1
|
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.
Collapse
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
| |
Collapse
|
2
|
Novel Electronic State and Superconductivity in the Electron-Doped High-Tc T’-Superconductors. CONDENSED MATTER 2017. [DOI: 10.3390/condmat2030023] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
3
|
Chong TV, Abd-Shukor R. Ultrasonic attenuation anomalies of n-type superconductor Pr2−xCexCuO4. MODERN PHYSICS LETTERS B 2016; 30:1650314. [DOI: 10.1142/s0217984916503140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
Pr[Formula: see text]Ce[Formula: see text]CuO4 ([Formula: see text] = 0 and 0.15) samples were prepared via solid state reaction. Pr2CuO4 sample is insulating while Pr[Formula: see text]Ce[Formula: see text]CuO4 sample exhibited an onset critical temperature, [Formula: see text] of 21 K. The temperature dependences of ultrasonic attenuation in these polycrystalline n-type superconductor Pr[Formula: see text]Ce[Formula: see text]CuO4 ([Formula: see text] = 0 and 0.15) samples have been measured between 80 K and 300 K using longitudinal and shear waves by pulse-echo-overlap method with frequencies between 5 MHz and 10 MHz. For the longitudinal mode, a pronounced attenuation peak around 200 K was observed in Pr2CuO4, but it is not observed in the superconducting material Pr[Formula: see text]Ce[Formula: see text]CuO4. For the shear mode, no pronounced attenuation peaks were observed in the samples. It is suggested that the attenuation peak in the [Formula: see text] = 0 sample at 200 K is due to the weak structural distortion induced by the magnetic transition.
Collapse
Affiliation(s)
- Tet Vui Chong
- Faculty of Information Technology, Mathematics and Sciences, INTI International University, Persiaran Perdana BBN, Putra Nilai, 71800 Nilai, Negeri Sembilan, Malaysia
| | - R. Abd-Shukor
- School of Applied Physics, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia
| |
Collapse
|
4
|
Jiao L, Weng Z, Liu J, Zhang J, Pang G, Guo C, Gao F, Zhu X, Wen HH, Yuan HQ. Evidence for nodeless superconductivity in NdO(1-x)F(x)BiS2 (x = 0.3 and 0.5) single crystals. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:225701. [PMID: 25988300 DOI: 10.1088/0953-8984/27/22/225701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We study the superconducting pairing states of NdO(1-x)F(x)BiS2 (x = 0.3 and 0.5) by measuring the magnetic penetration depth Δλ(T) using the tunnel-diode-oscillator (TDO) technique. An upturn is observed in Δλ(T) as well as the magnetic susceptibility χ(T) in the low-temperature limit, which is attributed to the paramagnetism of Nd ions. After subtracting the paramagnetic contributions, the penetration depth Δλ(T) follows an exponential-type temperature dependence at T ≪ T(c), providing evidence of nodeless superconductivity for NdO(1-x)F(x)BiS2. This is further supported by the analyses of superfluid density ρ(s)(T), which can be well described by a BCS model with an energy gap of Δ(0) ∼ 2.15 k(B)T(c).
Collapse
Affiliation(s)
- Lin Jiao
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310058, People's Republic of China
| | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Voo KK. Antiferromagnetism and superconductivity in an electron-doped two-dimensional t-U-V model. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:275702. [PMID: 21399265 DOI: 10.1088/0953-8984/22/27/275702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The antiferromagnetism (AFM) and superconductivity (SC) in a t-U-V model for an electron-doped two-dimensional square lattice has been investigated with a mean field approximation. Mean field solutions with 2 × 2 unit structures have been sought. The major merit in this study is that all possible superconducting pairings having 2 × 2 unit structures are considered. It has been found that the spin states and orbitals in the superconducting pairing depend on the band filling, and AFM induces a staggered triplet pairing in a system with a d(x(2)-y(2)) orbital singlet SC (dSC). The ratio of the magnitude of the triplet pairing to the magnitude of the singlet pairing has been found to grow monotonically with the antiferromagnetic moment. However, this additional triplet may not have observable effects in many frequently carried out measurements. We have focused on band fillings higher than half-filled. Fundamental quantities including the density of states, local density of states, and single particle spectral weight have been discussed. This study may be related to the electron-doped high-temperature superconducting cuprates, where there have been experimental observations of AFM and SC coexisting, and the nature of the superconducting pairing has been controversial.
Collapse
Affiliation(s)
- Khee-Kyun Voo
- Department of Communication Engineering, Oriental Institute of Technology, Banqiao City, Taipei County 22061, Taiwan.
| |
Collapse
|
6
|
Martin C, Tillman ME, Kim H, Tanatar MA, Kim SK, Kreyssig A, Gordon RT, Vannette MD, Nandi S, Kogan VG, Bud'ko SL, Canfield PC, Goldman AI, Prozorov R. Nonexponential London penetration depth of FeAs-based superconducting RFeAsO(0.9)F(0.1) (R = La, Nd) single crystals. PHYSICAL REVIEW LETTERS 2009; 102:247002. [PMID: 19659038 DOI: 10.1103/physrevlett.102.247002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2009] [Indexed: 05/28/2023]
Abstract
The superconducting penetration depth lambda(T) has been measured in RFeAsO(0.9)F(0.1) (R = La, Nd) single crystals (R-1111). In Nd-1111, we find an upturn in lambda(T) upon cooling and attribute it to the paramagnetism of the Nd ions, similar to the case of the electron-doped cuprate Nd-Ce-Cu-O. After the correction for paramagnetism, the London penetration depth variation is found to follow a power-law behavior, Deltalambda_{L}(T) proportional, variantT;{2} at low temperatures. The same T2 variation of lambda(T) was found in nonmagnetic La-1111 crystals. Analysis of the superfluid density and of penetration depth anisotropy over the full temperature range is consistent with two-gap superconductivity. Based on this and on our previous work, we conclude that both the RFeAsO (1111) and BaFe(2)As(2) (122) families of pnictide superconductors exhibit unconventional two-gap superconductivity.
Collapse
Affiliation(s)
- C Martin
- Ames Laboratory and Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Matsui H, Terashima K, Sato T, Takahashi T, Fujita M, Yamada K. Direct observation of a nonmonotonic dx2-y2- wave superconducting gap in the electron-doped high-Tc superconductor Pr0.89LaCe0.11CuO4. PHYSICAL REVIEW LETTERS 2005; 95:017003. [PMID: 16090646 DOI: 10.1103/physrevlett.95.017003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2004] [Indexed: 05/03/2023]
Abstract
We performed high-resolution angle-resolved photoemission spectroscopy on electron-doped high-Tc superconductor Pr0.89LaCe0.11CuO4 to study the anisotropy of the superconducting gap. The observed momentum dependence is basically consistent with the dx2-y2- wave symmetry, but obviously deviates from the monotonic dx2-y2- gap function. The maximum gap is observed not at the zone boundary, but at the hot spot where the antiferromagnetic spin fluctuation strongly couples to the electrons on the Fermi surface. The present experimental results suggest the spin-mediated pairing mechanism in electron-doped high-Tc superconductors.
Collapse
Affiliation(s)
- H Matsui
- Department of Physics, Tohoku University, Sendai 980-8578, Japan
| | | | | | | | | | | |
Collapse
|
8
|
Darminto D, Smilde HJH, Leca V, Blank DHA, Rogalla H, Hilgenkamp H. Phase-sensitive order parameter symmetry test experiments utilizing Nd(2-x)Ce(x)CuO(4-y)/Nb zigzag junctions. PHYSICAL REVIEW LETTERS 2005; 94:167001. [PMID: 15907157 DOI: 10.1103/physrevlett.94.167001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Indexed: 05/02/2023]
Abstract
Phase-sensitive order parameter symmetry test experiments are presented on the electron-doped high-T(c) cuprate Nd(2-x)Ce(x)CuO(4-y). These experiments have been conducted using zigzag-shaped thin film Josephson structures, in which the Nd(2-x)Ce(x)CuO(4-y) is connected to the low-T(c) superconductor Nb via an Au barrier layer. For the optimally doped as well as for the overdoped Nd(2-x)Ce(x)CuO(4-y), a clear predominant d(x2-y2)-wave behavior is observed at T=4.2 K. Both compounds were also investigated at T=1.6 K, presenting no indications for a change to a predominant s-wave symmetry with decreasing temperature.
Collapse
|
9
|
Luo HG, Xiang T. Superfluid response in electron-doped cuprate superconductors. PHYSICAL REVIEW LETTERS 2005; 94:027001. [PMID: 15698216 DOI: 10.1103/physrevlett.94.027001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2004] [Indexed: 05/24/2023]
Abstract
We propose a weakly coupled two-band model with dx(2)(-y(2)) pairing symmetry to account for the anomalous temperature dependence of superfluid density rho(s) in electron-doped cuprate superconductors. This model gives a unified explanation to the presence of an upward curvature in rho(s) near T(c) and a weak temperature dependence of rho(s) in low temperatures. Our work resolves a discrepancy in the interpretation of different experimental measurements and suggests that the pairing in electron-doped cuprates has predominately dx(2)(-y(2)) symmetry in the whole doping range.
Collapse
Affiliation(s)
- H G Luo
- Institute of Theoretical Physics and Interdisciplinary Center of Theoretical Studies, Chinese Academy of Sciences, P. O. Box 2735, Beijing 100080, China
| | | |
Collapse
|
10
|
Balci H, Greene RL. Anomalous change in the field dependence of the electronic specific heat of an electron-doped cuprate superconductor. PHYSICAL REVIEW LETTERS 2004; 93:067001. [PMID: 15323654 DOI: 10.1103/physrevlett.93.067001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2004] [Indexed: 05/24/2023]
Abstract
We present specific heat measurements on Pr(2-x)CexCuO(4-delta) single crystals which show an unexpected change in the field dependence of the electronic specific heat (Cel) from linear at T = 2 K to nonlinear at T > or = 3 K. We consider several possible explanations for this change and propose, as a possible interpretation, a phase transition in the symmetry of the order parameter from nodal (e.g., d wave) at T > or = 3 K to gapped (e.g., s wave) at T = 2 K. Such a phase transition could be an explanation for the previous conflicting experimental results on the pairing symmetry in the electron-doped cuprates.
Collapse
Affiliation(s)
- Hamza Balci
- Center for Superconductivity Research, Department of Physics, University of Maryland, College Park 20742, USA
| | | |
Collapse
|
11
|
Snezhko A, Prozorov R, Lawrie DD, Giannetta RW, Gauthier J, Renaud J, Fournier P. Nodal order parameter in electron-doped Pr(2-x)CexCuO(4-delta) superconducting films. PHYSICAL REVIEW LETTERS 2004; 92:157005. [PMID: 15169311 DOI: 10.1103/physrevlett.92.157005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2003] [Indexed: 05/24/2023]
Abstract
The London penetration depth, lambda(ab)(T), is reported for thin films of the electron-doped superconductor Pr(2-x)Ce(x)CuO(4-delta) with varying Ce concentration, x=0.13, 0.15, and 0.17. Measurements down to 0.35 K were carried out using a tunnel-diode oscillator with excitation fields applied both perpendicular and parallel to the conducting planes. Films at all three doping levels exhibited power law behavior indicative of d-wave pairing with impurity scattering. These results are fully consistent with previous measurements on single crystals.
Collapse
Affiliation(s)
- A Snezhko
- Department of Physics & Astronomy and NanoCenter, University of South Carolina, 712 Main Street, Columbia, South Carolina 29208, USA
| | | | | | | | | | | | | |
Collapse
|
12
|
Sonier JE, Poon KF, Luke GM, Kyriakou P, Miller RI, Liang R, Wiebe CR, Fournier P, Greene RL. Superconductivity and field-induced magnetism in Pr2-xCexCuO4 single crystals. PHYSICAL REVIEW LETTERS 2003; 91:147002. [PMID: 14611547 DOI: 10.1103/physrevlett.91.147002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2003] [Indexed: 05/24/2023]
Abstract
We report muon-spin rotation and relaxation (muSR) measurements on single crystals of the electron-doped high-T(c) superconductor Pr2-xCexCuO4. In a zero external magnetic field, superconductivity is found to coexist with dilute Cu spins that are static on the muSR time scale. In an applied field, we observe a mu(+)-Knight shift that is primarily due to the magnetic moment induced on the Pr ions. Below the superconducting transition temperature T(c), an additional source of local magnetic field appears throughout the volume of the sample. This finding is shown to be consistent with field-induced antiferromagnetic ordering of the Cu spins. Measurements of the temperature dependence of the in-plane magnetic penetration depth lambda(ab) in the vortex state are also presented.
Collapse
Affiliation(s)
- J E Sonier
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Kim MS, Skinta JA, Lemberger TR, Tsukada A, Naito M. Magnetic penetration depth measurements of Pr2-xCexCuO4-delta films on buffered substrates: evidence for a nodeless gap. PHYSICAL REVIEW LETTERS 2003; 91:087001. [PMID: 14525268 DOI: 10.1103/physrevlett.91.087001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2003] [Indexed: 05/24/2023]
Abstract
We report measurements of the inverse squared magnetic penetration depth, lambda(-2)(T), in Pr(2-x)Ce(x)CuO(4-delta) (0.115< or =x < or =0.152) superconducting films grown on SrTiO3 (001) substrates coated with a buffer layer of insulating Pr2CuO4. lambda(-2)(0), T(c), and normal-state resistivities of these films indicate that they are clean and homogeneous. Over a wide range of Ce doping, 0.124< or =x < or =0.144, lambda(-2)(T) at low T is flat: it changes by less than 0.15% over a factor of 3 change in T, indicating a gap in the superconducting density of states. Fits to the first 5% decrease in lambda(-2)(T) produce values of the minimum superconducting gap in the range of 0.29< or =Delta(min)/k(B)T(c)< or =1.01.
Collapse
Affiliation(s)
- Mun-Seog Kim
- Department of Physics, The Ohio State University, Columbus, OH 43210-1106, USA
| | | | | | | | | |
Collapse
|
14
|
Venturini F, Hackl R, Michelucci U. Comment on "Nonmonotonic d(x2-y2) superconducting order parameter in Nd(2-x)CexCuO4". PHYSICAL REVIEW LETTERS 2003; 90:149701-149702. [PMID: 12731956 DOI: 10.1103/physrevlett.90.149701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2002] [Indexed: 05/24/2023]
|
15
|
Chesca B, Ehrhardt K, Mössle M, Straub R, Koelle D, Kleiner R, Tsukada A. Magnetic-field dependence of the maximum supercurrent of La2-xCexCuO4-y interferometers: evidence for a predominant dx2-y2 superconducting order parameter. PHYSICAL REVIEW LETTERS 2003; 90:057004. [PMID: 12633392 DOI: 10.1103/physrevlett.90.057004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2002] [Indexed: 05/24/2023]
Abstract
We performed a phase-sensitive test of the symmetry of the superconducting order parameter of the electron doped cuprate La(2-x)Ce(x)CuO(4-y) using a superconducting quantum interferometer with spatially distributed Josephson junctions. The studies were made on a thin film grown on a SrTiO3 tetracrystal substrate. The superconducting transition temperature was about 29 K which indicates that the sample is close to optimal doping. The magnetic field dependence of the critical current gives strong evidence for a predominant dx(2)(-y(2)) order parameter symmetry of the sample measured. It also gives upper limits for the s-wave component in a mixed order parameter of the type s+idx(2)(-y(2)).
Collapse
Affiliation(s)
- B Chesca
- Physikalisches Institut-Experimentalphysik II, Universität Tübingen, auf der Morgenstelle 14, Germany
| | | | | | | | | | | | | |
Collapse
|
16
|
Biswas A, Fournier P, Qazilbash MM, Smolyaninova VN, Balci H, Greene RL. Evidence of a d- to s-wave pairing symmetry transition in the electron-doped cuprate superconductor Pr(2-x)CexCuO4. PHYSICAL REVIEW LETTERS 2002; 88:207004. [PMID: 12005593 DOI: 10.1103/physrevlett.88.207004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2001] [Indexed: 05/23/2023]
Abstract
We present point contact spectroscopy (PCS) data for junctions between a normal metal and the electron-doped cuprate superconductor Pr(2-x)CexCuO4 (PCCO). For the underdoped compositions of this cuprate ( x approximately 0.13) we observe a peak in the conductance-voltage characteristics of the point contact junctions. The shape and magnitude of this peak suggest the presence of Andreev bound states at the surface of underdoped PCCO which is evidence for a d-wave pairing symmetry. For overdoped PCCO ( x approximately 0.17) the PCS data do not show any evidence of Andreev bound states at the surface suggesting an s-wave pairing symmetry.
Collapse
Affiliation(s)
- Amlan Biswas
- Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742
| | | | | | | | | | | |
Collapse
|
17
|
Skinta JA, Kim MS, Lemberger TR, Greibe T, Naito M. Evidence for a transition in the pairing symmetry of the electron-doped cuprates La(2-x)Ce(x)CuO(4-y) and Pr(2-x)Ce(x)CuO(4-y). PHYSICAL REVIEW LETTERS 2002; 88:207005. [PMID: 12005594 DOI: 10.1103/physrevlett.88.207005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2001] [Indexed: 05/23/2023]
Abstract
We present measurements of the magnetic penetration depth, lambda(-2)(T), in Pr(2-x)Ce(x)CuO(4-y) and La(2-x)Ce(x)CuO(4-y) films at three Ce doping levels, x, near optimal. Optimal and overdoped films are qualitatively and quantitatively different from underdoped films. For example, lambda(-2)(0) decreases rapidly with underdoping but is roughly constant above optimal doping. Also, lambda(-2)(T) at low T is exponential at optimal and overdoping but is quadratic at underdoping. In light of other studies that suggest both d- and s-wave pairing symmetry in nominal optimally doped samples, our results are evidence for a transition from d- to s-wave pairing near optimal doping.
Collapse
Affiliation(s)
- John A Skinta
- Department of Physics, The Ohio State University, Columbus, Ohio 43210-1106, USA
| | | | | | | | | |
Collapse
|
18
|
Skinta JA, Lemberger TR, Greibe T, Naito M. Evidence for a nodeless gap from the superfluid density of optimally doped Pr(1.855)Ce(0.145)CuO(4-y) films. PHYSICAL REVIEW LETTERS 2002; 88:207003. [PMID: 12005592 DOI: 10.1103/physrevlett.88.207003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2001] [Indexed: 05/23/2023]
Abstract
We present measurements of the ab-plane magnetic penetration depth, lambda(T), in five optimally doped Pr(1.855)Ce(0.145)CuO(4-y) films for 1.6 K< or =T < or =T(c) approximately 24 K. Low resistivities, high superfluid densities n(s)(T) proportional, variant lambda(-2)(T), high T(c)'s, and small transition widths are reproducible and indicative of excellent film quality. For all five films, lambda(-2)(T)/lambda(-2)(0) at low T is well fitted by an exponential temperature dependence with a gap, Delta(min), of 0.85k(B)T(c). This behavior is consistent with a nodeless gap and is incompatible with d-wave superconductivity.
Collapse
Affiliation(s)
- John A Skinta
- Department of Physics, The Ohio State University, Columbus, Ohio 43210-1106, USA
| | | | | | | |
Collapse
|
19
|
Blumberg G, Koitzsch A, Gozar A, Dennis BS, Kendziora CA, Fournier P, Greene RL. Nonmonotonic d(x(2)-y(2)) superconducting order parameter in Nd2-xCexCuO4. PHYSICAL REVIEW LETTERS 2002; 88:107002. [PMID: 11909382 DOI: 10.1103/physrevlett.88.107002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2001] [Indexed: 05/23/2023]
Abstract
Low energy polarized electronic Raman scattering of the electron-doped superconductor Nd2-x Ce x CuO4 ( x = 0.15, T(c) = 22 K) has revealed a nonmonotonic d(x(2)-y(2)) superconducting order parameter. It has a maximum gap of 4.4k(B)T(c) at Fermi surface intersections with an antiferromagnetic Brillouin zone (the "hot spots") and a smaller gap of 3.3k(B)T(c) at fermionic Brillouin zone boundaries. The gap enhancement in the vicinity of the hot spots emphasizes the role of antiferromagnetic fluctuations and the similarity in the origin of superconductivity for electron- and hole-doped cuprates.
Collapse
Affiliation(s)
- G Blumberg
- Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974, USA.
| | | | | | | | | | | | | |
Collapse
|
20
|
Hill RW, Proust C, Taillefer L, Fournier P, Greene RL. Breakdown of Fermi-liquid theory in a copper-oxide superconductor. Nature 2001; 414:711-5. [PMID: 11742390 DOI: 10.1038/414711a] [Citation(s) in RCA: 146] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The behaviour of electrons in solids is well described by Landau's Fermi-liquid theory, which predicts that although electrons in a metal interact, they can still be treated as well defined fermions, which are called 'quasiparticles'. At low temperatures, the ability of quasiparticles to transport heat is given strictly by their ability to transport charge, as described by a universal relation known as the Wiedemann-Franz law, which hitherto no material has been known to violate. High-temperature superconductors have long been thought to fall outside the realm of Fermi-liquid theory, as suggested by several anomalous properties, but this has yet to be shown conclusively. Here we report an experimental test of the Wiedemann-Franz law in the normal state of a copper-oxide superconductor, (Pr,Ce)2CuO4, which reveals that the elementary excitations that carry heat in this material are not fermions. This is compelling evidence for the breakdown of Fermi-liquid theory in high-temperature superconductors.
Collapse
Affiliation(s)
- R W Hill
- Canadian Institute for Advanced Research, Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
| | | | | | | | | |
Collapse
|
21
|
Sato T, Kamiyama T, Takahashi T, Kurahashi K, Yamada K. Observation of d(x2-y2)-like superconducting gap in an electron-doped high-temperature superconductor. Science 2001; 291:1517-9. [PMID: 11222851 DOI: 10.1126/science.1058021] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
High-resolution angle-resolved photoemission spectroscopy of the electron-doped high-temperature superconductor Nd(2-x)Ce(x)CuO4 (x = 0.15, transition temperature T(c) = 22 K) has found the quasiparticle signature as well as the anisotropic d(x2-y2)-like superconducting gap. The spectral line shape at the superconducting state shows a strong anisotropic nature of the many-body interaction. The result suggests that the electron-hole symmetry is present in the high-temperature superconductors.
Collapse
Affiliation(s)
- T Sato
- Department of Physics, Tohoku University, Sendai 980-8578, Japan., Institute for Chemical Research, Kyoto University, Uji 611-0011, Japan
| | | | | | | | | |
Collapse
|
22
|
Armitage NP, Lu DH, Feng DL, Kim C, Damascelli A, Shen KM, Ronning F, Shen ZX, Onose Y, Taguchi Y, Tokura Y. Superconducting gap anisotropy in Nd1.85Ce0.15CuO4: results from photoemission. PHYSICAL REVIEW LETTERS 2001; 86:1126-1129. [PMID: 11178026 DOI: 10.1103/physrevlett.86.1126] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2000] [Indexed: 05/23/2023]
Abstract
We have performed angle resolved photoelectron spectroscopy on the electron doped cuprate superconductor Nd1.85Ce0.15CuO4. A comparison of the leading edge midpoints between the superconducting and normal states reveals a small, but finite shift of 1.5-2 meV near the ( pi,0) position, but no observable shift along the zone diagonal near ( pi/2, pi/2). This is interpreted as evidence for an anisotropic superconducting gap in the electron doped materials, which is consistent with the presence of d-wave superconducting order in this cuprate superconductor.
Collapse
Affiliation(s)
- N P Armitage
- Department of Physics, Applied Physics and Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, California 94305, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Prozorov R, Giannetta RW, Fournier P, Greene RL. Evidence for nodal quasiparticles in electron-doped cuprates from penetration depth measurements. PHYSICAL REVIEW LETTERS 2000; 85:3700-3703. [PMID: 11030985 DOI: 10.1103/physrevlett.85.3700] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2000] [Indexed: 05/23/2023]
Abstract
The in-plane magnetic penetration depth, lambda(T), was measured down to 0.4 K in single crystals of electron-doped superconductors, Pr(1.85)Ce(0.15)CuO(4-delta) (PCCO) and Nd(1.85)Ce(0.15)CuO(4-delta) (NCCO). In PCCO, the superfluid density varies as T2 from 0.025 up to roughly 0.3T/T(c) suggestive of a d-wave state with impurities. In NCCO, lambda(T) shows a pronounced upturn for T<4 K due to the paramagnetic contribution of Nd3+ ions. Fits to an s-wave order parameter over the standard BCS range (T/T(c) = 0.32) limit any gap to less than Delta(min)(0)/T(c) = 0.57 in NCCO. For PCCO, the absence of paramagnetism permits a lower temperature fit and yields an upper limit of Delta(min)(0)/T(c) = 0.2.
Collapse
Affiliation(s)
- R Prozorov
- Loomis Laboratory of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801, USA
| | | | | | | |
Collapse
|