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Filamentary superconductivity across the phase diagram of Ba(Fe,Co)$_2$As$_2$
Authors:
H. Xiao,
T. Hu,
S. K. He,
B. Shen,
W. J. Zhang,
B. Xu,
K. F. He,
J. Han,
Y. P. Singh,
H. H. Wen,
X. G. Qiu,
C. Panagopoulos,
C. C. Almasan
Abstract:
We show magnetotransport results on Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ ($0.0 \leq x \leq 0.13$) single crystals. We identify the low temperature resistance step at 23 K in the parent compound with the onset of filamentary superconductivity (FLSC), which is suppressed by an applied magnetic field in a similar manner to the suppression of bulk superconductivity (SC) in doped samples. FLSC is found to pe…
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We show magnetotransport results on Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ ($0.0 \leq x \leq 0.13$) single crystals. We identify the low temperature resistance step at 23 K in the parent compound with the onset of filamentary superconductivity (FLSC), which is suppressed by an applied magnetic field in a similar manner to the suppression of bulk superconductivity (SC) in doped samples. FLSC is found to persist across the phase diagram until the long range antiferromagnetic order is completely suppressed. A significant suppression of FLSC occurs for $0.02<x<0.04$, the doping concentration where bulk SC emerges. Based on these results and the recent report of an electronic anisotropy maximum for 0.02 $\leq x \leq$ 0.04 [Science 329, 824 (2010)], we speculate that, besides spin fluctuations, orbital fluctuations may also play an important role in the emergence of SC in iron-based superconductors.
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Submitted 16 August, 2012;
originally announced August 2012.
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Transport Measurements on Nano-engineered Two Dimensional Superconducting Wire Networks
Authors:
W. J. Zhang,
S. K. He,
H. Xiao,
G. M. Xue,
Z. C. Wen,
X. F. Han,
S. P. Zhao,
C. Z. Gu,
X. G. Qiu
Abstract:
Superconducting triangular Nb wire networks with high normal-state resistance are fabricated by using a negative tone hydrogen silsesquioxane (HSQ) resist. Robust magnetoresistance oscillations are observed up to high magnetic fields and maintained at low temperatures, due to the eective reduction of wire dimensions. Well-defined dips appear at integral and rational values (1/2, 1/3, 1/4) of the r…
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Superconducting triangular Nb wire networks with high normal-state resistance are fabricated by using a negative tone hydrogen silsesquioxane (HSQ) resist. Robust magnetoresistance oscillations are observed up to high magnetic fields and maintained at low temperatures, due to the eective reduction of wire dimensions. Well-defined dips appear at integral and rational values (1/2, 1/3, 1/4) of the reduced flux f = Phi/Phi_0, which is the first observation in the triangular wire networks. These results are well consistent with theoretical calculations for the reduced critical temperature as a function of f.
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Submitted 22 March, 2012;
originally announced March 2012.
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Edge superconducting state in Nb thin film with rectangular arrays of antidots
Authors:
W. J. Zhang,
S. K. He,
H. F. Liu,
G. M. Xue,
H. Xiao,
B. H. Li,
Z. C. Wen,
X. F. Han,
S. P. Zhao,
C. Z. Gu,
X. G. Qiu,
Victor V. Moshchalkov
Abstract:
Superconducting Nb thin films with rectangular arrays of submicron antidots have been systemically investigated by transport measurements. In low fields, the magnetoresistance curves demonstrate well-defined dips at integral and rational numbers of flux quanta per unit cell, which corresponds to a superconducting wire network-like regime. When the magnetic field is higher than a saturation field,…
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Superconducting Nb thin films with rectangular arrays of submicron antidots have been systemically investigated by transport measurements. In low fields, the magnetoresistance curves demonstrate well-defined dips at integral and rational numbers of flux quanta per unit cell, which corresponds to a superconducting wire network-like regime. When the magnetic field is higher than a saturation field, interstitial vortices interrupt the collective oscillation in low fields and form vortex sublattice, where a larger magnetic field interval is observed. In higher fields, a crossover behavior from the interstitial sublattice state to a single-loop-like state is observed, characterized by oscillations with a period of $Φ_0/πr_{eff}^2$, originating from the existence of edge superconducting states with a size $r_{eff}$ around the antidots.
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Submitted 1 March, 2012; v1 submitted 1 March, 2012;
originally announced March 2012.
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Abnormal magnetoresistance behavior in Nb thin film with rectangular antidot lattice
Authors:
W. J. Zhang,
S. K. He,
B. H. Li,
F. Cheng,
B. Xu,
Z. C. Wen,
W. H. Cao,
X. F. Han,
S. P. Zhao,
X. G. Qiu
Abstract:
Abnormal magnetoresistance behavior is found in superconducting Nb films perforated with rectangular arrays of antidots (holes). Generally magnetoresistance were always found to increase with increasing magnetic field. Here we observed a reversal of this behavior for particular in low temperature or current density. This phenomenon is due to a strong 'caging effect' which interstitial vortices are…
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Abnormal magnetoresistance behavior is found in superconducting Nb films perforated with rectangular arrays of antidots (holes). Generally magnetoresistance were always found to increase with increasing magnetic field. Here we observed a reversal of this behavior for particular in low temperature or current density. This phenomenon is due to a strong 'caging effect' which interstitial vortices are strongly trapped among pinned multivortices.
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Submitted 11 December, 2011; v1 submitted 16 November, 2011;
originally announced November 2011.
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Wire network behavior in superconducting Nb films with diluted triangular arrays of holes
Authors:
S. K. He,
W. J. Zhang,
H. F. Liu,
G. M. Xue,
B. H. Li,
H. Xiao,
Z. C. Wen,
X. F. Han,
S. P. Zhao,
C. Z. Gu,
X. G. Qiu
Abstract:
We present transport measurement results on superconducting Nb films with diluted triangular arrays (honeycomb and kagomé) of holes. The patterned films have large disk-shaped interstitial regions even when the edge-to-edge separations between nearest neighboring holes are comparable to the coherence length. Changes in the field interval of two consecutive minima in the field dependent resistance…
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We present transport measurement results on superconducting Nb films with diluted triangular arrays (honeycomb and kagomé) of holes. The patterned films have large disk-shaped interstitial regions even when the edge-to-edge separations between nearest neighboring holes are comparable to the coherence length. Changes in the field interval of two consecutive minima in the field dependent resistance $R(H)$ curves are observed. In the low field region, fine structures in the $R(H)$ and $T_c(H)$ curves are identified in both arrays. Comparison of experimental data with calculation results shows that these structures observed in honeycomb and kagomé hole arrays resemble those in wire networks with triangular and $T_3$ symmetries, respectively. Our findings suggest that even in these specified periodic hole arrays with very large interstitial regions, the low field fine structures are determined by the connectivity of the arrays
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Submitted 8 February, 2012; v1 submitted 7 September, 2011;
originally announced September 2011.