Robustness of entropy plateaus: A case study of triangular Ising antiferromagnets

Bradley, Owen; Feng, Chunhan; Scalettar, Richard; Singh, Rajiv R. P.

doi:10.1103/physrevb.100.064414

Cited by 6 publications

(7 citation statements)

References 60 publications

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“…High-quality single crystals (∼ 1 cm) of TmMgGaO 4 , Tm 0.04 Lu 0.96 MgGaO 4 , and Yb 0.04 Lu 0.96 MgGaO 4 were grown by the floating zone technique (Appendix A) [11,32]. The Faraday force magnetization [33], heat capacity, magnetocaloric effect (magnetic Grüneisen ratio) [34,35] down to 30 mK were measured in a 3 He- 4 He dilution refrigerator (Appendix B). The neutron diffraction experiments were carried out in the ab plane (L = 0) and along the c axis (L = 0), on the CEA-CRG single crystal diffractometer D23 [36] of Institut Laue-Langevin (ILL) in France and on the single crystal diffractometer POLI [37] of Heinz Maier-Leibnitz Zentrum (MLZ) in Germany, respectively, down to 60 mK and up to 5 T. Using the Matlab codes, we performed CEF, exact diagonalization (ED), and spin-wave calculations for a model spin Hamiltonian.…”

Section: Technical Detailsmentioning

confidence: 99%

“…Geometrical frustration can render the ground state(s) of the correlated spin system macroscopically degenerate and completely disordered in the classical Ising case [1][2][3][4][5][6], or trigger strong quantum fluctuations that prevent the conventional symmetry breaking even down to ∼ 0 K in the quantum case [7][8][9][10][11][12][13][14][15]. In most of the previously proposed frustrated magnets, the (effective) S = 1/2 dipole moments of the ground-state (GS) doublets are protected either by time-reversal symmetry in the case of Kramers ions with an odd number of electrons per site [4,[12][13][14][15][16] or by the local crystal electric field (CEF) symmetry in the case of non-Kramers ions with an even number of electrons per site [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

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Partial Up-Up-Down Order with the Continuously Distributed Order Parameter in the Triangular Antiferromagnet TmMgGaO4

Bachus

Deng

et al. 2020

Phys. Rev. X

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Frustrated quasidoublets without time-reversal symmetry can host highly unconventional magnetic structures with continuously distributed order parameters even in a single-phase crystal. Here, we report the comprehensive thermodynamic and neutron diffraction investigation on the single crystal of TmMgGaO4, which entails non-Kramers Tm 3+ ions arranged on a geometrically perfect triangular lattice. The crystal electric field (CEF) randomness caused by the site-mixing disorder of the nonmagnetic Mg 2+ and Ga 3+ ions, merges two lowest-lying CEF singlets of Tm 3+ into a ground-state (GS) quasidoublet. Well below Tc ∼ 0.7 K, a small fraction of the antiferromagnetically coupled Tm 3+ Ising quasidoublets with small inner gaps condense into two-dimensional (2D) up-up-down magnetic structures with continuously distributed order parameters, and give rise to the columnar magnetic neutron reflections below µ0Hc ∼ 2.6 T, with highly anisotropic correlation lengths, ξ ab ≥ 250a in the triangular plane and ξc < c/12 between the planes. The remaining fraction of the Tm 3+ ions remain nonmagnetic at 0 T and become uniformly polarized by the applied longitudinal field at low temperatures. We argue that the similar model can be generally applied to other compounds of non-Kramers rare-earth ions with correlated GS quasidoublets.

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Section: Technical Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Partial Up-Up-Down Order with the Continuously Distributed Order Parameter in the Triangular Antiferromagnet TmMgGaO4

Bachus

Deng

et al. 2020

Phys. Rev. X

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“…Residual entropy plateaus at intermediate temperatures are a generic feature of highly frustrated systems including the Kitaev systems and their experimental realizations [27,[37][38][39][40][41][42][43]. These represent a classical spin-liquid state [1], with a highly degenerate manifold of configurations, which is a precursor to the quantum selection that leads to the quantum spin-liquid at still lower temperatures.…”

Section: Discussionmentioning

confidence: 99%

Thermodynamic behavior of modified integer-spin Kitaev models on the honeycomb lattice

et al. 2021

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We study the thermodynamic behavior of modified spin-S Kitaev models introduced by Baskaran, Sen, and Shankar [Phys. Rev. B 78, 115116 (2008)]. These models have the property that for half-odd-integer spins their eigenstates map on to those of spin-1/2 Kitaev models, with well-known highly entangled quantum spin-liquid states and Majorana fermions. For integer spins, the Hamiltonian is made out of commuting local operators. Thus, the eigenstates can be chosen to be completely unentangled between different sites, though with a significant degeneracy for each eigenstate. For half-odd-integer spins, the thermodynamic properties can be related to the spin-1/2 Kitaev models apart from an additional degeneracy. Hence we focus here on the case of integer spins. We use transfer matrix methods, high-temperature expansions, and Monte Carlo simulations to study the thermodynamic properties of ferromagnetic and antiferromagnetic models with spin S = 1 and S = 2. Apart from large residual entropies, which all the models have, we find that they can have a variety of different behaviors. Transfer matrix calculations show that for the different models, the correlation lengths can be finite as T → 0, become critical as T → 0, or diverge exponentially as T → 0. The Z 2 flux variable associated with each hexagonal plaquette saturates at the value +1 as T → 0 in all models except the S = 1 antiferromagnet where the mean flux remains zero as T → 0. We provide qualitative explanations for these results.

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“…Residual entropy plateaus at intermediate temperatures are a generic feature of highly frustrated systems including the Kitaev systems and their experimental re- alizations [35][36][37][38][39][40][41][42]. These represent a classical spin-liquid state [1], with a highly degenerate manifold of configurations, which is a precursor to the quantum selection that leads to the quantum spin-liquid at still lower temperatures.…”

Section: Discussionmentioning

confidence: 99%

Thermodynamic behavior of modified integer-spin Kitaev models on the honeycomb lattice

Bradley,

Oitmaa,

Sen

et al. 2020

Preprint

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We study the thermodynamic properties of modified spin-S Kitaev models introduced by Baskaran, Sen and Shankar (Phys. Rev. B 78, 115116 (2008)). These models have the property that for half-odd-integer spins their eigenstates map on to those of spin-1/2 Kitaev models, with well-known highly entangled quantum spin-liquid states and Majorana fermions. For integer spins, the Hamiltonian is made out of commuting local operators. Thus, the eigenstates can be chosen to be completely unentangled between different sites, though with a significant degeneracy for each eigenstate. For half-odd-integer spins, the thermodynamic properties can be related to the spin-1/2 Kitaev models apart from an additional degeneracy. Hence we focus here on the case of integer spins. We use transfer matrix methods, high temperature expansions and Monte Carlo simulations to study the thermodynamic properties of ferromagnetic and antiferromagnetic models with spin S = 1 and S = 2. Apart from large residual entropies, which all the models have, we find that they can have a variety of different behaviors. Transfer matrix calculations show that for the different models, the correlation lengths can be finite as T → 0, become critical as T → 0 or diverge exponentially as T → 0. There is a conserved Z2 flux variable associated with each hexagonal plaquette which saturates at the value +1 as T → 0 in all models except the S = 1 antiferromagnet where the mean flux remains zero as T → 0. We provide qualitative explanations for these results.

show abstract

Robustness of entropy plateaus: A case study of triangular Ising antiferromagnets

Cited by 6 publications

References 60 publications

Partial Up-Up-Down Order with the Continuously Distributed Order Parameter in the Triangular Antiferromagnet TmMgGaO4

Partial Up-Up-Down Order with the Continuously Distributed Order Parameter in the Triangular Antiferromagnet TmMgGaO4

Thermodynamic behavior of modified integer-spin Kitaev models on the honeycomb lattice

Thermodynamic behavior of modified integer-spin Kitaev models on the honeycomb lattice

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