Superconductivity

Smith, H. Grayson; Wilhelm, J. O.

doi:10.1103/revmodphys.7.237

Cited by 39 publications

(33 citation statements)

References 25 publications

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“…Within our theory, a superconductor is a 'giant atom' because of its magnetic and electric properties that include charge redistribution [7], and the connection remarked by Spence [4] qualitatively holds. In the conventional theory of superconductivity superconductors have also been described as 'giant atoms' by London [23] and others [24,25] but only with respect to their magnetic properties, hence no implication for the mean inner potential results from it and the connection between mean inner potential and diamagnetic susceptibility does not exist. The fact that within our theory the connection between diamagnetic susceptibility and mean inner potential does exist strongly suggests that small positive phase shifts will onset immediately below T c , as the diamagnetic susceptibility starts to increase due to wavefunction expansion [22].…”

Section: Discussionmentioning

confidence: 99%

Apparent increase in the thickness of superconducting particles at low temperatures measured by electron holography

Hirsch¹

2013

Ultramicroscopy

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We predict that superconducting particles will show an apparent increase in thickness at low temperatures when measured by electron holography. This will result not from a real thickness increase, rather from an increase in the mean inner potential sensed by the electron wave traveling through the particle, originating in expansion of the electronic wavefunction and resulting negative charge expulsion from the interior to the surface of the superconductor, giving rise to an increase in the phase shift of the electron wavefront going through the sample relative to the wavefront going through vacuum. The temperature dependence of the observed phase shifts will yield valuable new information on the physics of the superconducting state of metals. PACS numbers:FIG. 1: Predicted interference micrograph of a spherical superconducting particle of radius 500nm, mean inner potential V0 = 10V , London penetration depth λL = 40nm and lower critical magnetic field Hc1 = 100G with 300kV electrons, twotimes phase amplified. The full lines indicate the contours of constant phase above Tc, the dashed lines at temperatures well below Tc.

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Section: Discussionmentioning

confidence: 99%

Apparent increase in the thickness of superconducting particles at low temperatures measured by electron holography

Hirsch¹

2013

Ultramicroscopy

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“…A similar divergent ⌬C͑H͒ at T c was observed 75 years ago for the type-I superconductor thallium. 29 The C͑T , H͒ behavior observed for single-crystal OsB 2 in Figs. 10͑a͒ and 10͑b͒ is similar to that observed for the materials mentioned above and might suggest that OsB 2 is a type-I superconductor.…”

Section: Heat Capacitymentioning

confidence: 99%

Multigap superconductivity and Shubnikov–de Haas oscillations in single crystals of the layered borideOsB2

et al. 2010

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Single crystals of superconducting OsB 2 ͓T c = 2.10͑5͒ K͔ have been grown using a Cu-B eutectic flux. We confirm that OsB 2 crystallizes in the reported orthorhombic structure ͑space group Pmmn͒ at room temperature. Both the normal and superconducting state properties of the crystals are studied using various techniques. Heat capacity versus temperature C͑T͒ measurements yield the normal state electronic specific heat coefficient ␥ = 1.95͑1͒ mJ/ mol K 2 and the Debye temperature ⌰ D = 539͑2͒ K. The measured frequencies of Shubnikov-de Haas oscillations are in good agreement with those predicted by band structure calculations. Magnetic susceptibility ͑T , H͒, electrical resistivity ͑T͒, and C͑T , H͒ measurements ͑H is the magnetic field͒ demonstrate that OsB 2 is a bulk low-͓͑T c ͒ =2͑1͔͒ type-II superconductor that is intermediate between the clean and dirty limits ͓ ͑͑T =0͒ / ᐉ = 0.97͔͒ with a small upper critical magnetic field H c2 ͑T =0͒ = 186͑4͒ Oe. The penetration depth is ͑T =0͒ = 0.300 m. An anomalous ͑not single-gap BCS͒ T dependence of was fitted by a two-gap model with ⌬ 1 ͑T =0͒ / k B T c = 1.9 and ⌬ 2 ͑T =0͒ / k B T c = 1.25, respectively. The discontinuity in the heat capacity at T c , ⌬C / ␥T c = 1.32, is smaller than the weak-coupling BCS value of 1.43, consistent with the two-gap nature of the superconductivity in OsB 2 . An anomalous increase in ⌬C at T c of unknown origin is found in finite H; e.g., ⌬C / ␥T c Ϸ 2.5 for H Ϸ 25 Oe.

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“…[12] On the other hand, the Bloch theorem states absence of the stationary current in the ground state with no external field. [14,15,16,17,18] Then the above surface current seems inconsistent with this theorem.…”

Section: Introductionmentioning

confidence: 99%

On the Bloch Theorem Concerning Spontaneous Electric Current

Ōhashi

Momoi

1996

J. Phys. Soc. Jpn.

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We study the Bloch theorem which states absence of the spontaneous current in interacting electron systems. This theorem is shown to be still applicable to the system with the magnetic field induced by the electric current. Application to the spontaneous surface current is also examined in detail. Our result excludes the possibility of the recently proposed $d$-wave superconductivity having the surface flow and finite total current.Comment: 12 pages, LaTeX, 3 Postscript figure

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Superconductivity

Cited by 39 publications

References 25 publications

Apparent increase in the thickness of superconducting particles at low temperatures measured by electron holography

Apparent increase in the thickness of superconducting particles at low temperatures measured by electron holography

Multigap superconductivity and Shubnikov–de Haas oscillations in single crystals of the layered borideOsB2

On the Bloch Theorem Concerning Spontaneous Electric Current

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