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Two-dimensional quantum universality in the spin-1/2 triangular-lattice quantum antiferromagnet Na 2BaCo(PO 4) 2. Proc Natl Acad Sci U S A 2022; 119:e2211193119. [PMID: 36520670 PMCID: PMC9907114 DOI: 10.1073/pnas.2211193119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
An interplay of geometrical frustration and strong quantum fluctuations in a spin-1/2 triangular-lattice antiferromagnet (TAF) can lead to exotic quantum states. Here, we report the neutron-scattering, magnetization, specific heat, and magnetocaloric studies of the recently discovered spin-1/2 TAF Na2BaCo(PO4)2, which can be described by a spin-1/2 easy axis XXZ model. The zero-field neutron diffraction experiment reveals an incommensurate antiferromagnetic ground state with a significantly reduced ordered moment of about 0.54(2) μB/Co. Different magnetic phase diagrams with magnetic fields in the ab plane and along the easy c-axis were extracted based on the magnetic susceptibility, specific heat, and elastic neutron-scattering results. In addition, two-dimensional (2D) spin dispersion in the triangular plane was observed in the high-field polarized state, and microscopic exchange parameters of the spin Hamiltonian have been determined through the linear spin wave theory. Consistently, quantum critical behaviors with the universality class of d = 2 and νz = 1 were established in the vicinity of the saturation field, where a Bose-Einstein condensation (BEC) of diluted magnons occurs. The newly discovered quantum criticality and fractional magnetization phase in this ideal spin-1/2 TAF present exciting opportunities for exploring exotic quantum phenomena.
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Wu LS, Nikitin SE, Wang Z, Zhu W, Batista CD, Tsvelik AM, Samarakoon AM, Tennant DA, Brando M, Vasylechko L, Frontzek M, Savici AT, Sala G, Ehlers G, Christianson AD, Lumsden MD, Podlesnyak A. Tomonaga-Luttinger liquid behavior and spinon confinement in YbAlO 3. Nat Commun 2019; 10:698. [PMID: 30741939 PMCID: PMC6370837 DOI: 10.1038/s41467-019-08485-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 01/14/2019] [Indexed: 11/09/2022] Open
Abstract
Low dimensional quantum magnets are interesting because of the emerging collective behavior arising from strong quantum fluctuations. The one-dimensional (1D) S = 1/2 Heisenberg antiferromagnet is a paradigmatic example, whose low-energy excitations, known as spinons, carry fractional spin S = 1/2. These fractional modes can be reconfined by the application of a staggered magnetic field. Even though considerable progress has been made in the theoretical understanding of such magnets, experimental realizations of this low-dimensional physics are relatively rare. This is particularly true for rare-earth-based magnets because of the large effective spin anisotropy induced by the combination of strong spin-orbit coupling and crystal field splitting. Here, we demonstrate that the rare-earth perovskite YbAlO3 provides a realization of a quantum spin S = 1/2 chain material exhibiting both quantum critical Tomonaga-Luttinger liquid behavior and spinon confinement-deconfinement transitions in different regions of magnetic field-temperature phase diagram.
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Affiliation(s)
- L S Wu
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
- Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China.
| | - S E Nikitin
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187, Dresden, Germany
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01069, Dresden, Germany
| | - Z Wang
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, 37996, USA
| | - W Zhu
- Westlake Institute of Advanced Study, 310024, Hangzhou, P. R. China
- Theoretical Division, T-4 and CNLS, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - C D Batista
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN, 37996, USA
- Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - A M Tsvelik
- Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - A M Samarakoon
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - D A Tennant
- Shull-Wollan Center, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - M Brando
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187, Dresden, Germany
| | - L Vasylechko
- Lviv Polytechnic National University, Lviv, 79013, Ukraine
| | - M Frontzek
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - A T Savici
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - G Sala
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - G Ehlers
- Neutron Technologies Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - A D Christianson
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - M D Lumsden
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - A Podlesnyak
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
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Varma CM. Quantum-critical fluctuations in 2D metals: strange metals and superconductivity in antiferromagnets and in cuprates. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:082501. [PMID: 27411298 DOI: 10.1088/0034-4885/79/8/082501] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The anomalous transport and thermodynamic properties in the quantum-critical region, in the cuprates, and in the quasi-two dimensional Fe-based superconductors and heavy-fermion compounds, have the same temperature dependences. This can occur only if, despite their vast microscopic differences, a common statistical mechanical model describes their phase transitions. The antiferromagnetic (AFM)-ic models for the latter two, just as the loop-current model for the cuprates, map to the dissipative XY model. The solution of this model in (2+1)D reveals that the critical fluctuations are determined by topological excitations, vortices and a variety of instantons, and not by renormalized spin-wave theories of the Landau-Ginzburg-Wilson type, adapted by Moriya, Hertz and others for quantum-criticality. The absorptive part of the fluctuations is a separable function of momentum [Formula: see text], measured from the ordering vector, and of the frequency ω and the temperature T which scale as [Formula: see text] at criticality. Direct measurements of the fluctuations by neutron scattering in the quasi-two-dimensional heavy fermion and Fe-based compounds, near their antiferromagnetic quantum critical point, are consistent with this form. Such fluctuations, together with the vertex coupling them to fermions, lead to a marginal fermi-liquid, with the imaginary part of the self-energy [Formula: see text] for all momenta, a resistivity [Formula: see text], a [Formula: see text] contribution to the specific heat, and other singular fermi-liquid properties common to these diverse compounds, as well as to d-wave superconductivity. This is explicitly verified, in the cuprates, by analysis of the pairing and the normal self-energy directly extracted from the recent high resolution angle resolved photoemission measurements. This reveals, in agreement with the theory, that the frequency dependence of the attractive irreducible particle-particle vertex in the d-wave channel is the same as the irreducible particle-hole vertex in the full symmetry of the lattice.
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Affiliation(s)
- Chandra M Varma
- Department of Physics and Astronomy, University of California, Riverside, CA 92521, USA
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Sales BC, Jin K, Bei H, Stocks GM, Samolyuk GD, May AF, McGuire MA. Quantum Critical Behavior in a Concentrated Ternary Solid Solution. Sci Rep 2016; 6:26179. [PMID: 27188715 PMCID: PMC4870641 DOI: 10.1038/srep26179] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 04/27/2016] [Indexed: 11/11/2022] Open
Abstract
The face centered cubic (fcc) alloy NiCoCrx with x ≈ 1 is found to be close to the Cr concentration where the ferromagnetic transition temperature, Tc, goes to 0. Near this composition these alloys exhibit a resistivity linear in temperature to 2 K, a linear magnetoresistance, an excess –TlnT (or power law) contribution to the low temperature heat capacity, and excess low temperature entropy. All of the low temperature electrical, magnetic and thermodynamic properties of the alloys with compositions near x ≈ 1 are not typical of a Fermi liquid and suggest strong magnetic fluctuations associated with a quantum critical region. The limit of extreme chemical disorder in this simple fcc material thus provides a novel and unique platform to study quantum critical behavior in a highly tunable system.
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Affiliation(s)
- Brian C Sales
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA 37831-6056
| | - Ke Jin
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA 37831-6056
| | - Hongbin Bei
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA 37831-6056
| | - G Malcolm Stocks
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA 37831-6056
| | - German D Samolyuk
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA 37831-6056
| | - Andrew F May
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA 37831-6056
| | - Michael A McGuire
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA 37831-6056
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Peratheepan P, Strydom AM. Electronic, magnetic, and transport properties of the isotypic aluminides SmT₂Al₁₀ (T = Fe, Ru). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:095604. [PMID: 25690044 DOI: 10.1088/0953-8984/27/9/095604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report the results of a comprehensive physical and magnetic property study of the new isotypic aluminides SmT₂Al₁₀ (T = Fe, Ru). These two compounds are members of a rare-earth based system which has become an exemplary case study of the interplay of magnetism and correlated electron phenomena. SmFe₂Al₁₀ and SmRu₂Al₁₀ are found to order in a putative antiferromagnetic spin arrangement at T(N) = 14.5 K and 12.5 K, respectively. Moreover, SmRu₂Al₁₀ shows a further phase transition at T(SR) = 5 K which is likely due to spin reorientation. The susceptibility of SmFe₂Al₁₀ points to a valence instability of the Sm ionic state at intermediate temperatures well above T(N). Electronic and thermal transport confirm that SmFe₂Al₁₀ undergoes an antiferromagnetic superzone gap formation below T(N), whereas SmRu₂Al₁₀ suffers a lattice anomaly driven magnetoelastic coupling at T(N). Below T(N), the physical properties of SmT₂Al₁₀ (T = Fe, Ru) are governed by magnons with an antiferromagnetic spin-wave spectrum that reveals spin-gap opening. Our findings in this work have exposed a new anomalous correlated compound in the RT₂Al₁₀ series. SmFe₂Al₁₀ has a magnetic ordered ground state in spite of an unstable valence at higher temperature. This is comparable with CeRu₂Al₁₀, which is a unique and controversial Kondo insulator that orders antiferromagnetic at T(N) = 27 K. Among the series of rare-earth RT₂Al₁₀ compounds, the presented Sm compounds are two new members with anomalously high magnetic ordering temperatures, and it is envisaged that together with the two very well studied compounds CeRu₂Al₁₀ and CeOs₂Al₁₀ our presented studies will enable a broader approach towards understanding the fascinating properties of this materials class.
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