150638 20251017144557.0 doi 10.1103/PhysRevB.111.014425 sideral 142786 ART-2025-142786 eng Herráiz-López, Víctor Universidad de Zaragoza (orcid)0009-0007-8481-0981 First- and second-order quantum phase transitions in the long-range unfrustrated antiferromagnetic Ising chain 2025 Access copy available to the general public Unrestricted We study the ground-state phase diagram of an unfrustrated antiferromagnetic Ising chain with longitudinal and transverse fields in the full range of interactions: from all-to-all to nearest-neighbors. First, we solve the model analytically in the strong long-range regime, confirming in the process that a mean-field treatment is exact for this model. We compute the order parameter and the correlations and show that the model exhibits a tricritical point where the phase transition changes from first to second order. This is in contrast with the nearest-neighbor limit where the phase transition is known to be second order. To understand how the order of the phase transition changes from one limit to the other, we tackle the analytically intractable interaction ranges numerically, using a variational quantum Monte Carlo method with a neural-network-based ansatz, the visual transformer. We show how the first-order phase transition shrinks with decreasing interaction range and establish approximate boundaries in the interaction range for which the first-order phase transition is present. Finally, we establish that the key ingredient to stabilize a first-order phase transition and a tricritical point is the presence of ferromagnetic interactions between spins of the same sublattice on top of antiferromagnetic interactions between spins of different sublattices. Tunable-range unfrustrated antiferromagnetic interactions are just one way to implement such staggered interactions. info:eu-repo/grantAgreement/ES/AEI/CEX2023-001286-S info:eu-repo/grantAgreement/ES/DGA/E09-17R-Q-MAD info:eu-repo/grantAgreement/ES/MCIU/FPU20-07231 info:eu-repo/grantAgreement/EUR/MICINN/TED2021-131447B-C21 info:eu-repo/semantics/openAccess All rights reserved http://www.europeana.eu/rights/rr-f/ info:eu-repo/semantics/article info:eu-repo/semantics/acceptedVersion Roca-Jerat, Sebastián Gallego, Manuel Universidad de Zaragoza Ferrández, Ramón Universidad de Zaragoza (orcid)0000-0001-8782-1335 Carrete, Jesús (orcid)0000-0003-0971-1098 Zueco, David (orcid)0000-0003-4478-1948 Román-Roche, Juan Universidad de Zaragoza (orcid)0000-0003-2995-6615 2002 385 Universidad de Zaragoza Dpto. Física Aplicada Área Física Aplicada 2004 405 Universidad de Zaragoza Dpto. Física Teórica Área Física Teórica 1009 617 Universidad de Zaragoza Dpto. Patología Animal Área Medicina y Cirugía Animal 111, 1 (2025), 014425 [14 pp.] Phys. Rev. B Physical Review B 2469-9950 929345 http://zaguan.unizar.es/record/150638/files/texto_completo.pdf Postprint 2735454 http://zaguan.unizar.es/record/150638/files/texto_completo.jpg?subformat=icon icon Postprint oai:zaguan.unizar.es:150638 articulos driver 2025-10-17-14:13:38 ARTICLE