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Nigro A, Guarino A, Leo A, Grimaldi G, Avitabile F, Romano P. Point-Contact Spectroscopy in Bulk Samples of Electron-Doped Cuprate Superconductors. MATERIALS (BASEL, SWITZERLAND) 2023; 16:7644. [PMID: 38138787 PMCID: PMC10744691 DOI: 10.3390/ma16247644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 12/06/2023] [Accepted: 12/08/2023] [Indexed: 12/24/2023]
Abstract
Point-contact spectroscopy was performed on bulk samples of electron-doped high temperature superconductor Nd2-xCexCuO4-δ. The samples were characterized using X-ray diffraction and scanning electron microscopy equipped with a wavelength-dispersive spectrometer and an electron backscatter diffraction detector. Samples with Ce content x = 0.15 showed the absence of spurious phases and randomly oriented grains, most of which had dimensions of approximately 220 µm2. The low-bias spectra in the tunneling regime, i.e., high-transparency interface, exhibited a gap feature at about ±5 meV and no zero-bias conductance, despite the random oriented grains investigated within our bulk samples, consistent with most of the literature data on oriented samples. High-bias conductance was also measured in order to obtain information on the properties of the barrier. A V-shape was observed in some cases, instead of the parabolic behavior expected for tunnel junctions.
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Affiliation(s)
- Angela Nigro
- Physics Department “E. R. Caianiello”, University of Salerno, 84084 Fisciano (Salerno), Italy;
- CNR-SPIN, c/o University of Salerno, 84084 Fisciano (Salerno), Italy; (A.G.); (A.L.); (G.G.); (F.A.)
| | - Anita Guarino
- CNR-SPIN, c/o University of Salerno, 84084 Fisciano (Salerno), Italy; (A.G.); (A.L.); (G.G.); (F.A.)
| | - Antonio Leo
- CNR-SPIN, c/o University of Salerno, 84084 Fisciano (Salerno), Italy; (A.G.); (A.L.); (G.G.); (F.A.)
| | - Gaia Grimaldi
- CNR-SPIN, c/o University of Salerno, 84084 Fisciano (Salerno), Italy; (A.G.); (A.L.); (G.G.); (F.A.)
| | - Francesco Avitabile
- CNR-SPIN, c/o University of Salerno, 84084 Fisciano (Salerno), Italy; (A.G.); (A.L.); (G.G.); (F.A.)
- Department of Sciences and Technologies, Sannio University, 82100 Benevento, Italy
| | - Paola Romano
- CNR-SPIN, c/o University of Salerno, 84084 Fisciano (Salerno), Italy; (A.G.); (A.L.); (G.G.); (F.A.)
- Department of Sciences and Technologies, Sannio University, 82100 Benevento, Italy
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Li Y, Tabis W, Tang Y, Yu G, Jaroszynski J, Barišić N, Greven M. Hole pocket-driven superconductivity and its universal features in the electron-doped cuprates. SCIENCE ADVANCES 2019; 5:eaap7349. [PMID: 30746483 PMCID: PMC6358316 DOI: 10.1126/sciadv.aap7349] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 10/02/2018] [Indexed: 05/10/2023]
Abstract
After three decades of intensive research attention, the emergence of superconductivity in cuprates remains an unsolved puzzle. One major challenge has been to arrive at a satisfactory understanding of the unusual metallic "normal state" from which the superconducting state emerges upon cooling. A second challenge has been to achieve a unified understanding of hole- and electron-doped compounds. Here, we report detailed magnetoresistance measurements for the archetypal electron-doped cuprate Nd2-x Ce x CuO4+δ that, in combination with previous data, provide crucial links between the normal and superconducting states and between the electron- and hole-doped parts of the phase diagram. The characteristics of the normal state (magnetoresistance, quantum oscillations, and Hall coefficient) and those of the superconducting state (superfluid density and upper critical field) consistently indicate two-band (electron and hole) features and point to hole pocket-driven superconductivity in these nominally electron-doped materials. We show that the approximate Uemura scaling between the superconducting transition temperature and the superfluid density found for hole-doped cuprates also holds for the small hole component of the superfluid density in electron-doped cuprates.
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Affiliation(s)
- Yangmu Li
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
- Corresponding author. (Y.L.); (N.B.); (M.G.)
| | - W. Tabis
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
- AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, 30-059 Krakow, Poland
| | - Y. Tang
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - G. Yu
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - J. Jaroszynski
- National High Magnetic Field National Laboratory, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA
| | - N. Barišić
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
- Institute of Solid State Physics, TU Wien, 1040 Vienna, Austria
- Department of Physics, Faculty of Science, University of Zagreb, HR-10000 Zagreb, Croatia
- Corresponding author. (Y.L.); (N.B.); (M.G.)
| | - M. Greven
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
- Corresponding author. (Y.L.); (N.B.); (M.G.)
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Evolution of electronic states in n-type copper oxide superconductor via electric double layer gating. Sci Rep 2016; 6:26642. [PMID: 27221198 PMCID: PMC4879525 DOI: 10.1038/srep26642] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 05/06/2016] [Indexed: 11/12/2022] Open
Abstract
The occurrence of electrons and holes in n-type copper oxides has been achieved by chemical doping, pressure, and/or deoxygenation. However, the observed electronic properties are blurred by the concomitant effects such as change of lattice structure, disorder, etc. Here, we report on successful tuning the electronic band structure of n-type Pr2−xCexCuO4 (x = 0.15) ultrathin films, via the electric double layer transistor technique. Abnormal transport properties, such as multiple sign reversals of Hall resistivity in normal and mixed states, have been revealed within an electrostatic field in range of −2 V to + 2 V, as well as varying the temperature and magnetic field. In the mixed state, the intrinsic anomalous Hall conductivity invokes the contribution of both electron and hole-bands as well as the energy dependent density of states near the Fermi level. The two-band model can also describe the normal state transport properties well, whereas the carrier concentrations of electrons and holes are always enhanced or depressed simultaneously in electric fields. This is in contrast to the scenario of Fermi surface reconstruction by antiferromagnetism, where an anti-correlation is commonly expected.
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Zhang HY, Zhou Y, Lin HQ, Gong CD. Commensurate magnetic excitations induced by band splitting and Fermi surface topology in n-type cuprates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:155603. [PMID: 23507793 DOI: 10.1088/0953-8984/25/15/155603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The antiferromagnetic correlation plays an important role in high-Tc superconductors. Considering this effect, the magnetic excitations in n-type cuprates near the optimal doping are studied within the spin-density-wave description. The magnetic excitations are commensurate in the low-energy regime and further develop into spin-wave-like dispersion at higher energy, consistent with the inelastic neutron scattering measurements. We clearly demonstrate that the commensurability originates from the band splitting and Fermi surface topology. The commensurability is a normal state property and has nothing to do with d-wave superconductivity. Our results strongly suggest the essential role of antiferromagnetic correlations in the cuprates.
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Affiliation(s)
- H Y Zhang
- National Laboratory of Solid State Microstructure, Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
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Voo KK. Order and excitation in partially Gutzwiller projected t-t'-t"-J-U models. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:495602. [PMID: 22101308 DOI: 10.1088/0953-8984/23/49/495602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Extended t-t'-t"-J-U models in which the second-nearest-neighbor hopping (t') and third-nearest-neighbor hopping (t") are included are studied using renormalized mean field theory. The models are meant to be low-energy effective models for the Hubbard models, and hence the Heisenberg exchange integral J and Hubbard repulsion U are related by J = 4t(2)/U. The trial wavefunctions for the ground states are partially Gutzwiller projected Hartree-Fock states. The Gutzwiller projection is implemented by means of a Gutzwiller approximation, and the site double occupancy d is taken as a variational parameter. It is found that a large |t'/t| narrows the band filling range that sustains antiferromagnetism (AFM) in the ground state, enhances the d-wave singlet superconductivity (dSC) in hole overdoped systems, but suppresses the dSC in electron overdoped systems. For a system that has large |t'/t| and |t"/t'|, the superconductivity (SC) at the onset of AFM in hole doped band filling is strongly suppressed. On the excitation occurring, when an electron doped system simultaneously contains SC and AFM, the system is found to have a nodeless gap at the Fermi level. Finally, the result of this study is related to experiments on the superconducting cuprates.
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Affiliation(s)
- Khee-Kyun Voo
- Department of Communication Engineering, Oriental Institute of Technology, Banqiao Area, New Taipei City 22061, Taiwan.
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Santander-Syro AF, Ikeda M, Yoshida T, Fujimori A, Ishizaka K, Okawa M, Shin S, Liang B, Zimmers A, Greene RL, Bontemps N. Two-Fermi-surface superconducting state and a nodal d-wave energy gap of the electron-doped Sm1.85Ce0.15CuO(4-δ) cuprate superconductor. PHYSICAL REVIEW LETTERS 2011; 106:197002. [PMID: 21668192 DOI: 10.1103/physrevlett.106.197002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Indexed: 05/30/2023]
Abstract
We report on laser-excited angle-resolved photoemission spectroscopy in the electron-doped cuprate Sm1.85Ce0.15CuO(4-δ). The data show the existence of a nodal hole-pocket Fermi surface both in the normal and superconducting states. We prove that its origin is long-range antiferromagnetism by an analysis of the coherence factors in the main and folded bands. This coexistence of long-range antiferrmagnetism and superconductivity implies that electron-doped cuprates are two-Fermi-surface superconductors. The measured superconducting gap in the nodal hole pocket is compatible with a d-wave symmetry.
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Chen CP, Jiang HM, Li JX. Coexistence of the antiferromagnetic and superconducting order and its effect on spin dynamics in electron-doped high-T(c) cuprates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:035701. [PMID: 21386294 DOI: 10.1088/0953-8984/22/3/035701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In the framework of the slave-boson approach to the t-t'-t''-J model, it is found that for electron-doped high- T(c) cuprates, the staggered antiferromagnetic (AF) order coexists with the superconducting (SC) order in a wide doping level ranged from underdoped to nearly optimally doped at the mean-field level. In the coexisting phase, it is revealed that the spin response is commensurate in a substantial frequency range below a crossover frequency ω(c) for all dopings considered, and it switches to the incommensurate structure when the frequency is higher than ω(c). This result is in agreement with the experimental measurements. Comparison of the spin response between the coexisting phase and the pure SC phase with a d(x(2)-y(2))-wave pairing plus a higher harmonics term (DP+HH) suggests that the inclusion of the two-band effect is important to consistently account for both the dispersion of the spin response and the non-monotonic gap behavior in the electron-doped cuprates.
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Affiliation(s)
- Cui-Ping Chen
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
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Liu B. Spin-resolved impurity resonance states in electron-doped cuprate superconductors. PHYSICAL REVIEW B 2009; 79:172501. [DOI: 10.1103/physrevb.79.172501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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Ren C, Wang ZS, Luo HQ, Yang H, Shan L, Wen HH. Evidence for two energy gaps in superconducting Ba0.6K0.4Fe2As2 single crystals and the breakdown of the Uemura plot. PHYSICAL REVIEW LETTERS 2008; 101:257006. [PMID: 19113747 DOI: 10.1103/physrevlett.101.257006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2008] [Indexed: 05/27/2023]
Abstract
We report a detailed investigation on the lower critical field H{c1} of the superconducting Ba0.6K0.4Fe2As2 (122) single crystals. A pronounced kink is observed on the H{c1}(T) curve, which is attributed to the existence of two superconducting gaps. By fitting the data H{c1}(T) to the two-gap BCS model in the full temperature region, a small gap of Delta{a}(0)=2.0+/-0.3 meV and a large gap of Delta{b}(0)=8.9+/-0.4 meV are obtained. The in-plane penetration depth lambda{ab}(0) is estimated to be 105 nm corresponding to a rather large superfluid density, which points to the breakdown of the Uemura plot in 122 superconductors.
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Affiliation(s)
- Cong Ren
- National Laboratory for Superconductivity, Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China.
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Das T, Markiewicz RS, Bansil A. Nodeless d-wave superconducting pairing due to residual antiferromagnetism in underdoped Pr2-xCexCuO4-delta. PHYSICAL REVIEW LETTERS 2007; 98:197004. [PMID: 17677653 DOI: 10.1103/physrevlett.98.197004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Indexed: 05/16/2023]
Abstract
We investigate the doping dependence of the penetration depth versus temperature in electron-doped Pr(2-x)Ce(x)CuO(4-delta) using a model which assumes the uniform coexistence of (mean-field) antiferromagnetism and superconductivity. Despite the presence of a d(x2-y2) pairing gap in the underlying spectrum, we find nodeless behavior of the low-T penetration depth in the underdoped case, in accord with experimental results. As doping increases, a linear-in-T behavior of the penetration depth, characteristic of d-wave pairing, emerges as the lower magnetic band crosses the Fermi level and creates a nodal Fermi surface pocket.
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Affiliation(s)
- Tanmoy Das
- Physics Department, Northeastern University, Boston, MA 02115, USA
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