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Topological Doping and Superconductivity in Cuprates: An Experimental Perspective. Symmetry (Basel) 2021. [DOI: 10.3390/sym13122365] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Hole doping into a correlated antiferromagnet leads to topological stripe correlations, involving charge stripes that separate antiferromagnetic spin stripes of opposite phases. The topological spin stripe order causes the spin degrees of freedom within the charge stripes to feel a geometric frustration with their environment. In the case of cuprates, where the charge stripes have the character of a hole-doped two-leg spin ladder, with corresponding pairing correlations, anti-phase Josephson coupling across the spin stripes can lead to a pair-density-wave order in which the broken translation symmetry of the superconducting wave function is accommodated by pairs with finite momentum. This scenario is now experimentally verified by recently reported measurements on La2−xBaxCuO4 with x=1/8. While pair-density-wave order is not common as a cuprate ground state, it provides a basis for understanding the uniform d-wave order that is more typical in superconducting cuprates.
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Kofu M, Watanuki R, Sakakibara T, Ohira-Kawamura S, Nakajima K, Matsuura M, Ueki T, Akutsu K, Yamamuro O. Spin glass behavior and magnetic boson peak in a structural glass of a magnetic ionic liquid. Sci Rep 2021; 11:12098. [PMID: 34103650 PMCID: PMC8187720 DOI: 10.1038/s41598-021-91619-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 05/28/2021] [Indexed: 11/30/2022] Open
Abstract
Glassy magnetic behavior has been observed in a wide range of crystalline magnetic materials called spin glass. Here, we report spin glass behavior in a structural glass of a magnetic ionic liquid, C4mimFeCl4. Magnetization measurements demonstrate that an antiferromagnetic ordering occurs at TN = 2.3 K in the crystalline state, while a spin glass transition occurs at TSG = 0.4 K in the structural glass state. In addition, localized magnetic excitations were found in the spin glass state by inelastic neutron scattering, in contrast to spin-wave excitations in the ordered phase of the crystalline sample. The localized excitation was scaled by the Bose population factor below TSG and gradually disappeared above TSG. This feature is highly reminiscent of boson peaks commonly observed in structural glasses. We suggest the "magnetic" boson peak to be one of the inherent dynamics of a spin glass state.
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Affiliation(s)
- Maiko Kofu
- J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan.
| | - Ryuta Watanuki
- Division of Materials Science and Chemical Engineering, Faculty of Engineering, Yokohama National University, Yokohama, Kanagawa, 240-8501, Japan.
| | - Toshiro Sakakibara
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | | | - Kenji Nakajima
- J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan
| | - Masato Matsuura
- Comprehensive Research Organization for Science and Society, Tokai, Ibaraki, 319-1106, Japan
| | - Takeshi Ueki
- National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044, Japan
- Graduate School of Life Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan
| | - Kazuhiro Akutsu
- Comprehensive Research Organization for Science and Society, Tokai, Ibaraki, 319-1106, Japan
| | - Osamu Yamamuro
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
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Commensurate antiferromagnetic excitations as a signature of the pseudogap in the tetragonal high-Tc cuprate HgBa2CuO(4+δ). Nat Commun 2016; 7:10819. [PMID: 26940332 PMCID: PMC4785222 DOI: 10.1038/ncomms10819] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 01/22/2016] [Indexed: 11/23/2022] Open
Abstract
Antiferromagnetic correlations have been argued to be the cause of the d-wave superconductivity and the pseudogap phenomena exhibited by the cuprates. Although the antiferromagnetic response in the pseudogap state has been reported for a number of compounds, there exists no information for structurally simple HgBa2CuO4+δ. Here we report neutron-scattering results for HgBa2CuO4+δ (superconducting transition temperature Tc≈71 K, pseudogap temperature T*≈305 K) that demonstrate the absence of the two most prominent features of the magnetic excitation spectrum of the cuprates: the X-shaped ‘hourglass' response and the resonance mode in the superconducting state. Instead, the response is Y-shaped, gapped and significantly enhanced below T*, and hence a prominent signature of the pseudogap state. In the cuprates, antiferromagnetic correlations might be the cause of the pseudogap phenomenon. Here the authors use neutron scattering on the tetragonal cuprate HgBa2CuO4+δ revealing commensurate antiferromagnetic excitations as a signature of the pseudogap state.
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Mydosh JA. Spin glasses: redux: an updated experimental/materials survey. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2015; 78:052501. [PMID: 25872613 DOI: 10.1088/0034-4885/78/5/052501] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This article reviews the 40+ year old spin-glass field and one of its earliest model interpretations as a spin density wave. Our description is from an experimental phenomenological point of view with emphasis on new spin glass materials and their relation to topical problems and strongly correlated materials in condensed matter physics. We first simply define a spin glass (SG), give its basic ingredients and explain how the spin glasses enter into the statistical mechanics of classical phase transitions. We then consider the four basic experimental properties to solidly characterize canonical spin glass behavior and introduce the early theories and models. Here the spin density wave (SDW) concept is used to explain the difference between a short-range SDW, i.e. a SG and, in contrast, a long-range SDW, i.e. a conventional magnetic phase transition. We continue with the present state of SG, its massive computer simulations and recent proposals of chiral glasses and quantum SG. We then collect and mention the various SG 'spin-off's'. A major section uncovers the fashionable unconventional materials that display SG-like freezing and glassy ground states, such as (high temperature) superconductors, heavy fermions, intermetallics and Heuslers, pyrochlor and spinels, oxides and chalogenides and exotics, e.g. quasicrystals. Some conclusions and future directions complete the review.
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Affiliation(s)
- J A Mydosh
- Kamerlingh Onnes Laboratory and Institute Lorentz, Leiden University, PO Box 9504, 2300RA Leiden, The Netherlands
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Peng Y, Meng J, Mou D, He J, Zhao L, Wu Y, Liu G, Dong X, He S, Zhang J, Wang X, Peng Q, Wang Z, Zhang S, Yang F, Chen C, Xu Z, Lee TK, Zhou XJ. Disappearance of nodal gap across the insulator-superconductor transition in a copper-oxide superconductor. Nat Commun 2014; 4:2459. [PMID: 24051514 DOI: 10.1038/ncomms3459] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 08/18/2013] [Indexed: 11/09/2022] Open
Abstract
The parent compound of the copper-oxide high-temperature superconductors is a Mott insulator. Superconductivity is realized by doping an appropriate amount of charge carriers. How a Mott insulator transforms into a superconductor is crucial in understanding the unusual physical properties of high-temperature superconductors and the superconductivity mechanism. Here we report high-resolution angle-resolved photoemission measurement on heavily underdoped Bi₂Sr₂-xLaxCuO(₆+δ) system. The electronic structure of the lightly doped samples exhibit a number of characteristics: existence of an energy gap along the nodal direction, d-wave-like anisotropic energy gap along the underlying Fermi surface, and coexistence of a coherence peak and a broad hump in the photoemission spectra. Our results reveal a clear insulator-superconductor transition at a critical doping level of ~0.10 where the nodal energy gap approaches zero, the three-dimensional antiferromagnetic order disappears, and superconductivity starts to emerge. These observations clearly signal a close connection between the nodal gap, antiferromagnetism and superconductivity.
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Affiliation(s)
- Yingying Peng
- National Laboratory for Superconductivity, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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