Thermodynamics of a dilute XX chain in a field

Journal Article · Wed Jun 15 00:00:00 EDT 2016 · Journal of Experimental and Theoretical Physics

DOI:https://doi.org/10.1134/S1063776116060224· OSTI ID:22617244

Timonin, P. N., E-mail: [e-mail] ^[1]

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1. Southern Federal University, Physics Research Institute (Russian Federation)

Gapless phases in ground states of low-dimensional quantum spin systems are rather ubiquitous. Their peculiarity is a remarkable sensitivity to external perturbations due to permanent criticality of such phases manifested by a slow (power-low) decay of pair correlations and the divergence of the corresponding susceptibility. A strong influence of various defects on the properties of the system in such a phase can then be expected. Here, we consider the influence of vacancies on the thermodynamics of the simplest quantum model with a gapless phase, the isotropic spin-1/2 XX chain. The existence of the exact solution of this model gives a unique opportunity to describe in detail the dramatic effect of dilution on the gapless phase—the appearance of an infinite series of quantum phase transitions resulting from level crossing under the variation of a longitudinal magnetic field. We calculate the jumps in the field dependences of the ground-state longitudinal magnetization, susceptibility, entropy, and specific heat appearing at these transitions and show that they result in a highly nonlinear temperature dependence of these parameters at low T. Also, the effect of enhancement of the magnetization and longitudinal correlations in the dilute chain is established. The changes of the pair spin correlators under dilution are also analyzed. The universality of the mechanism of the quantum transition generation suggests that similar effects of dilution can also be expected in gapless phases of other low-dimensional quantum spin systems.

• OSTI ID: 22617244
• Journal Information: Journal of Experimental and Theoretical Physics, Vol. 122, Issue 6; Other Information: Copyright (c) 2016 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7761
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CORRELATIONS
CRITICALITY
DECAY
DEFECTS
DILUTION
DISTURBANCES
ENTROPY
EXACT SOLUTIONS
GROUND STATES
MAGNETIC FIELDS
MAGNETIZATION
NONLINEAR PROBLEMS
PERTURBATION THEORY
PHASE TRANSFORMATIONS
SENSITIVITY
SPECIFIC HEAT
SPIN
TEMPERATURE DEPENDENCE
THERMODYNAMICS
VACANCIES