https://doi.org/10.1140/epjb/s10051-023-00566-3
Regular Article - Statistical and Nonlinear Physics
End-point singularity of the XY-paramagnetic phase boundary for the 
D 
square-lattice 
–
XY model with the single-ion anisotropy
Department of Physics, Faculty of Science, Okayama University, 700-8530, Okayama, Japan
a
nisiyama@science.okayama-u.ac.jp
Received:
23
July
2022
Accepted:
3
July
2023
Published online:
12
July
2023
The two-dimensional quantum-spin square-lattice –XY model with the single-ion anisotropy D was investigated numerically, placing an emphasis on the end-point singularity of the phase boundary separating the XY and paramagnetic phases in proximity to the fully frustrated point, 
. We employed the exact diagonalization method to circumvent the negative sign problem of the quantum Monte Carlo method, and evaluated the fidelity susceptibility 
as a probe to detect the phase transition. As a preliminary survey, for an intermediate value of 
, the D-driven XY-paramagnetic phase transition was investigated via the probe . It turned out that the criticality belongs to the 3D-XY universality class. Thereby, the data were cast into the crossover-scaling formula with the properly scaled distance from the multi-critical point, 
. The set of multi-critical indices was obtained, and compared to those of the quantum Lifshitz criticality.
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© The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature 2023. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
