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Šibav L, Gosar Ž, Knaflič T, Jagličić Z, King G, Nojiri H, Arčon D, Dragomir M. Higher-Magnesium-Doping Effects on the Singlet Ground State of the Shastry-Sutherland SrCu 2(BO 3) 2. Inorg Chem 2024. [PMID: 39413433 DOI: 10.1021/acs.inorgchem.4c02398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2024]
Abstract
Doping of quantum antiferromagnets is an established approach to investigate the robustness of their ground state against the competing phases. Predictions of doping effects on the ground state of the Shastry-Sutherland dimer model are here verified experimentally on Mg-doped SrCu2(BO3)2. A partial incorporation of Mg2+ on the Cu2+ site in the SrCu2(BO3)2 structure leads to a subtle but systematic lattice expansion with the increasing Mg-doping concentration, which is accompanied by a slight decrease in the spin gap, the Curie-Weiss temperature, and the peak temperature of the susceptibility. These findings indicate a doping-induced breaking of Cu2+ spin-1/2 dimers that is also corroborated by X-band EPR spectroscopy that points to a systematic increase in the intensity of free Cu2+ sites with increasing Mg-doping concentration. Extending the Mg-doping up to nominal x = 0.10 yielding SrCu1.9Mg0.1(BO3)2, in the magnetization measurements taken up to 35 T, a suppression of the pseudo-1/8 plateau is found along with a clear presence of an anomaly at an onset critical field μ0H'C0 ≈ 9 T. The latter, absent in pure SrCu2(BO3)2, emerges due to the pairwise coupling of liberated Cu2+ spin-1/2 entities in the vicinity of Mg-doping induced impurities.
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Affiliation(s)
- Lia Šibav
- Jožef Stefan Institute, Jamova cesta 39, Ljubljana 1000, Slovenia
- Jožef Stefan International Postgraduate School, Jamova cesta 39, Ljubljana 1000, Slovenia
| | - Žiga Gosar
- Jožef Stefan Institute, Jamova cesta 39, Ljubljana 1000, Slovenia
- Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, Ljubljana 1000, Slovenia
| | - Tilen Knaflič
- Jožef Stefan Institute, Jamova cesta 39, Ljubljana 1000, Slovenia
- Research Institute, Institute for the Protection of Cultural Heritage of Slovenia, Poljanska cesta 40, Ljubljana 1000, Slovenia
| | - Zvonko Jagličić
- Physics and Mechanics, Institute of Mathematics, Jadranska ulica 19, Ljubljana 1000, Slovenia
- Faculty of Civil and Geodetic Engineering, University of Ljubljana, Jamova cesta 2, Ljubljana 1000, Slovenia
| | - Graham King
- Canadian Light Source, 44 Innovation Blvd, Saskatoon, SK S7N 2V3, Canada
| | - Hiroyuki Nojiri
- Institute for Materials Research, Tohoku University, Katahira 2-1-1, Sendai 980-8577, Japan
| | - Denis Arčon
- Jožef Stefan Institute, Jamova cesta 39, Ljubljana 1000, Slovenia
- Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, Ljubljana 1000, Slovenia
| | - Mirela Dragomir
- Jožef Stefan Institute, Jamova cesta 39, Ljubljana 1000, Slovenia
- Jožef Stefan International Postgraduate School, Jamova cesta 39, Ljubljana 1000, Slovenia
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Liu WY, Zhang XT, Wang Z, Gong SS, Chen WQ, Gu ZC. Quantum Criticality with Emergent Symmetry in the Extended Shastry-Sutherland Model. PHYSICAL REVIEW LETTERS 2024; 133:026502. [PMID: 39073958 DOI: 10.1103/physrevlett.133.026502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 02/19/2024] [Accepted: 05/29/2024] [Indexed: 07/31/2024]
Abstract
Motivated by the novel phenomena observed in the layered material SrCu_{2}(BO_{3})_{2}, the Shastry-Sutherland model (SSM) has been extensively studied as the minimal model for SrCu_{2}(BO_{3})_{2}. However, the nature of its quantum phase transition from the plaquette valence-bond solid to antiferromagnetic phase is under fierce debate, posing a challenge to understand the underlying quantum criticality. Via the state-of-the-art tensor network simulations, we study the ground state of the SSM on large-scale size up to 20×20 sites. We identify the continuous transition nature accompanied by an emergent O(4) symmetry between the plaquette valence-bond solid and antiferromagnetic phase, which strongly suggests a deconfined quantum critical point (DQCP). Furthermore, we map out the phase diagram of an extended SSM that can be continuously tuned to the SSM, which demonstrates the same DQCP phenomena along a whole critical line. Our results indicate a compelling scenario for understanding the origin of the proposed proximate DQCP in recent experiments of SrCu_{2}(BO_{3})_{2}.
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Affiliation(s)
| | | | | | - Shou-Shu Gong
- School of Physical Sciences, Great Bay University, Dongguan 523000, China, and Great Bay Institute for Advanced Study, Dongguan 523000, China
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Povarov KY, Graf DE, Hauspurg A, Zherlitsyn S, Wosnitza J, Sakurai T, Ohta H, Kimura S, Nojiri H, Garlea VO, Zheludev A, Paduan-Filho A, Nicklas M, Zvyagin SA. Pressure-tuned quantum criticality in the large-D antiferromagnet DTN. Nat Commun 2024; 15:2295. [PMID: 38486067 PMCID: PMC10940708 DOI: 10.1038/s41467-024-46527-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 02/29/2024] [Indexed: 03/18/2024] Open
Abstract
Strongly correlated spin systems can be driven to quantum critical points via various routes. In particular, gapped quantum antiferromagnets can undergo phase transitions into a magnetically ordered state with applied pressure or magnetic field, acting as tuning parameters. These transitions are characterized by z = 1 or z = 2 dynamical critical exponents, determined by the linear and quadratic low-energy dispersion of spin excitations, respectively. Employing high-frequency susceptibility and ultrasound techniques, we demonstrate that the tetragonal easy-plane quantum antiferromagnet NiCl2 ⋅ 4SC(NH2)2 (aka DTN) undergoes a spin-gap closure transition at about 4.2 kbar, resulting in a pressure-induced magnetic ordering. The studies are complemented by high-pressure-electron spin-resonance measurements confirming the proposed scenario. Powder neutron diffraction measurements revealed that no lattice distortion occurs at this pressure and the high spin symmetry is preserved, establishing DTN as a perfect platform to investigate z = 1 quantum critical phenomena. The experimental observations are supported by DMRG calculations, allowing us to quantitatively describe the pressure-driven evolution of critical fields and spin-Hamiltonian parameters in DTN.
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Affiliation(s)
- Kirill Yu Povarov
- Dresden High Magnetic Field Laboratory (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany.
| | - David E Graf
- National High Magnetic Field Laboratory, Tallahassee, FL, USA
| | - Andreas Hauspurg
- Dresden High Magnetic Field Laboratory (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, Dresden, Germany
| | - Sergei Zherlitsyn
- Dresden High Magnetic Field Laboratory (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany
| | - Joachim Wosnitza
- Dresden High Magnetic Field Laboratory (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, Dresden, Germany
| | - Takahiro Sakurai
- Research Facility Center for Science and Technology, Kobe University, Kobe, Japan
| | - Hitoshi Ohta
- Molecular Photoscience Research Center, Kobe University, Kobe, Japan
- Graduate School of Science, Kobe University, Kobe, Japan
| | - Shojiro Kimura
- Institute for Materials Research, Tohoku University, Sendai, Japan
| | - Hiroyuki Nojiri
- Institute for Materials Research, Tohoku University, Sendai, Japan
| | - V Ovidiu Garlea
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | | | | | - Michael Nicklas
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
| | - Sergei A Zvyagin
- Dresden High Magnetic Field Laboratory (HLD-EMFL) and Würzburg-Dresden Cluster of Excellence ct.qmat, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany.
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Shi Z, Dissanayake S, Corboz P, Steinhardt W, Graf D, Silevitch DM, Dabkowska HA, Rosenbaum TF, Mila F, Haravifard S. Discovery of quantum phases in the Shastry-Sutherland compound SrCu 2(BO 3) 2 under extreme conditions of field and pressure. Nat Commun 2022; 13:2301. [PMID: 35484351 PMCID: PMC9050886 DOI: 10.1038/s41467-022-30036-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 04/07/2022] [Indexed: 11/22/2022] Open
Abstract
The 2-dimensional layered oxide material SrCu2(BO3)2, long studied as a realization of the Shastry-Sutherland spin topology, exhibits a range of intriguing physics as a function of both hydrostatic pressure and magnetic field, with a still debated intermediate plaquette phase appearing at approximately 20 kbar and a possible deconfined critical point at higher pressure. Here, we employ a tunnel diode oscillator (TDO) technique to probe the behavior in the combined extreme conditions of high pressure, high magnetic field, and low temperature. We reveal an extensive phase space consisting of multiple magnetic analogs of the elusive supersolid phase and a magnetization plateau. In particular, a 10 × 2 supersolid and a 1/5 plateau, identified by infinite Projected Entangled Pair States (iPEPS) calculations, are found to rely on the presence of both magnetic and non-magnetic particles in the sea of dimer singlets. These states are best understood as descendants of the full-plaquette phase, the leading candidate for the intermediate phase of SrCu2(BO3)2.
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Affiliation(s)
- Zhenzhong Shi
- Department of Physics, Duke University, Durham, NC, 27708, USA
- Institute for Advanced Study, School of Physical Science and Technology, Soochow University, Suzhou, 215006, China
| | | | - Philippe Corboz
- Institute for Theoretical Physics and Delta Institute for Theoretical Physics, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | | | - David Graf
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, 32310, USA
| | - D M Silevitch
- Division of Physics, Math and Astronomy, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Hanna A Dabkowska
- Brockhouse Institute for Material Research, McMaster University, Hamilton, ON, L8S 4M1, Canada
| | - T F Rosenbaum
- Division of Physics, Math and Astronomy, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Frédéric Mila
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Sara Haravifard
- Department of Physics, Duke University, Durham, NC, 27708, USA.
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC, 27708, USA.
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Thermodynamic, Dynamic, and Transport Properties of Quantum Spin Liquid in Herbertsmithite from an Experimental and Theoretical Point of View. CONDENSED MATTER 2019. [DOI: 10.3390/condmat4030075] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In our review, we focus on the quantum spin liquid (QSL), defining the thermodynamic, transport, and relaxation properties of geometrically frustrated magnet (insulators) represented by herbertsmithite ZnCu 3 ( OH ) 6 Cl 2 . The review mostly deals with an historical perspective of our theoretical contributions on this subject, based on the theory of fermion condensation closely related to the emergence (due to geometrical frustration) of dispersionless parts in the fermionic quasiparticle spectrum, so-called flat bands. QSL is a quantum state of matter having neither magnetic order nor gapped excitations even at zero temperature. QSL along with heavy fermion metals can form a new state of matter induced by the topological fermion condensation quantum phase transition. The observation of QSL in actual materials such as herbertsmithite is of fundamental significance both theoretically and technologically, as it could open a path to the creation of topologically protected states for quantum information processing and quantum computation. It is therefore of great importance to establish the presence of a gapless QSL state in one of the most prospective materials, herbertsmithite. In this respect, the interpretation of current theoretical and experimental studies of herbertsmithite are controversial in their implications. Based on published experimental data augmented by our theoretical analysis, we present evidence for the the existence of a QSL in the geometrically frustrated insulator herbertsmithite ZnCu 3 ( OH ) 6 Cl 2 , providing a strategy for unambiguous identification of such a state in other materials. To clarify the nature of QSL in herbertsmithite, we recommend measurements of heat transport, low-energy inelastic neutron scattering, and optical conductivity σ ¯ in ZnCu 3 ( OH ) 6 Cl 2 crystals subject to an external magnetic field at low temperatures. Our analysis of the behavior of σ ¯ in herbertsmithite justifies this set of measurements, which can provide a conclusive experimental demonstration of the nature of its spinon-composed quantum spin liquid. Theoretical study of the optical conductivity of herbertsmithite allows us to expose the physical mechanisms responsible for its temperature and magnetic field dependence. We also suggest that artificially or spontaneously introducing inhomogeneity at nanoscale into ZnCu 3 ( OH ) 6 Cl 2 can both stabilize its QSL and simplify its chemical preparation, and can provide for tests that elucidate the role of impurities. We make predictions of the results of specified measurements related to the dynamical, thermodynamic, and transport properties in the case of a gapless QSL.
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