Browsing by Author "Maniv, T."

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Chiral Anomaly and Strength of the Electron-Electron Interaction in Graphene
(2013-02-08)
Rosenstein, B.
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Lewkowicz, M.
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Maniv, T.
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電子物理學系
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Department of Electrophysics
The long-standing controversy concerning the effect of electron-electron interaction on the electrical conductivity of an ideal graphene sheet is settled. Performing the calculation directly in the tight binding approach without the usual prior reduction to the massless Dirac (Weyl) theory, it is found that, to leading order in the interaction strength alpha = e(2)/(h) over barv(0), the dc conductivity sigma/sigma(0) = 1 + C alpha + O(alpha(2)) is significantly enhanced with respect to the independent-electron result sigma(0), i.e., with the value C = 0.26. The ambiguity characterizing the various existing approaches is nontrivial and related to the chiral anomaly in the system. In order to separate the energy scales in a model with massless fermions, contributions from regions of the Brillouin zone away from the Dirac points have to be accounted for. Experimental consequences of the relatively strong interaction effect are briefly discussed. DOI: 10.1103/PhysRevLett.110.066602
Sliding Abrikosov lattice in a superconductor with a regular array of artificial pinning centers: AC conductivity and criticality at small frequencies
(2010-10-01)
Maniv, T.
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Rosenstein, B.
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Shapiro, I.
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Shapiro, B. Ya.
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Hung, R. F.
Dynamics of the flux lattice in the mixed state of strongly type-II superconductor near the upper critical field subjected to AC field and interacting with a periodic array of short range pinning centers is considered. The superconductor in a magnetic field in the absence of thermal fluctuations on is described by the time-dependent Ginzburg-Landau equations. For a special case of the delta-function shaped pinning centers and for pinning array commensurate with the Abrikosov lattice (so that vortices outnumber pinning centers) an analytic expression or the AC conductivity is obtained. It is found that below a certain critical pinning strength and for sufficiently low frequencies there exists a sliding Abrikosov lattice, which vibrates nearly uniformly despite interactions with the pinning centers. At very small frequencies the conductivity diverges at the critical pinning strength. (C) 2010 Elsevier B.V. All rights reserved.
Sliding Abrikosov vortex lattice in the presence of a regular array of columnar pinning centers: ac conductivity and criticality near the transition to a pinned state
(2009-10-01)
Maniv, T.
;
Rosenstein, B.
;
Shapiro, I.
;
Shapiro, B. Ya.
;
電子物理學系
The dynamics of the flux lattice in the mixed state of strongly type-II superconductor near the upper critical field H-c2(T) subjected to ac field and interacting with a periodic array of short-range pinning centers (nanosolid) is considered. The superconductor in a magnetic field in the absence of thermal fluctuations on the mesoscopic scale is described by the time-dependent Ginzburg-Landau equations. An exact expression for the ac resistivity in the case of a delta-function model for the pinning centers in which the nanosolid is commensurate with the Abrikosov lattice (vortices outnumber pinning centers) is obtained. It is found that below a certain critical pinning strength u(c) and sufficiently low frequencies there exists a sliding Abrikosov lattice, which moves nearly uniformly despite interactions with the pinning centers. At small frequencies the conductivity diverges as (u-u(c))(-1), whereas the ac conductivity on the depinning line diverges as i omega(-1). This sliding lattice behavior, which does not exists in the single vortex-pinning regime, becomes possible due to strong interactions between vortices when they outnumber the columnar defects. Physically it is caused by "liberation" of the temporarily trapped vortices by their freely moving neighbors.