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Lu L, Song M, Liu W, Reyes AP, Kuhns P, Lee HO, Fisher IR, Mitrović VF. Magnetism and local symmetry breaking in a Mott insulator with strong spin orbit interactions. Nat Commun 2017; 8:14407. [PMID: 28181502 PMCID: PMC5309813 DOI: 10.1038/ncomms14407] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 12/25/2016] [Indexed: 11/09/2022] Open
Abstract
Study of the combined effects of strong electronic correlations with spin-orbit coupling (SOC) represents a central issue in quantum materials research. Predicting emergent properties represents a huge theoretical problem since the presence of SOC implies that the spin is not a good quantum number. Existing theories propose the emergence of a multitude of exotic quantum phases, distinguishable by either local point symmetry breaking or local spin expectation values, even in materials with simple cubic crystal structure such as Ba2NaOsO6. Experimental tests of these theories by local probes are highly sought for. Our local measurements designed to concurrently probe spin and orbital/lattice degrees of freedom of Ba2NaOsO6 provide such tests. Here we show that a canted ferromagnetic phase which is preceded by local point symmetry breaking is stabilized at low temperatures, as predicted by quantum theories involving multipolar spin interactions.
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Affiliation(s)
- L Lu
- Department of Physics, Brown University, Providence, Rhode Island 02912, USA
| | - M Song
- Department of Physics, Brown University, Providence, Rhode Island 02912, USA
| | - W Liu
- Department of Physics, Brown University, Providence, Rhode Island 02912, USA
| | - A P Reyes
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA
| | - P Kuhns
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA
| | - H O Lee
- Department of Applied Physics and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA.,Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - I R Fisher
- Department of Applied Physics and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA.,Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - V F Mitrović
- Department of Physics, Brown University, Providence, Rhode Island 02912, USA
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Abstract
Neutron reflectometry has been combined with rheology in order to investigate the solid boundary of liquids and polymers under shear deformation. This approach allows one to apply a controlled stress to a material while resolving the structural arrangements on the sub-nanometre length scale with neutron reflectivity, off-specular scattering and small-angle scattering at the same time. The specularly reflected neutron intensity of a 20% by weight solution of Pluronic F127 in deuterated water in contact with an octadecyl trichlorosilane-covered and a piranha-treated silicon wafer is evaluated. A pronounced difference is found in the structure formed by the polymer micelles at the two surfaces, which is explained by the difference in the affinity of the micellar shell to the solid interfaces. Under deformation, the near interface structure changes at deformations of about 2, 30 and 900%. The structural changes are correlated with changes in the storage and loss modulus of the polymer solution, revealing a transition from more solid to more liquid like properties.
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Wright JA, Green E, Kuhns P, Reyes A, Brooks J, Schlueter J, Kato R, Yamamoto H, Kobayashi M, Brown SE. Zeeman-driven phase transition within the superconducting state of κ-(BEDT-TTF)2Cu(NCS)2. Phys Rev Lett 2011; 107:087002. [PMID: 21929196 DOI: 10.1103/physrevlett.107.087002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Indexed: 05/31/2023]
Abstract
(13)C nuclear magnetic resonance measurements were performed on κ-(BEDT-TTF)(2)Cu(NCS)(2), with the external field placed parallel to the quasi-2D conducting layers. The absorption spectrum is used to determine the electronic spin polarization M(s) as a function of external field H at a temperature T=0.35 K. A discontinuity in the derivative dM(s)/dH at an applied field of H(s)=213±3 kOe is taken as evidence for a Zeeman-driven transition within the superconducting state and stabilization of inhomogeneous superconductivity.
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Affiliation(s)
- J A Wright
- Department of Physics and Astronomy, UCLA, Los Angeles, California 90095-1547, USA
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Harter A, Lampropoulos C, Murugesu M, Kuhns P, Reyes A, Christou G, Dalal N. 55Mn nuclear spin relaxation in the truly axial single-molecule magnet Mn12-t-butylacetate thermally-activated down to 400mK. Polyhedron 2007. [DOI: 10.1016/j.poly.2006.11.039] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Zheng GQ, Ozaki H, Kitaoka Y, Kuhns P, Reyes AP, Moulton WG. Delocalized quasiparticles in the vortex state of an overdoped high-T(c) superconductor probed by 63Cu NMR. Phys Rev Lett 2002; 88:077003. [PMID: 11863931 DOI: 10.1103/physrevlett.88.077003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2001] [Indexed: 05/23/2023]
Abstract
We report the spin Knight shift (K(s)) and the nuclear spin-lattice relaxation rate (1/T1) in the vortex state as a function of magnetic field (H) up to 28 T in the high-Tc superconductor TlSr2CaCu2O6.8 (Tc = 68 K). At low temperatures well below Tc, both K(s) and 1/T1 measured around the middle point between the two nearest vortices (saddle point) increase substantially with increasing field, which indicate that the quasiparticle states with an ungapped spectrum are extended outside the vortex cores in a d-wave superconductor. The density of states (DOS) around the saddle point is found to be kappaN(0)square root[H/H(c2)], with kappa = 0.5-0.7 and N0 being the normal-state DOS.
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Affiliation(s)
- G-q Zheng
- Department of Physical Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
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Bryant PL, Harwell CR, Mrse AA, Emery EF, Gan Z, Caldwell T, Reyes AP, Kuhns P, Hoyt DW, Simeral LS, Hall RW, Butler LG. Structural characterization of MAO and related aluminum complexes. 1. Solid-state (27)Al NMR with comparison to EFG tensors from ab initio molecular orbital calculations. J Am Chem Soc 2001; 123:12009-17. [PMID: 11724609 DOI: 10.1021/ja011092a] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [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
Experimental and ab initio molecular orbital techniques are developed for study of aluminum species with large quadrupole coupling constants to test structural models for methylaluminoxanes (MAO). The techniques are applied to nitrogen- and oxygen-containing complexes of aluminum and to solid MAO isolated from active commercial MAO preparations. (Aminato)- and (propanolato)aluminum clusters with 3-, 4-, and 6-coordinate aluminum sites are studied with three (27)Al NMR techniques optimized for large (27)Al quadrupole coupling constants: field-swept, frequency-stepped, and high-field MAS NMR. Four-membered (aminato)aluminum complexes with AlN(4) coordination yield slightly smaller C(q) values than similar AlN(2)C(2) sites: 12.2 vs 15.8 MHz. Planar 3-coordinate AlN(2)C sites have the largest C(q) values, 37 MHz. In all cases, molecular orbital calculations of the electric field gradient tensors yields C(q) and eta values that match with experiment, even for a large hexameric (aminato)aluminum cage. A D(3d) symmetry hexaaluminum oxane cluster, postulated as a model for MAO, yields a calculated C(q) of -23.7 MHz, eta = 0.7474, and predicts a spectrum that is too broad to match the field-swept NMR of methylaluminoxane, which shows at least three sites, all with C(q) values greater than 15 MHz but less than 21 MHz. Thus, the proposed hexaaluminum cluster, with its strained four-membered rings, is not a major component of MAO. However, calculations for dimers of the cage complex, either edge-bridged or face-bridged, show a much closer match to experiment. Also, MAO preparations differ, with a gel form of MAO having significantly larger (27)Al C(q) values than a nongel form, a conclusion reached on the basis of (27)Al NMR line widths in field-swept NMR spectra acquired from 13 to 24 T.
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Affiliation(s)
- P L Bryant
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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Mitrović VF, Sigmund EE, Eschrig M, Bachman HN, Halperin WP, Reyes AP, Kuhns P, Moulton WG. Spatially resolved electronic structure inside and outside the vortex cores of a high-temperature superconductor. Nature 2001; 413:501-4. [PMID: 11586354 DOI: 10.1038/35097039] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Puzzling aspects of high-transition-temperature (high-Tc) superconductors include the prevalence of magnetism in the normal state and the persistence of superconductivity in high magnetic fields. Superconductivity and magnetism generally are thought to be incompatible, based on what is known about conventional superconductors. Recent results, however, indicate that antiferromagnetism can appear in the superconducting state of a high-Tc superconductor in the presence of an applied magnetic field. Magnetic fields penetrate a superconductor in the form of quantized flux lines, each of which represents a vortex of supercurrents. Superconductivity is suppressed in the core of the vortex and it has been suggested that antiferromagnetism might develop there. Here we report the results of a high-field nuclear-magnetic-resonance (NMR) imaging experiment in which we spatially resolve the electronic structure of near-optimally doped YBa2Cu3O7-delta inside and outside vortex cores. Outside the cores, we find strong antiferromagnetic fluctuations, whereas inside we detect electronic states that are rather different from those found in conventional superconductors.
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Affiliation(s)
- V F Mitrović
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
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Zheng G, Ozaki H, Clark WG, Kitaoka Y, Kuhns P, Reyes AP, Moulton WG, Kondo T, Shimakawa Y, Kubo Y. Superconducting fluctuations and the pseudogap in the slightly overdoped high- T(c) superconductor TlSr2CaCu2O6.8: high magnetic field NMR studies. Phys Rev Lett 2000; 85:405-408. [PMID: 10991294 DOI: 10.1103/physrevlett.85.405] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2000] [Indexed: 05/23/2023]
Abstract
From measurements of the 63Cu Knight shift ( K) and the nuclear spin-lattice relaxation rate ( 1/T1) under magnetic fields from zero up to 28 T in the slightly overdoped high- T(c) superconductor TlSr2CaCu2O6.8 ( T(c) = 68 K), we find that the pseudogap behavior, i.e., the reductions of 1/T1T and K above T(c) from the values expected from the normal state at high T, is strongly field dependent and follows a scaling relation. We show that this scaling is consistent with the effects of the Cooper pair density fluctuations. The present finding contrasts sharply with the pseudogap property reported previously in the underdoped regime where no field effect was seen up to 23.2 T. The implications are discussed.
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Affiliation(s)
- Gq Zheng
- Department of Physical Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
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Bryant PL, Butler LG, Reyes AP, Kuhns P. 27Al field-swept and frequency-stepped NMR for sites with large quadrupole coupling constants. Solid State Nucl Magn Reson 2000; 16:63-67. [PMID: 10811430 DOI: 10.1016/s0926-2040(00)00055-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Spectra of nonspinning samples with large quadrupole coupling constants, 16-32 MHz, are acquired by frequency-stepping. A series of spin-echoes are acquired at arbitrary frequency increments, frequency-shifted in the time domain, and co-added as magnitude spectra. This procedure is derived from a method in use for field-swept NMR. The two methods are compared.
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Affiliation(s)
- P L Bryant
- Department of Chemistry, Louisiana State University, Baton Rouge 70803-1804, USA
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