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Zhuo Z, Li G, Shu C, Wang W, Liu C, Wu M, Huang Y, Hong M. Successive magnetic ordering in two CoII-ladder metal-organic frameworks. Sci China Chem 2020. [DOI: 10.1007/s11426-020-9842-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
Quantum Monte Carlo (QMC) methods are the gold standard for studying equilibrium properties of quantum many-body systems. However, in many interesting situations, QMC methods are faced with a sign problem, causing the severe limitation of an exponential increase in the runtime of the QMC algorithm. In this work, we develop a systematic, generally applicable, and practically feasible methodology for easing the sign problem by efficiently computable basis changes and use it to rigorously assess the sign problem. Our framework introduces measures of non-stoquasticity that-as we demonstrate analytically and numerically-at the same time provide a practically relevant and efficiently computable figure of merit for the severity of the sign problem. Complementing this pragmatic mindset, we prove that easing the sign problem in terms of those measures is generally an NP-complete task for nearest-neighbor Hamiltonians and simple basis choices by a reduction to the MAXCUT-problem.
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Affiliation(s)
- Dominik Hangleiter
- Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, Berlin, Germany
| | - Ingo Roth
- Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, Berlin, Germany
| | - Daniel Nagaj
- RCQI, Institute of Physics, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Jens Eisert
- Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, Berlin, Germany
- Helmholtz Center Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
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Jurčišinová E, Jurčišin M. Consequences of residual-entropy hierarchy violation for behavior of the specific heat capacity in frustrated magnetic systems: An exact theoretical analysis. Phys Rev E 2019; 99:042151. [PMID: 31108633 DOI: 10.1103/physreve.99.042151] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Indexed: 11/07/2022]
Abstract
We investigate in detail the influence of the violation of the strict residual-entropy hierarchy among the neighboring ground states of different orders on the low-temperature behavior of the specific heat capacity in the magnetic frustrated systems in the framework of the exactly solvable antiferromagnetic spin-1/2 Ising model with the multisite interaction in the presence of the external magnetic field on the zigzag ladder. The exact expressions for the residual entropies of all ground states of the model are found, and it is shown that when the strength of the multisite interaction is strong enough then the model exhibits a quite interesting specific situation, namely, that there exist neighboring plateau ground states together with the single-point ground state that separates them, such that the magnetization properties of all of them are different but their entropy per site is the same and equal to zero. It is shown that this fact of the violation of the strict residual-entropy hierarchy between neighboring ground states of different orders leads to the reduction of the possible number of peaks that can appear in the low-temperature behavior of the specific heat capacity in the corresponding regions of the model parametric space. In addition, it is also shown that the absence of the strict residual-entropy hierarchy among neighboring ground states of different orders changes qualitatively the behavior of the specific heat capacity as a function of the external magnetic field, namely, that the typical field-induced sharp double-peak structure in the low-temperature behavior of the specific heat capacity, which is directly related to the very existence of the highly macroscopically degenerated single-point ground states, disappears already for relatively large values of the temperature.
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Affiliation(s)
- E Jurčišinová
- Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovakia and Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141 980 Dubna, Moscow Region, Russian Federation
| | - M Jurčišin
- Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovakia and Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141 980 Dubna, Moscow Region, Russian Federation
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Cassidy SJ, Orlandi F, Manuel P, Hadermann J, Scrimshire A, Bingham PA, Clarke SJ. Complex Magnetic Ordering in the Oxide Selenide Sr 2Fe 3Se 2O 3. Inorg Chem 2018; 57:10312-10322. [PMID: 30062877 DOI: 10.1021/acs.inorgchem.8b01542] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Sr2Fe3Se2O3 is a localized-moment iron oxide selenide in which two unusual coordinations for Fe2+ ions form two sublattices in a 2:1 ratio. In the paramagnetic region at room temperature, the compound adopts the crystal structure first reported for Sr2Co3S2O3, crystallizing in space group Pbam with a = 7.8121 Å, b = 10.2375 Å, c = 3.9939 Å, and Z = 2. The sublattice occupied by two-thirds of the iron ions (Fe2 site) is formed by a network of distorted mer-[FeSe3O3] octahedra linked via shared Se2 edges and O vertices forming layers, which connect to other layers by shared Se vertices. As shown by magnetometry, neutron powder diffraction, and Mössbauer spectroscopy measurements, these moments undergo long-range magnetic ordering below TN1 = 118 K, initially adopting a magnetic structure with a propagation vector (1/2 - δ, 0, 1/2) (0 ≤ δ ≤ 0.1) which is incommensurate with the nuclear structure and described in the Pbam1 '( a01/2)000 s magnetic superspace group, until at 92 K ( TINC) there is a first order lock-in transition to a structure in which these Fe2 moments form a magnetic structure with a propagation vector (1/2, 0, 1/2) which may be modeled using a 2 a × b × 2 c expansion of the nuclear cell in space group 36.178 B a b21 m (BNS notation). Below TN2 = 52 K the remaining third of the Fe2+ moments (Fe1 site) which are in a compressed trans-[FeSe4O2] octahedral environment undergo long-range ordering, as is evident from the magnetometry, the Mössbauer spectra, and the appearance of new magnetic Bragg peaks in the neutron diffractograms. The ordering of the second set of moments on the Fe1 sites results in a slight reorientation of the majority moments on the Fe2 sites. The magnetic structure at 1.5 K is described by a 2 a × 2 b × 2 c expansion of the nuclear cell in space group 9.40 I a b (BNS notation).
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Affiliation(s)
- Simon J Cassidy
- Department of Chemistry , University of Oxford, Inorganic Chemistry Laboratory , South Parks Road , Oxford OX1 3QR , United Kingdom
| | - Fabio Orlandi
- ISIS Facility, STFC Rutherford Appleton Laboratory , Harwell Oxford , Didcot OX11 0QX , United Kingdom
| | - Pascal Manuel
- ISIS Facility, STFC Rutherford Appleton Laboratory , Harwell Oxford , Didcot OX11 0QX , United Kingdom
| | - Joke Hadermann
- Electron Microscopy for Materials Science (EMAT) , University of Antwerp , Groenenborgerlaan 171 , B-2020 Antwerp , Belgium
| | - Alex Scrimshire
- Materials and Engineering Research Institute, Faculty of Arts, Computing, Engineering and Sciences , Sheffield Hallam University, City Campus , Howard Street , Sheffield S1 1WB , United Kingdom
| | - Paul A Bingham
- Materials and Engineering Research Institute, Faculty of Arts, Computing, Engineering and Sciences , Sheffield Hallam University, City Campus , Howard Street , Sheffield S1 1WB , United Kingdom
| | - Simon J Clarke
- Department of Chemistry , University of Oxford, Inorganic Chemistry Laboratory , South Parks Road , Oxford OX1 3QR , United Kingdom
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Abstract
Small single crystals of Sr2Fe3Ch2O3 (Ch = S, Se) have been synthesized by flux methods, and bulk materials have been obtained by solid state reactions. Both compounds are isostructural to the compound Sr2Co3S2O3 (space group Pbam), which contains a novel hybrid spin ladder: a combination of a 2-leg rectangular ladder and a necklace ladder. The 2-leg ladder acts as a well-defined magnetic entity, while intimate magnetic coupling to the necklace ladder induces three successive phase transitions in the range of 40-120 K in each composition (Ch = S or Se), as revealed by Mössbauer spectroscopy, thermodynamics, and magnetometry. The complex magnetic behaviors can be explained by the unique spin-lattice topology.
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Affiliation(s)
- Kwing To Lai
- Max Planck Institute for Chemical Physics of Solids , Nöthnitzer Strasse 40, 01187 Dresden, Germany.,Department of Physics, The Chinese University of Hong Kong , Shatin, Hong Kong
| | - Peter Adler
- Max Planck Institute for Chemical Physics of Solids , Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - Yurii Prots
- Max Planck Institute for Chemical Physics of Solids , Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - Zhiwei Hu
- Max Planck Institute for Chemical Physics of Solids , Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - Chang-Yang Kuo
- Max Planck Institute for Chemical Physics of Solids , Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - Tun-Wen Pi
- National Synchrotron Radiation Research Centre , Hsinchu 30076, Taiwan
| | - Martin Valldor
- Max Planck Institute for Chemical Physics of Solids , Nöthnitzer Strasse 40, 01187 Dresden, Germany.,Leibniz Institute for Solid State and Materials Research , Helmholtz Strasse 20, 01069 Dresden, Germany
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