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.

Phase diagrams of one-, two-, and three-dimensional quantum spin systems

2016 ◽  
Vol 16 (9&10) ◽  
pp. 885-899
Author(s):  
Briiissuurs Braiorr-Orrs ◽  
Michael Weyrauch ◽  
Mykhailo V. Rakov
Keyword(s):  
Three Dimensional ◽  
Transverse Field ◽  
Quantum Spin ◽  
Three Dimensions ◽  
Quantum Spin Systems ◽  
Bipartite Entanglement ◽  
Spatial Dimensions ◽  
Characteristic Features ◽  
Quantum Spin Models ◽  
2D And 3D

We study the bipartite entanglement per bond to determine characteristic features of the phase diagram of various quantum spin models in different spatial dimensions. The bipartite entanglement is obtained from a tensor network representation of the ground state wave-function. Three spin-1/2 models (Ising, XY, XXZ, all in a transverse field) are investigated. Infinite imaginary-time evolution (iTEBD in 1D, ‘simple update’ in 2D and 3D) is used to determine the ground states of these models. The phase structure of the models is discussed for all three dimensions.

scholarly journals EFFECTIVE THEORY FOR A QUANTUM SPIN SYSTEM IN LOW DIMENSIONS – BEYOND THE LONG WAVELENGTH LIMIT

2002 ◽  
Vol 16 (08) ◽  
pp. 251-259 ◽  
Author(s):  
RANJAN CHAUDHURY ◽  
SAMIR K. PAUL
Keyword(s):  
Spin System ◽  
Quantum Spin ◽  
Effective Theory ◽  
Quantum Spin System ◽  
Partition Functions ◽  
Two Dimensional ◽  
Low Dimensions ◽  
Topological Excitations ◽  
Long Wavelength ◽  
Wavelength Limit

An effective theory for a quantum spin system in low dimensions is constructed in the finite-q regime. It is shown that there are field configurations for which Wess–Zumino terms contribute to the partition functions as topological terms for ferromagnets as well as antiferromagnets in both one- and two-dimensional lattices. This is in sharp contrast to the absence of topological excitations in two-dimensional quantum antiferromagnets in the long wavelength limit.

NOVEL PATH INTEGRAL APPROACH TO EFFECTIVE FIELD THEORIES FOR D-DIMENSIONAL QUANTUM SPIN SYSTEMS

1989 ◽  
Vol 03 (07) ◽  
pp. 1069-1083 ◽  
Author(s):  
ANTIMO ANGELUCCI ◽  
GIANCARLO JUG
Keyword(s):  
Path Integral ◽  
Effective Field ◽  
Quantum Spin ◽  
Integral Approach ◽  
Spin Liquid ◽  
Quantum Spin Systems ◽  
New Approach ◽  
Higher Temperature ◽  
Quantum Spin Models ◽  
Quantum Spin Liquid

We present a novel path integral formulation for the effective field theory describing d-dimensional quantum spin models. The new approach avoids the coherent states representation, but at very low temperatures reproduces all known results obtained with the latter technique for describing excitations of the Neél state. The possibility of exploring higher-temperature, unbroken-symmetry state excitations (such as those appropriate for the quantum spin-liquid state) within this method is illustrated.

scholarly journals Survival of itinerant excitations and quantum spin state transitions in YbMgGaO4 with chemical disorder

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
X. Rao ◽  
G. Hussain ◽  
Q. Huang ◽  
W. J. Chu ◽  
N. Li ◽  
...  
Keyword(s):  
Spin State ◽  
Magnetic Ordering ◽  
Temperature Limit ◽  
Quantum Spin ◽  
Spin Fluctuations ◽  
State Transitions ◽  
Spin Liquid ◽  
Magnetic Ground State ◽  
Effective Spin ◽  
Ideal System

AbstractA recent focus of quantum spin liquid (QSL) studies is how disorder/randomness in a QSL candidate affects its true magnetic ground state. The ultimate question is whether the QSL survives disorder or the disorder leads to a “spin-liquid-like” state, such as the proposed random-singlet (RS) state. Since disorder is a standard feature of most QSL candidates, this question represents a major challenge for QSL candidates. YbMgGaO4, a triangular lattice antiferromagnet with effective spin-1/2 Yb3+ions, is an ideal system to address this question, since it shows no long-range magnetic ordering with Mg/Ga site disorder. Despite the intensive study, it remains unresolved as to whether YbMgGaO4 is a QSL or in the RS state. Here, through ultralow-temperature thermal conductivity and magnetic torque measurements, plus specific heat and DC magnetization data, we observed a residual κ0/T term and series of quantum spin state transitions in the zero temperature limit for YbMgGaO4. These observations strongly suggest that a QSL state with itinerant excitations and quantum spin fluctuations survives disorder in YbMgGaO4.

scholarly journals Quantum Spin Systems at Positive Temperature

2006 ◽  
Vol 269 (3) ◽  
pp. 611-657 ◽  
Author(s):  
Marek Biskup ◽  
Lincoln Chayes ◽  
Shannon Starr
Keyword(s):  
Quantum Spin ◽  
Spin Systems ◽  
Positive Temperature ◽  
Quantum Spin Systems
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