Macroscopic Quantum Interference in Superconductors

Jaklevic, R. C.; Lambe, John; Mercereau, J. E.; Silver, A. H.

doi:10.1103/physrev.140.a1628

Cited by 245 publications

(72 citation statements)

References 20 publications

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“…4, a plot of J e max as a function of Φ ring is depicted. It exhibits a profile similar to the one observed in experiments [28], showing peaks separated by Φ 0 .…”

Section: Macroscopic Quantum Interferencesupporting

confidence: 63%

“…5, the oscillation of the maximum zero-voltage current with varying an external magnetic field in a circuit with two identical SIS junctions (the SQUID structure) is examined. We show that the present theory explains observed oscillation patterns [28]. We also demonstrate that the "0-SQUID (or edge-junction)" and "π -SQUID (or cornerjunction)" patterns [29] that are usually attributed to the dwave symmetry of the order parameter, are shown to arise from evenness or oddness of the winding number of the Berry phase.…”

Section: Introductionmentioning

confidence: 57%

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Spin-vortex Superconductivity

Koizumi

2011

J Supercond Nov Magn

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We present a theory of superconductivity based on the theoretical prediction that a macroscopic persistent current is generated by spin-vortices. It explains the origin of the phase variable θ that is canonical conjugate to the superfluid density as a Berry phase arising from the spin-vortex formation. This superconductivity does not require Cooperpairs as charge carriers, thus, is not directly related to the standard theory based on the BCS one; however, it exhibits the flux quantization in the unit Φ 0 = hc/2|e|, where h is Planck's constant, c the speed of light, and e the electron charge; and the AC Josephson frequency, f J = 2|e|V /h, where V is the voltage of the battery connected to the superconductor-insulator-superconductor junction. In due course, it is found that the standard derivation of the AC Josephson frequency misses a term arising from the flow of particles through the leads connected to the junction. If this contribution is included, the observed f J indicates that the phase θ is a variable conjugate to the number density of charge e carriers instead of the currently accepted charge 2e carriers. We propose an experiment that discriminates whether it is e or 2e. If the above claim is verified, it means that the BCS theory cannot predict whether a particular compound is a superconductor or not since it does not explain the origin of θ . A connection between the present mechanism and the BCS mechanism is discussed; the fact that the BCS theory gives an excellent estimate of T c is attributed to the fact that it predicts the temperature at which spin-vortices become long-lived due to the energy gap formation; since the stabilization by the electron-pair formation is compatible with the present mechanism, asymmetries observed in the H. Koizumi ( ) Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan e-mail: koizumi@ims.tsukuba.ac.jp even and odd number of electron systems are preserved. The most notable difference is that the persistent current generation is formulated in a strictly particle-number-conserving manner. Thus, it does not violate the superselection rule for the total charge.

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“…4, a plot of J e max as a function of Φ ring is depicted. It exhibits a profile similar to the one observed in experiments [28], showing peaks separated by Φ 0 .…”

Section: Macroscopic Quantum Interferencesupporting

confidence: 63%

Section: Introductionmentioning

confidence: 57%

Spin-vortex Superconductivity

Koizumi

2011

J Supercond Nov Magn

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“…The BQPs play an essential role in characterizing the superconducting state via quantities such as the superconducting gap and its symmetry. Despite the excellent description of the BQPs in BCS theory, there has been no direct experimental observation of the predicted full energy dispersion (electron and hole branches) of BQPs, although the pairing of electrons is evidenced by ac Josephson-junction experiment [4]. For high-T c cuprates, the direct observation of the BQPs is even more significant, since many microscopic ideas of BCS theory have been seriously challenged.…”

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confidence: 99%

BCS-Like Bogoliubov Quasiparticles in High-TcSuperconductors Observed by Angle-Resolved Photoemission Spectroscopy

et al. 2003

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We performed high-resolution angle-resolved photoemission spectroscopy on triple-layered high-Tc cuprate Bi2Sr2Ca2Cu3O 10+δ . We have observed the full energy dispersion (electron and hole branches) of Bogoliubov quasiparticles and determined the coherence factors above and below EF as a function of momentum from the spectral intensity as well as from the energy dispersion based on BCS theory. The good quantitative agreement between the experiment and the theoretical prediction suggests the basic validity of BCS formalism in describing the superconducting state of cuprates.PACS numbers: 74.72. Hs, 74.20Fg, 79.60.Bm It is well known that BCS (Bardeen, Cooper, and Schrieffer) theory [1] explains many of fundamental thermodynamic, transport and magnetic properties of superconductors by introducing a simple picture that two electrons with opposite momenta and spins near the Fermi surface form a pair (Cooper pair) in the superconducting state. In the language of Fermi liquids [2], the quasiparticles (QPs) of the Cooper pairs are called Bogoliubov quasiparticles (BQPs) [3] which are defined as excitation of a single electron "dressed" with an attractive interaction between paired electrons. The BQPs play an essential role in characterizing the superconducting state via quantities such as the superconducting gap and its symmetry. Despite the excellent description of the BQPs in BCS theory, there has been no direct experimental observation of the predicted full energy dispersion (electron and hole branches) of BQPs, although the pairing of electrons is evidenced by ac Josephson-junction experiment [4]. For high-T c cuprates, the direct observation of the BQPs is even more significant, since many microscopic ideas of BCS theory have been seriously challenged. Since the BQPs are a natural consequence of the starting Hamiltonian including the two-body attractive interaction assumed by BCS theory [1], the existence of BQPs would prove the validity of the basic BCS description of the superconducting state in the cuprates.In this Letter, we report the direct observation of BQPs in triple-layered high-T c cuprate Bi 2 Sr 2 Ca 2 Cu 3 O 10+δ by angle-resolved photoemission spectroscopy (ARPES). By using ultrahigh resolution in energy and momentum, we have succeeded in directly observing the full energy dispersion (electron and hole branches) of BQPs below and above the Fermi level (E F ). We have determined experimentally the coherence factors as a function of momentum from ARPES intensity and compared the result with the prediction from BCS theory to investigate the basic

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“…The critical current of a planar rectangular Josephson junction shows a Fraunhofer pattern as a function of the applied magnetic field [12] (see Fig. 1(c)).…”

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confidence: 99%

Interference between magnetic field and cavity modes in an extended Josephson junction

2012

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An extended Josephson junction consists of two superconducting electrodes that are separated by an insulator and it is therefore also a microwave cavity. The superconducting phase difference across the junction determines the supercurrent as well as its spatial distribution. Both, an external magnetic field and a resonant cavity intrafield produce a spatial modification of the superconducting phase along the junction. The interplay between these two effects leads to interference in the critical current of the junction and allows us to continuously tune the coupling strength between the first cavity mode and the Josephson phase from 1 to −0.5 . This enables static and dynamic control over the junction in the ultra-strong coupling regime.

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Macroscopic Quantum Interference in Superconductors

Cited by 245 publications

References 20 publications

Spin-vortex Superconductivity

Spin-vortex Superconductivity

BCS-Like Bogoliubov Quasiparticles in High-TcSuperconductors Observed by Angle-Resolved Photoemission Spectroscopy

Interference between magnetic field and cavity modes in an extended Josephson junction

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