Browsing by Author "Mou, CY"

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Explicit four-fold symmetry breaking effect on the vortex lattice in D-wave superconductors
(1998-04-01)
Chang, D
;
Mou, CY
;
Rosenstein, B
;
Wu, CL
;
電子物理學系
We use a recently developed effective Ginzberg-Landau equation to study the vortex lattice structure in d-wave superconductors. By introducing explicit four-fold symmetry breaking terms we are able to reproduce the small angle neutron scattering data on YBCO by Keimer et al. [9]. A phase diagram is also constructed and shows quite rich structures.
Instantaneous normal mode analysis of orientational motions in liquid water: Local structural effects
(2004-08-22)
Chang, SL
;
Wu, TM
;
Mou, CY
;
物理研究所
;
Institute of Physics
We have investigated the effects of local structures on the orientational motions in liquid water in terms of the instantaneous normal mode (INM) analysis. The local structures of a molecule in liquid water are characterized by two different kinds of index: the asphericity parameter of its Voronoi polyhedron and the numbers of the H bonds donated and accepted by the molecule. According to the two kinds of index, the molecules in the simulated water are classified into subensembles, for which the rotational contributions to the INM spectrum are calculated. Our results indicate that by increasing the asphericity, the rotational contribution has a shift toward the high-frequency end in the real spectrum and a decrease in the fraction of the imaginary modes. Furthermore, we find that this shift essentially relies on the number of the donated H bonds of a molecule, but has almost nothing to do with that of the accepted H bonds. The local structural effects resulting from the geometry of water molecule are also discussed. (C) 2004 American Institute of Physics.
New findings of the electromagnetic response in superconductors
(1998-04-01)
Mou, CY
;
Chang, D
;
Rosenstein, B
;
Wu, CL
;
電子物理學系
Based on the Ginzburg-Landau theory, two theoretical findings in the electromagnetic response of superconductors are described. First, we derive the most general linear response theory and then apply it to the charged super fluid regime, where the magnetic fluctuation is relevant. In particular, we show that a novel effect arises, in which the divergence of the conductivity tensor is suppressed by the diamagnetic susceptibilities. Secondly, we show that because of the approximated fourfold symmetry of the crystal lattice in high T-c cuprates, a non-vanishing Hall current can arise near Hc(2). This Hall current is non-linear and can become large to be observed if the applied electric field is large enough.
Static and dynamical anisotropy effects in the mixed state of d-wave superconductors
(1998-04-01)
Chang, D
;
Mou, CY
;
Rosenstein, B
;
Wu, CL
;
電子物理學系
We describe the effects of anisotropy caused by the crystal lattice in d-wave superconductors using an effective foe-energy approach in which only one order parameter, the d-wave order-parameter field, is used. The Abrikosov parameter beta(A) is calculated analytically for both static and moving vortex lattices. The analytic expression provides an unambiguous determination of the vortex-lattice structure. We also calculate both direct and Hall I-V curves as functions of the angle between the current and the crystal-lattice orientation. In particular, we show that near H-c2 the fourfold symmetry of the crystal lattice causes asymmetric motions of particles and holes, resulting in a nonvanishing Hall current.
The effect of anisotropy on vortex lattice structure and flux flow in d-wave superconductors
(1998-04-01)
Chang, D
;
Mou, CY
;
Rosenstein, B
;
Wu, CL
;
電子物理學系
We describe effects of anisotropy caused by the crystal lattice in d-wave superconductors using effective free energy approach in which only one order parameter, the d-wave order parameter field, is used. The Abrikosov parameter beta(A) is calculated analytically for both static and moving vortex lattices. The analytic expression provides an unambiguous determination of the vortex lattice structure. We also calculate both direct and Hall I-V curves as functions of the angle between the current and the crystal lattice orientation. In particular, we show that near H-c2 the fourfold symmetry of the crystal lattice causes asymmetric motions of particles and holes, resulting in a non-vanishing Hall current.