Classical Langevin dynamics of a charged particle moving on a sphere and diamagnetism: A surprise

Kumar, N and Kumar, K Vijay (2009) Classical Langevin dynamics of a charged particle moving on a sphere and diamagnetism: A surprise. In: Europhysics Letters, 86 (1). 17001-p1.

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Abstract

It is generally known that the orbital diamagnetism of a classical system of charged particles in thermal equilibrium is identically zero —the Bohr-van Leeuwen theorem. Physically, this null result derives from the exact cancellation of the orbital diamagnetic moment associated with the complete cyclotron orbits of the charged particles by the paramagnetic moment subtended by the incomplete orbits skipping the boundary in the opposite sense. Motivated by this crucial but subtle role of the boundary, we have simulated here the case of a finite but unbounded system, namely that of a charged particle moving on the surface of a sphere in the presence of an externally applied uniform magnetic field. Following a real space-time approach based on the classical Langevin equation, we have computed the orbital magnetic moment that now indeed turns out to be non-zero and has the diamagnetic sign. To the best of our knowledge, this is the first report of the possibility of finite classical diamagnetism in principle, and it is due to the avoided cancellation.

Item Type:	Journal Article
Publication:	Europhysics Letters
Publisher:	EDP Sciences
Additional Information:	Copyright of this article belongs to EDP Sciences.
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	02 Jul 2009 12:02
Last Modified:	19 Sep 2010 05:34
URI:	http://eprints.iisc.ac.in/id/eprint/20734

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