Title:	Classical Langevin dynamics of a charged particle moving on a sphere and diamagnetism: a surprise
Authors:	Kumar, N. Kumar, K.V.
Keywords:	Diamagnetism, paramagnetism, and superparamagnetism Fluctuation phenomena, random processes, noise, and Brownian motion Electron gas, Fermi gas
Issue Date:	Apr-2009
Publisher:	EDP Sciences / IOP / Società Italiana di Fisica
Citation:	Europhysics Letters, 2009, Vol.86, 17001
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.
Description:	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI:	http://hdl.handle.net/2289/3800
ISSN:	E-ISSN: 1286-4854 P-ISSN: 0295-5075
Alternative Location:	http://arxiv.org/abs/0811.3071 http://dx.doi.org/10.1209/0295-5075/86/17001
Copyright:	2009 EPLA
Appears in Collections:	Research Papers (TP)

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