scholarly journals Possible existence of topological excitations in quantum spin models in low dimensions

1999 ◽  
Vol 60 (9) ◽  
pp. 6234-6237 ◽  
Author(s):  
Ranjan Chaudhury ◽  
Samir K. Paul
Keyword(s):  
Quantum Spin ◽  
Spin Models ◽  
Low Dimensions ◽  
Topological Excitations ◽  
Quantum Spin Models

scholarly journals Topological Excitations in Quantum Spin Systems

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Ranjan Chaudhury ◽  
Samir K. Paul
Keyword(s):  
Great Depth ◽  
Quantum Spin ◽  
Spin Fluctuations ◽  
Quantum Spin Systems ◽  
Low Dimensions ◽  
Topological Excitations ◽  
Novel Approach ◽  
Theoretical Predictions ◽  
Quantum Action ◽  
Quantum Spin Models

The origin and significance of topological excitations in quantum spin models in low dimensions are presented in detail. Besides a general review, our own work in this area is described in great depth. Apart from theoretical analysis of the existence and properties of spin vortices and antivortices, the possible experimental consequences and signatures are also highlighted. In particular, the distinguishing features between the even and odd charged topological excitations are brought out through a detailed analysis of the topological term in the quantum action. Moreover, an interesting symmetry property is predicted between the excitations from a ferromagnetic model and an antiferromagnetic model. Through a novel approach of ours, a bridge is established between field theoretical formalism and the well-known statistical mechanical treatment of Berezinskii-Kosterlitz-Thouless (BKT) transition involving these topological excitations. Furthermore, a detailed phenomenological analysis of the experimentally observed static and dynamic magnetic properties of the layered magnetic materials, possessing XY anisotropy in the in-plane spin-spin couplings, is undertaken to test the theoretical predictions regarding the behaviour of these excitations. The importance and the crucial role of quantum spin fluctuations in these studies are also brought out very clearly by our analysis.

scholarly journals THOULESS NUMBER AND SPIN DIFFUSION IN QUANTUM HEISENBERG FERROMAGNETS

1993 ◽  
Vol 07 (27) ◽  
pp. 1747-1759 ◽  
Author(s):  
PETER KOPIETZ
Keyword(s):  
Spin Diffusion ◽  
Nearest Neighbor ◽  
Arbitrary Dimension ◽  
Quantum Spin ◽  
Spin Systems ◽  
Heisenberg Ferromagnet ◽  
Electronic Systems ◽  
Dimensionless Frequency ◽  
Spin Models ◽  
Quantum Spin Models

Using an analogy between the conductivity tensor of electronic systems and the spin stiffness tensor of spin systems, we introduce the concept of the Thouless number g0 and the dimensionless frequency-dependent conductance g(ω) for quantum spin models. It is shown that spin diffusion implies the vanishing of the Drude peak of g(ω), and that the spin diffusion coefficient Ds is proportional to g0. We develop a new method based the Thouless number to calculate D s , and present results for D s in the nearest-neighbor quantum Heisenberg ferromagnet at infinite temperatures for arbitrary dimension d and spin S.

scholarly journals Exactly solvable -type quantum spin models with long-range interaction

2009 ◽  
Vol 812 (3) ◽  
pp. 402-423 ◽  
Author(s):  
B. Basu-Mallick ◽  
F. Finkel ◽  
A. González-López
Keyword(s):  
Long Range ◽  
Quantum Spin ◽  
Range Interaction ◽  
Spin Models ◽  
Exactly Solvable ◽  
Long Range Interaction ◽  
Quantum Spin Models ◽  
Solvable Type
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