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Fittipaldi R, Hartmann R, Mercaldo MT, Komori S, Bjørlig A, Kyung W, Yasui Y, Miyoshi T, Olde Olthof LAB, Palomares Garcia CM, Granata V, Keren I, Higemoto W, Suter A, Prokscha T, Romano A, Noce C, Kim C, Maeno Y, Scheer E, Kalisky B, Robinson JWA, Cuoco M, Salman Z, Vecchione A, Di Bernardo A. Unveiling unconventional magnetism at the surface of Sr 2RuO 4. Nat Commun 2021; 12:5792. [PMID: 34608149 PMCID: PMC8490454 DOI: 10.1038/s41467-021-26020-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [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: 03/30/2021] [Accepted: 09/14/2021] [Indexed: 11/09/2022] Open
Abstract
Materials with strongly correlated electrons often exhibit interesting physical properties. An example of these materials is the layered oxide perovskite Sr2RuO4, which has been intensively investigated due to its unusual properties. Whilst the debate on the symmetry of the superconducting state in Sr2RuO4 is still ongoing, a deeper understanding of the Sr2RuO4 normal state appears crucial as this is the background in which electron pairing occurs. Here, by using low-energy muon spin spectroscopy we discover the existence of surface magnetism in Sr2RuO4 in its normal state. We detect static weak dipolar fields yet manifesting at an onset temperature higher than 50 K. We ascribe this unconventional magnetism to orbital loop currents forming at the reconstructed Sr2RuO4 surface. Our observations set a reference for the discovery of the same magnetic phase in other materials and unveil an electronic ordering mechanism that can influence electron pairing with broken time reversal symmetry.
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Affiliation(s)
- R Fittipaldi
- CNR-SPIN, c/o University of Salerno, I-84084, Fisciano, Salerno, Italy.,Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - R Hartmann
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - M T Mercaldo
- Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - S Komori
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK.,Department of Physics, Nagoya University, Nagoya, 464-8602, Japan
| | - A Bjørlig
- Department of Physics, Bar Ilan University, Ramat Gan, 5920002, Israel
| | - W Kyung
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea
| | - Y Yasui
- Department of Physics, Kyoto University, Kyoto, 606-8502, Japan.,RIKEN, Centre for Emergent Matter Science, Saitama, 351-0198, Japan
| | - T Miyoshi
- Department of Physics, Kyoto University, Kyoto, 606-8502, Japan
| | - L A B Olde Olthof
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK
| | - C M Palomares Garcia
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK
| | - V Granata
- Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - I Keren
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232, Villigen, PSI, Switzerland.,The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - W Higemoto
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan
| | - A Suter
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232, Villigen, PSI, Switzerland
| | - T Prokscha
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232, Villigen, PSI, Switzerland
| | - A Romano
- CNR-SPIN, c/o University of Salerno, I-84084, Fisciano, Salerno, Italy.,Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - C Noce
- CNR-SPIN, c/o University of Salerno, I-84084, Fisciano, Salerno, Italy.,Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - C Kim
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea
| | - Y Maeno
- Department of Physics, Kyoto University, Kyoto, 606-8502, Japan
| | - E Scheer
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - B Kalisky
- Department of Physics, Bar Ilan University, Ramat Gan, 5920002, Israel
| | - J W A Robinson
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK
| | - M Cuoco
- CNR-SPIN, c/o University of Salerno, I-84084, Fisciano, Salerno, Italy. .,Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy.
| | - Z Salman
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232, Villigen, PSI, Switzerland.
| | - A Vecchione
- CNR-SPIN, c/o University of Salerno, I-84084, Fisciano, Salerno, Italy.,Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - A Di Bernardo
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany.
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Duca KA, Lam V, Keren I, Endler EE, Letchworth GJ, Novella IS, Yin J. Quantifying viral propagation in vitro: toward a method for characterization of complex phenotypes. Biotechnol Prog 2001; 17:1156-65. [PMID: 11735454 DOI: 10.1021/bp010115m] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
For a eukaryotic virus to successfully infect and propagate in cultured cells several events must occur: the virion must identify and bind to its cellular receptor, become internalized, uncoat, synthesize viral proteins, replicate its genome, assemble progeny virions, and exit the host cell. While these events are taking place, intrinsic host defenses activate in order to defeat the virus, e.g., activation of the interferon system, induction of apoptosis, and attempted elicitation of immune responses via chemokine and cytokine production. As a first step in developing an imaging methodology to facilitate direct observation of such complex host/virus dynamics, we have designed an immunofluorescence-based system that extends the traditional plaque assay, permitting simultaneous quantification of the rate of viral spread, as indicated by the presence of a labeled viral protein, and cell death in vitro, as indicated by cell loss. We propose that our propagation and cell death profiles serve as phenotypic read-outs, complementing genetic analysis of viral strains. As our virus/host system we used vesicular stomatitis virus (VSV) propagating in hamster kidney epithelial (BHK-21) and murine astrocytoma (DBT) cell lines. Viral propagation and death profiles were strikingly different in these two cell lines, displaying both very different initial titer and cell age effects. The rate of viral spread and cell death tracked reliably in both cell lines. In BHK-21 cells, the rate of viral propagation, as well as maximal spread, was relatively insensitive to initial titer and was roughly linear over several days. In contrast, viral plaque expansion in DBT cells was contained early in the infections with high titers, while low titer infections spread in a manner similar to the BHK-21 cells. The effect of cell age on infection spread was negligible in BHK-21 cells but not in DBTs. Neither of these effects was clearly observed by plaque assay.
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Affiliation(s)
- K A Duca
- Department of Chemical Engineering, University of Wisconsin, Madison, Wisconsin, USA
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