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Quantum and Low-Dimensional Magnetism

Magnetism of condensed matter systems is a fundamentally quantum phenomenon - it originates from the  Pauli principle governing electron's behavior and was only explained with the advent of quantum mechanics. Nevertheless, many properties of common magnetic materials whose magnetism mainly arises from magnetization associated with total spin angular momentum (quantum number) of atomic electrons, which is large compared to ħ, can be understood on the (semi)classical level, neglecting quantum fluctuations. 

The situation is dramatically different in magnets where spins are small, ħS = ħ/2 or ħS = ħ, and interactions are quasi one- or two- dimensional (1D or 2D). In the ideal case, where spin coupling is strictly 1D, spin system with spin-isotropic interactions never orders, even at T=0, while in 2D magnetic order disappears at any finite temperature. This is a well-known Mermin-Wagner theorem, which extends to magnets a similar statement due to Peierls and Landau on the instability of low-dimensional crystals. When they order due to residual 3D and/or anisotropic interactions, magnets with small spins, like crystals made of light atoms, exhibit quantum-crystalline phases with weak order and large zero-point motion.

Our current research topics include:

 

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Last Modified: Friday, 21-Mar-2008 18:22:59 EDT
Please forward all questions about this site to: Igor Zaliznyak

 

:: News :: Announcements ::

"Hidden Order Found in a Quantum Spin Liquid" by G. Xu et al.; read about it in Science Magazine: Abstract, Full Text (PDF).

"Quasiparticle Behavior In Bose Quantum Liquids - Discovering the failure point of certain quasiparticles may help to understand unusual behavior of many useful materials" - read Brookhaven Bulletin article on Igor Zaliznyak's work here or Nature (2006) or cond-mat/0511266

Gen Shirane: Accomplishments and Reminiscences

"Quantum magnetic excitations from stripes in copper oxide superconductors," Tranquada et al.,
  Nature (2004)  or cond-mat/0401621