is shown that the optical transitions are possible only with a conservation of a parity.

M. Reagan, Jonathan G. Harris, J. Tester

G. Volovik

The Kelvin-Helmholtz instability in superfluids is discussed on the basis of the first experimental observation of such an instability at the interface between superfluid 3He-A and superfluid 3He-B (R. Blaauwgeers, V. B. Eltsov, G. Eska et al., cond-mat/0111343). We discuss why the Kelvin-Helmholtz criterion, the Landau critical velocity for nucleation of ripplons, and the free-energy consideration all give different values for the instability threshold.

M. Putti, V. Braccini, E. Galleani et al.

S. Drechsler, Jiří Málek, Johannes Richter et al.

The microscopic origin of the recently observed helical structure in LiCu2O2 [1] is considered. It is shown that the frustrated antiferromagnetic double chain scenario adopted in Ref.1 is unrealistic. It should be replaced by a frustrated single-chain (CuO2) scenario proposed in Ref. 2 with ferromagnetic nearest neighbor and antiferromagnetic next nearest neighbor exchange integrals \. [1] T. Masuda et al. Phys. Rev. Lett. 92 (2004), 177201. [2] A. Gippius et al. Phys. Rev. B 70 (2004), R01426; cond-mat/0312576.