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Michael Stone

Publications and source records attributed to Michael Stone.

61 records · Page 4Linked to original sources
arXiv1995

The Magnus Force on Skyrmions in Ferromagnets and the Quantum Hall Effect

The topological solitons, or ``skyrmions'', in a planar ferromagnet experience a Magnus force proportional to the product of their velocity and the surrounding magnetization. It has been suggested that the charged quasiparticles near filling factor $ν=1$ in the $GaAs$ quantum Hall effect are skyrmions. If so we might expect this spin-induced Magnus force to act on the quasiparticles in addition to the Lorentz force they experience because of their charge. We show that this is not the case, and that the Magnus and Lorentz forces are merely different descriptions of the same physical effect.

cond-mat↗
arXiv1995

Josephson Current and Proximity Effect in Luttinger Liquids

A theory describing a one-dimensional Luttinger liquid in contact with superconductor is developed. Boundary conditions for the fermion fields describing Andreev reflection at the contacts are derived and used to construct a bosonic representation of the fermions. The Josephson current through a superconductor/Luttinger liquid/superconductor junction is considered for both perfectly and poorly transmitting interfaces. In the former case, the Josephson current at low temperatures is found to be essentially unaffected by electron-electron interactions. In the latter case, significant renormalization of the Josephson current occurs. The profile of the (induced) condensate wavefunction in a semi-infinite Luttinger liquid in contact with a superconductor is shown to decay as a power-law, the exponent depending on the sign and strength of the interactions. In the case of repulsive (attractive) interactions the decay is faster (slower) than in their absence. An equivalent method of calculating the Josephson current through a Luttinger liquid, which employs the bosonization of the system as a whole (i.e., superconductor, as well as Luttinger liquid) is developed and shown to give the results equivalent to those obtained via boundary conditions describing Andreev reflection.

cond-mat↗
arXiv1995

"Classical" Vortex Nucleation in Superflow Through Small Orifices

We report on numerical solutions of the Gross-Pitaevskii equation for two-dimensional flow of a superfluid condensate through a small orifice. Above a critical velocity of about $30\%$ of the speed of sound, cavitation occurs in the throat of the orifice. The cavitating bubbles form the cores of singly quantized vortices which detach from the boundary and are convected downstream.

cond-mat↗
arXiv1995

Landauer Conductance of Luttinger Liquids with Leads

We show that the dc conductance of a quantum wire containing a Luttinger liquid and attached to non-interacting leads is given by $e^2/h$ per spin orientation, regardless of the interactions in the wire. This explains the recent observations of the absence of conductance renormalization in long high-mobility $GaAs$ wires by Tarucha, Honda and Saku (Solid State Communications {\bf 94}, 413 (1995)).

cond-mat↗
arXiv1994

Dynamics of T=0 BCS condensates

Fermi-surface bosonization is used to show that the long-wavelength, $T=0$, dynamics of a BCS superfluid or superconductor is described by a galilean invariant non-linear time-dependent Schr{ö}dinger equation. This equation is of same form as the Gross-Pitaevskii equation for a Bose superfluid, but the ``wavefunction'' is {\it not} the superfluid order parameter.

cond-mat↗
arXiv1993

Propogation of Electromagnetic Waves in the Core of a String Defect in Liquid Crystals

We investigate the propagation of electromagnetic waves in the core of a winding number one string defect with isotropic core in nematic liquid crystals. We numerically solve wave equations for the TE mode and show the existence of guided modes arising due to the variation of the refractive index as a function of the scalar order parameter.

cond-mat↗