57 research outputs found
Superconducting fluctuation corrections to ultrasound attenuation in layered superconductors
We consider the temperature dependence of the sound attenuation and sound
velocity in layered impure metals due to superconducting fluctuations of the
order parameter above the critical temperature. We obtain the dependence on
material properties of these fluctuation corrections in the hydrodynamic limit,
where the electron mean free path is much smaller than the wavelength of sound
and where the electron collision rate is much larger than the sound frequency.
For longitudinal sound propagating perpendicular to the layers, the open Fermi
surface condition leads to a suppression of the divergent contributions to
leading order, in contrast with the case of paraconductivity. The leading
temperature dependent corrections, given by the Aslamazov-Larkin, Maki-Thompson
and density of states terms, remain finite as T->Tc. Nevertheless, the
sensitivity of new ultrasonic experiments on layered organic conductors should
make these fluctuations effects measurable.Comment: 13 pages, 6 figures. Accepted for PRB. Added discussion on incoherent
interlayer tunneling and other small modifications suggested by referee
Antiferromagnetic Domains and Superconductivity in UPt3
We explore the response of an unconventional superconductor to spatially
inhomogeneous antiferromagnetism (SIAFM). Symmetry allows the superconducting
order parameter in the E-representation models for UPt3 to couple directly to
the AFM order parameter. The Ginzburg-Landau equations for coupled
superconductivity and SIAFM are solved numerically for two possible SIAFM
configurations: (I) abutting antiferromagnetic domains of uniform size, and
(II) quenched random disorder of `nanodomains' in a uniform AFM background. We
discuss the contributions to the free energy, specific heat, and order
parameter for these models. Neither model provides a satisfactory account of
experiment, but results from the two models differ significantly. Our results
demonstrate that the response of an E_{2u} superconductor to SIAFM is strongly
dependent on the spatial dependence of AFM order; no conclusion can be drawn
regarding the compatibility of E_{2u} superconductivity with UPt3 that is
independent of assumptions on the spatial dependence of AFMComment: 12 pages, 13 figures, to appear in Phys. Rev.
Meeting deadlines in work groups: Implicit and explicit mechanisms
Nous nous sommes demandĂ©s, dans cette Ă©tude, si les groupes Ă©taient mieux Ă mĂȘme de respecter les dĂ©lais quand leurs membres partageaient les mĂȘmes cognitions temporelles, câest-Ă -dire quand ils sâaccordaient sur les dimensions temporelles de leur tĂąche. Dans une Ă©tude longitudinale portant sur 31 groupes, nous avons Ă©tudiĂ© lâeffet des cognitions temporelles partagĂ©es sur le respect dâun dĂ©lai et explorĂ© deux antĂ©cĂ©dents des cognitions temporelles partagĂ©es: la cohĂ©rence des rythmes des membres du groupe et lâĂ©change des rappels concernant le temps. Nos rĂ©sultats montrent que ces deux facteurs ont un impact sur les cognitions temporelles partagĂ©es et cela Ă diffĂ©rentes Ă©tapes du travail collectif. De plus, il est apparu que les cognitions temporelles partagĂ©es pouvaient aussi bien faciliter que contrecarrer le respect des dĂ©lais: cela dĂ©pend des rythmes des membres du groupe. In this study, we examined whether groups were better able to meet deadlines when group members had shared temporal cognitions, that is, when they agreed on the temporal aspects of their task. In a longitudinal study involving 31 groups, we studied the effect of shared temporal cognitions on meeting a deadline and explored two antecedents of shared temporal cognitions: the similarity in group membersâ pacing styles and the exchange of temporal reminders. Our findings suggest that both antecedents are relevant to shared temporal cognitions, be it at different stages of group collaboration. Furthermore, we found that shared temporal cognitions may either facilitate or impede meeting a deadline, depending on the content of group membersâ pacing styles
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