Sumedha, ; Barma, Mustansir (2022) Solution of the random field XY magnet on a fully connected graph Journal of Physics A: Mathematical and Theoretical, 55 (9). 095001. ISSN 1751-8113
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Official URL: http://doi.org/10.1088/1751-8121/ac4b8b
Related URL: http://dx.doi.org/10.1088/1751-8121/ac4b8b
Abstract
We use large deviation theory to obtain the free energy of the XY model on a fully connected graph on each site of which there is a randomly oriented field of magnitude h. The phase diagram is obtained for two symmetric distributions of the random orientations: (a) a uniform distribution and (b) a distribution with cubic symmetry. In both cases, the disorder–averaged ordered state reflects the symmetry of the underlying distribution. The phase boundary has a multicritical point (MCP) which separates a locus of continuous transitions (for small values of h) from a locus of first order transitions (for large h). The free energy is a function of a single variable in case (a) and a function of two variables in case (b), leading to different characters of the MCPs in the two cases. We find that the locus of continuous transitions is given by the same equation for a family of quadriperiodic distributions, which includes the distributions (a) and (b). However, the location of the MCP and the nature of ordered state depend on the form of the distribution. The disorder-averaged ground state energy is found exactly, and the specific heat is shown to approach a constant as temperature approaches zero.
Item Type: | Article |
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Source: | Copyright of this article belongs to Institute of Physics Publishing. |
ID Code: | 129749 |
Deposited On: | 02 Dec 2022 06:09 |
Last Modified: | 06 Dec 2022 10:39 |
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