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Quintanilla J, Jia Y, Pruess BS, Chavez J, Gall CM, Lynch G, Gunn BG. Pre- versus Post-synaptic Forms of LTP in Two Branches of the Same Hippocampal Afferent. J Neurosci 2024; 44:e1449232024. [PMID: 38326038 PMCID: PMC10919254 DOI: 10.1523/jneurosci.1449-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 12/18/2023] [Accepted: 01/22/2024] [Indexed: 02/09/2024] Open
Abstract
There has been considerable controversy about pre- versus postsynaptic expression of memory-related long-term potentiation (LTP), with corresponding disputes about underlying mechanisms. We report here an instance in male mice, in which both types of potentiation are expressed but in separate branches of the same hippocampal afferent. Induction of LTP in the dentate gyrus (DG) branch of the lateral perforant path (LPP) reduces paired-pulse facilitation, is blocked by antagonism of cannabinoid receptor type 1, and is not affected by suppression of postsynaptic actin polymerization. These observations are consistent with presynaptic expression. The opposite pattern of results was obtained in the LPP branch that innervates the distal dendrites of CA3: LTP did not reduce paired-pulse facilitation, was unaffected by the cannabinoid receptor blocker, and required postsynaptic actin filament assembly. Differences in the two LPP termination sites were also noted for frequency facilitation of synaptic responses, an effect that was reproduced in a two-step simulation by small adjustments to vesicle release dynamics. These results indicate that different types of glutamatergic neurons impose different forms of filtering and synaptic plasticity on their afferents. They also suggest that inputs are routed to, and encoded by, different sites within the hippocampus depending upon the pattern of activity arriving over the parent axon.
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Affiliation(s)
- J Quintanilla
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
| | - Y Jia
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
| | - B S Pruess
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
| | - J Chavez
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
| | - C M Gall
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
- Neurobiology & Behavior, University of California, Irvine, California 92697
| | - G Lynch
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
- Psychiatry & Human Behavior, University of California, Irvine, California 92697
| | - B G Gunn
- Department of Anatomy & Neurobiology, University of California, Irvine, California 92697
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Tula T, Möller G, Quintanilla J, Giblin SR, Hillier AD, McCabe EE, Ramos S, Barker DS, Gibson S. Machine learning approach to muon spectroscopy analysis. J Phys Condens Matter 2021; 33:194002. [PMID: 33545697 DOI: 10.1088/1361-648x/abe39e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
In recent years, artificial intelligence techniques have proved to be very successful when applied to problems in physical sciences. Here we apply an unsupervised machine learning (ML) algorithm called principal component analysis (PCA) as a tool to analyse the data from muon spectroscopy experiments. Specifically, we apply the ML technique to detect phase transitions in various materials. The measured quantity in muon spectroscopy is an asymmetry function, which may hold information about the distribution of the intrinsic magnetic field in combination with the dynamics of the sample. Sharp changes of shape of asymmetry functions-measured at different temperatures-might indicate a phase transition. Existing methods of processing the muon spectroscopy data are based on regression analysis, but choosing the right fitting function requires knowledge about the underlying physics of the probed material. Conversely, PCA focuses on small differences in the asymmetry curves and works without any prior assumptions about the studied samples. We discovered that the PCA method works well in detecting phase transitions in muon spectroscopy experiments and can serve as an alternative to current analysis, especially if the physics of the studied material are not entirely known. Additionally, we found out that our ML technique seems to work best with large numbers of measurements, regardless of whether the algorithm takes data only for a single material or whether the analysis is performed simultaneously for many materials with different physical properties.
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Affiliation(s)
- T Tula
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
| | - G Möller
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
| | - J Quintanilla
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
| | - S R Giblin
- School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom
| | - A D Hillier
- ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot Oxon, OX11 0QX, United Kingdom
| | - E E McCabe
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
| | - S Ramos
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
| | - D S Barker
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - S Gibson
- School of Physical Sciences, University of Kent, Park Wood Rd, Canterbury CT2 7NH, United Kingdom
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Shang T, Smidman M, Ghosh SK, Baines C, Chang LJ, Gawryluk DJ, Barker JAT, Singh RP, Paul DM, Balakrishnan G, Pomjakushina E, Shi M, Medarde M, Hillier AD, Yuan HQ, Quintanilla J, Mesot J, Shiroka T. Time-Reversal Symmetry Breaking in Re-Based Superconductors. Phys Rev Lett 2018; 121:257002. [PMID: 30608781 DOI: 10.1103/physrevlett.121.257002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 07/30/2018] [Indexed: 06/09/2023]
Abstract
To trace the origin of time-reversal symmetry breaking (TRSB) in Re-based superconductors, we performed comparative muon-spin rotation and relaxation (μSR) studies of superconducting noncentrosymmetric Re_{0.82}Nb_{0.18} (T_{c}=8.8 K) and centrosymmetric Re (T_{c}=2.7 K). In Re_{0.82}Nb_{0.18}, the low-temperature superfluid density and the electronic specific heat evidence a fully gapped superconducting state, whose enhanced gap magnitude and specific-heat discontinuity suggest a moderately strong electron-phonon coupling. In both Re_{0.82}Nb_{0.18} and pure Re, the spontaneous magnetic fields revealed by zero-field μSR below T_{c} indicate time-reversal symmetry breaking and thus unconventional superconductivity. The concomitant occurrence of TRSB in centrosymmetric Re and noncentrosymmetric ReT (T=transition metal), yet its preservation in the isostructural noncentrosymmetric superconductors Mg_{10}Ir_{19}B_{16} and Nb_{0.5}Os_{0.5}, strongly suggests that the local electronic structure of Re is crucial for understanding the TRSB superconducting state in Re and ReT. We discuss the superconducting order parameter symmetries that are compatible with the experimental observations.
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Affiliation(s)
- T Shang
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Villigen CH-5232, Switzerland
- Swiss Light Source, Paul Scherrer Institut, Villigen CH-5232, Switzerland
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH-1015, Switzerland
| | - M Smidman
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - S K Ghosh
- School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - C Baines
- Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - L J Chang
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
| | - D J Gawryluk
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Villigen CH-5232, Switzerland
| | - J A T Barker
- Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - R P Singh
- Indian Institute of Science Education and Research Bhopal, Bhopal, 462066, India
| | - D McK Paul
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - G Balakrishnan
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - E Pomjakushina
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Villigen CH-5232, Switzerland
| | - M Shi
- Swiss Light Source, Paul Scherrer Institut, Villigen CH-5232, Switzerland
| | - M Medarde
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, Villigen CH-5232, Switzerland
| | - A D Hillier
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire, OX11 0QX, United Kingdom
| | - H Q Yuan
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing Univeristy, Nanjing 210093, China
| | - J Quintanilla
- School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - J Mesot
- Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH-1015, Switzerland
- Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zurich, Switzerland
| | - T Shiroka
- Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zurich, Switzerland
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Weng ZF, Zhang JL, Smidman M, Shang T, Quintanilla J, Annett JF, Nicklas M, Pang GM, Jiao L, Jiang WB, Chen Y, Steglich F, Yuan HQ. Two-Gap Superconductivity in LaNiGa_{2} with Nonunitary Triplet Pairing and Even Parity Gap Symmetry. Phys Rev Lett 2016; 117:027001. [PMID: 27447519 DOI: 10.1103/physrevlett.117.027001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Indexed: 06/06/2023]
Abstract
The nature of the pairing states of superconducting LaNiC_{2} and LaNiGa_{2} has to date remained a puzzling question. Broken time reversal symmetry has been observed in both compounds and a group theoretical analysis implies a nonunitary triplet pairing state. However, all the allowed nonunitary triplet states have nodal gap functions but most thermodynamic and NMR measurements indicate fully gapped superconductivity in LaNiC_{2}. Here we probe the gap symmetry of LaNiGa_{2} by measuring the London penetration depth, specific heat, and upper critical field. These measurements demonstrate two-gap nodeless superconductivity in LaNiGa_{2}, suggesting that this is a common feature of both compounds. These results allow us to propose a novel triplet superconducting state, where the pairing occurs between electrons of the same spin, but on different orbitals. In this case the superconducting wave function has a triplet spin component but isotropic even parity gap symmetry, yet the overall wave function remains antisymmetric under particle exchange. This model leads to a nodeless two-gap superconducting state which breaks time reversal symmetry, and therefore accounts well for the seemingly contradictory experimental results.
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Affiliation(s)
- Z F Weng
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - J L Zhang
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - M Smidman
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - T Shang
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - J Quintanilla
- SEPnet and Hubbard Theory Consortium, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - J F Annett
- H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - M Nicklas
- Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
| | - G M Pang
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - L Jiao
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - W B Jiang
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - Y Chen
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
| | - F Steglich
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
- Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
| | - H Q Yuan
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
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Abstract
We study properties of the clusters of a system of fully penetrable balls, a model formed by centering equal-sized balls on the points of a Poisson process. We develop a formal expression for the density of connected clusters ofkballs (calledk-mers) in the system, first rigorously derived by Penrose [15]. Our integral expressions are free of inherent redundancies, making them more tractable for numerical evaluation. We also derive and evaluate an integral expression for the average volume ofk-mers.
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Alanoca L, Amouroux D, Monperrus M, Tessier E, Goni M, Guyoneaud R, Acha D, Gassie C, Audry S, Garcia ME, Quintanilla J, Point D. Diurnal variability and biogeochemical reactivity of mercury species in an extreme high-altitude lake ecosystem of the Bolivian Altiplano. Environ Sci Pollut Res Int 2016; 23:6919-6933. [PMID: 26676541 DOI: 10.1007/s11356-015-5917-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 12/02/2015] [Indexed: 06/05/2023]
Abstract
Methylation and demethylation represent major transformation pathways regulating the net production of methylmercury (MMHg). Very few studies have documented Hg reactivity and transformation in extreme high-altitude lake ecosystems. Mercury (Hg) species concentrations (IHg, MMHg, Hg°, and DMHg) and in situ Hg methylation (M) and MMHg demethylation (D) potentials were determined in water, sediment, floating organic aggregates, and periphyton compartments of a shallow productive Lake of the Bolivian Altiplano (Uru Uru Lake, 3686 m). Samples were collected during late dry season (October 2010) and late wet season (May 2011) at a north (NS) and a south (SS) site of the lake, respectively. Mercury species concentrations exhibited significant diurnal variability as influenced by the strong diurnal biogeochemical gradients. Particularly high methylated mercury concentrations (0.2 to 4.5 ng L(-1) for MMHgT) were determined in the water column evidencing important Hg methylation in this ecosystem. Methylation and D potentials range were, respectively, <0.1-16.5 and <0.2-68.3 % day(-1) and were highly variable among compartments of the lake, but always higher during the dry season. Net Hg M indicates that the influence of urban and mining effluent (NS) promotes MMHg production in both water (up to 0.45 ng MMHg L(-1) day(-1)) and sediment compartments (2.0 to 19.7 ng MMHg g(-1) day(-1)). While the sediment compartment appears to represent a major source of MMHg in this shallow ecosystem, floating organic aggregates (dry season, SS) and Totora's periphyton (wet season, NS) were found to act as a significant source (5.8 ng MMHg g(-1) day(-1)) and a sink (-2.1 ng MMHg g(-1) day(-1)) of MMHg, respectively. This work demonstrates that high-altitude productive lake ecosystems can promote MMHg formation in various compartments supporting recent observations of high Hg contents in fish and water birds.
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Affiliation(s)
- L Alanoca
- Géosciences Environnement Toulouse, UMR 5563-IRD UR 234, Université Paul Sabatier, 14 Avenue Edouard Belin, 31400, Toulouse, France
| | - D Amouroux
- Géosciences Environnement Toulouse, UMR 5563-IRD UR 234, Université Paul Sabatier, 14 Avenue Edouard Belin, 31400, Toulouse, France.
- Laboratoire de Chimie Analytique Bio-inorganique et Environnement, IPREM UMR 5254 CNRS, Université de Pau et des Pays de l'Adour, Hélioparc Pau Pyrénées, 2, av. P. Angot, 64053, Pau cedex 9, France.
| | - M Monperrus
- Laboratoire de Chimie Analytique Bio-inorganique et Environnement, IPREM UMR 5254 CNRS, Université de Pau et des Pays de l'Adour, Hélioparc Pau Pyrénées, 2, av. P. Angot, 64053, Pau cedex 9, France
| | - E Tessier
- Laboratoire de Chimie Analytique Bio-inorganique et Environnement, IPREM UMR 5254 CNRS, Université de Pau et des Pays de l'Adour, Hélioparc Pau Pyrénées, 2, av. P. Angot, 64053, Pau cedex 9, France
| | - M Goni
- Equipe Environnement et Microbiologie, IPREM UMR 5254 CNRS, Université de Pau et des Pays de l'Adour, Bâtiment IBEAS, BP1153, 64013, Pau Cedex, France
| | - R Guyoneaud
- Equipe Environnement et Microbiologie, IPREM UMR 5254 CNRS, Université de Pau et des Pays de l'Adour, Bâtiment IBEAS, BP1153, 64013, Pau Cedex, France
| | - D Acha
- Laboratorio de Calidad Ambiental, Instituto de Ecologia, Universidad Mayor de San Andres, Campus Universitario de Cota Cota, casilla 3161, La Paz, Bolivia
| | - C Gassie
- Equipe Environnement et Microbiologie, IPREM UMR 5254 CNRS, Université de Pau et des Pays de l'Adour, Bâtiment IBEAS, BP1153, 64013, Pau Cedex, France
| | - S Audry
- Géosciences Environnement Toulouse, UMR 5563-IRD UR 234, Université Paul Sabatier, 14 Avenue Edouard Belin, 31400, Toulouse, France
| | - M E Garcia
- Laboratorio de Hidroquímica, Instituto de Investigaciones Químicas, Universidad Mayor de San Andres, Campus Universitario de Cota Cota, casilla 3161, La Paz, Bolivia
| | - J Quintanilla
- Laboratorio de Hidroquímica, Instituto de Investigaciones Químicas, Universidad Mayor de San Andres, Campus Universitario de Cota Cota, casilla 3161, La Paz, Bolivia
| | - D Point
- Géosciences Environnement Toulouse, UMR 5563-IRD UR 234, Université Paul Sabatier, 14 Avenue Edouard Belin, 31400, Toulouse, France
- Laboratorio de Calidad Ambiental, Instituto de Ecologia, Universidad Mayor de San Andres, Campus Universitario de Cota Cota, casilla 3161, La Paz, Bolivia
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Espirito Santo J, Seabra M, Mateus C, Morais P, Leitao J, Quintanilla J. OSTEOMED – Surgical Instrument with variable angle for Dentists. Med Oral Patol Oral Cir Bucal 2015. [DOI: 10.4317/medoral.17643905] [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: 11/05/2022] Open
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Singh RP, Hillier AD, Mazidian B, Quintanilla J, Annett JF, Paul DM, Balakrishnan G, Lees MR. Detection of time-reversal symmetry breaking in the noncentrosymmetric superconductor Re6Zr using muon-spin spectroscopy. Phys Rev Lett 2014; 112:107002. [PMID: 24679322 DOI: 10.1103/physrevlett.112.107002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Indexed: 06/03/2023]
Abstract
We have investigated the superconducting state of the noncentrosymmetric compound Re6Zr using magnetization, heat capacity, and muon-spin relaxation or rotation (μSR) measurements. Re6Zr has a superconducting transition temperature, Tc=6.75±0.05 K. Transverse-field μSR experiments, used to probe the superfluid density, suggest an s-wave character for the superconducting gap. However, zero and longitudinal-field μSR data reveal the presence of spontaneous static magnetic fields below Tc indicating that time-reversal symmetry is broken in the superconducting state and an unconventional pairing mechanism. An analysis of the pairing symmetries identifies the ground states compatible with time-reversal symmetry breaking.
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Affiliation(s)
- R P Singh
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - A D Hillier
- ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire OX11 0QX, United Kingdom
| | - B Mazidian
- ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire OX11 0QX, United Kingdom and H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - J Quintanilla
- ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire OX11 0QX, United Kingdom and SEPnet and Hubbard Theory Consortium, School of Physical Sciences, University of Kent, Canterbury CT2 7NH, United Kingdom
| | - J F Annett
- H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - D McK Paul
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - G Balakrishnan
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - M R Lees
- Physics Department, University of Warwick, Coventry CV4 7AL, United Kingdom
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Hillier AD, Quintanilla J, Mazidian B, Annett JF, Cywinski R. Nonunitary triplet pairing in the centrosymmetric superconductor LaNiGa2. Phys Rev Lett 2012; 109:097001. [PMID: 23002872 DOI: 10.1103/physrevlett.109.097001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Indexed: 06/01/2023]
Abstract
Muon spin rotation and relaxation experiments on the centrosymmetric intermetallic superconductor LaNiGa2 are reported. The appearance of spontaneous magnetic fields coincides with the onset of superconductivity, implying that the superconducting state breaks time reversal symmetry, similarly to noncentrosymmetric LaNiC2. Only four triplet states are compatible with this observation, all of which are nonunitary triplets. This suggests that LaNiGa2 is the centrosymmetric analogue of LaNiC2. We argue that these materials are representatives of a new family of paramagnetic nonunitary superconductors.
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Affiliation(s)
- A D Hillier
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire, United Kingdom
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Hillier AD, Quintanilla J, Cywinski R. Evidence for time-reversal symmetry breaking in the noncentrosymmetric superconductor LaNiC2. Phys Rev Lett 2009; 102:117007. [PMID: 19392234 DOI: 10.1103/physrevlett.102.117007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Indexed: 05/27/2023]
Abstract
Muon spin relaxation experiments on the noncentrosymmetric intermetallic superconductor LaNiC2 are reported. We find that the onset of superconductivity coincides with the appearance of spontaneous magnetic fields, implying that in the superconducting state time-reversal symmetry is broken. An analysis of the possible pairing symmetries suggests only four triplet states compatible with this observation, all of them nonunitary. They include the intriguing possibility of triplet pairing with the full point group symmetry of the crystal, which is possible only in a noncentrosymmetric superconductor.
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Affiliation(s)
- A D Hillier
- ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire, OX11 0QX, United Kingdom
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Campo VL, Capelle K, Quintanilla J, Hooley C. Quantitative determination of the hubbard model phase diagram from optical lattice experiments by two-parameter scaling. Phys Rev Lett 2007; 99:240403. [PMID: 18233426 DOI: 10.1103/physrevlett.99.240403] [Citation(s) in RCA: 1] [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: 06/06/2007] [Indexed: 05/25/2023]
Abstract
We propose an experiment to obtain the phase diagram of the fermionic Hubbard model, for any dimensionality, using cold atoms in optical lattices. It is based on measuring the total energy for a sequence of trap profiles. It combines finite-size scaling with an additional "finite-curvature scaling" necessary to reach the homogeneous limit. We illustrate its viability in the 1D case, simulating experimental data in the Bethe-ansatz local-density approximation. Including experimental errors, the filling corresponding to the Mott transition can be determined with better than 3% accuracy.
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Affiliation(s)
- V L Campo
- Centro Internacional de Física de Matéria Condensada, Universidade de Brasília, Caixa Postal 04513, 70919-970 Brasília, Brazil
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Quintanilla J, Capelle K, Oliveira LN. Comment on "Anomalous proximity effect in underdoped YBa2Cu3O6+x Josephson junctions". Phys Rev Lett 2003; 90:089703. [PMID: 12633473 DOI: 10.1103/physrevlett.90.089703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2002] [Indexed: 05/24/2023]
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Quintanilla J. Measurement of the percolation threshold for fully penetrable disks of different radii. Phys Rev E Stat Nonlin Soft Matter Phys 2001; 63:061108. [PMID: 11415069 DOI: 10.1103/physreve.63.061108] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2000] [Indexed: 11/07/2022]
Abstract
We perform simulations of gradient percolation to study the percolation threshold for systems of homogeneous fully penetrable disks of variable radii. We find that, if the radii follow a uniform distribution, the percolation threshold is 0.686 610+/-0.000 007. We also investigate binary dispersions, studying the influence of constitutive parameters on the percolation threshold and suggesting an empirical formula for the threshold. We find that, with the appropriate parameters, a percolation threshold of approximately 0.76 can be achieved. The minimal threshold of 0.676 339+/-0.000 004 is achieved by disks of equal radius.
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Affiliation(s)
- J Quintanilla
- Department of Mathematics, University of North Texas, Denton, Texas 76203, USA.
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Quintanilla J. Microstructure functions for random media with impenetrable particles. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999; 60:5788-94. [PMID: 11970476 DOI: 10.1103/physreve.60.5788] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/1999] [Indexed: 04/18/2023]
Abstract
We introduce a model consisting of nonaligned and impenetrable particles. This model is obtained by placing particles of random orientation within "security spheres," typically chosen to be spheres in thermal equilibrium. The particles in general are allowed to be nonspherical. We obtain an analytical expression for the function S(n), the probability that n points simultaneously lie outside of the particle phase. This characterization of the microstructure appears in certain rigorous bounds on the effective properties of random materials. We also evaluate S2 for various specific examples of this model, including nonaligned impenetrable ellipsoids.
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Affiliation(s)
- J Quintanilla
- Department of Mathematics, University of North Texas, Denton, Texas 76203, USA.
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Quintanilla J, Torquato S. Clustering properties of d-dimensional overlapping spheres. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1996; 54:5331-5339. [PMID: 9965718 DOI: 10.1103/physreve.54.5331] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Quintanilla J, Torquato S. Lineal measures of clustering in overlapping particle systems. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1996; 54:4027-4036. [PMID: 9965551 DOI: 10.1103/physreve.54.4027] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Quintanilla J, Torquato S. Microstructure and conductivity of hierarchical laminate composites. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1996; 53:4368-4378. [PMID: 9964770 DOI: 10.1103/physreve.53.4368] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Quintanilla J. A half-day treatment program. Hosp Community Psychiatry 1966; 17:161. [PMID: 5931319 DOI: 10.1176/ps.17.6.161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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