Low-frequency flux noise in current-carrying high critical temperature superconducting films

Kuriki, Shinya; Kawaguchi, Y.; Takahashi, Kenichi; Matsuda, Masaki

doi:10.1063/1.1772877

Cited by 2 publications

(1 citation statement)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, the flux noise picture is more complicated: the noise level depends on the magnetic pre-history, it follows not only the number of trapped vortices, but also the specific spectrum of metastable trapped states. In particular, a long-lived noisy state may occur in a superconducting wire after a pulsed transport current if the current is not small compared to the critical value [43,48].…”

Section: Trapped Magnetic Flux and Related Noisementioning

confidence: 99%

Superconducting atom chips: advantages and challenges

et al. 2008

View full text Add to dashboard Cite

Superconductors are considered in view of applications to atom chip devices. The main features of magnetic traps based on superconducting wires in the Meissner and mixed states are discussed. The former state may mainly be interesting for improved atom optics, while in the latter, cold atoms may provide a probe of superconductor phenomena. The properties of a magnetic side guide based on a single superconducting strip wire placed in an external magnetic field are calculated analytically and numerically. In the mixed state of type II superconductors, inhomogeneous trapped magnetic flux, relaxation processes and noise caused by vortex motion are posing specific challenges for atom trapping. PACS: 37.10.Gh Atom traps and guides 85.25.Am Superconducting device characterization, design, and modeling Progress towards this goal demands the control and reduction of magnetic noise produced by the metallic components of the atom chip. Randomly fluctuating magnetic fields are generated by thermal current noise in the conducting chip elements and reduce the number of trapped atoms (losses), increase their temperature (heating) and lead to a phase uncertainty in the atom's state (decoherence) -see, for example, [1, 2, 3] and references therein. Theoretical analysis of the magnetic noise generated by a normal metal [4,5,6,7] predicts a fast reduction of the lifetime with the decrease of the distance z t between the trapped atom and the metal surface (trap height); this is in excellent agreement with lifetime measurements [8,9,10]. At a trap height less than 10 ÷ 20 µm, thermal magnetic noise exceeds all other harmful influences on the atom cloud (technical noise due to the current supply instability, residual gas collisions, stray magnetic fields) and provides the dominant limit for the lifetime [1,3]. In the last few years, the application of superconducting materials to atom chips has been widely discussed as a perspective to extend the lifetime of cold atoms [7,11,12,13,14]. A recent theoretical estimate [13] of the magnetic noise caused by a superconductor in the Meissner state showed that the lifetime of atoms trapped above a superconducting layer would be, at least, six orders of magnitude longer than above a normal metal in the same geometry. The analysis presented in [14] predicts an atom lifetime of 5000 s at a trap height of 1 µm. For comparison, at the same height in a normal metal trap the lifetime is less than 0.1 s [9]. At larger heights, the lifetime in a superconducting niobium chip can be much larger (up to 10 11 s at temperature T = 4.2 K).Two first realizations of atom chips with superconducting elements have been reported in Refs. [15] and [16]. In both setups, the trapped atoms were 87 Rb. In the experiment by Nirrengarten et al. [15], the current-carrying wires (in "U" and "Z" shape) were made of niobium and operated at about 4.2 K. The obtained atom spin relaxation time was estimated as 115 s. This value is comparable to the best one achieved for atoms trapped near normal-metal wires [17]. In the second ...

show abstract

Section: Trapped Magnetic Flux and Related Noisementioning

confidence: 99%

Superconducting atom chips: advantages and challenges

et al. 2008

View full text Add to dashboard Cite

show abstract

Response of thin-film SQUIDs to applied fields and vortex fields: Linear SQUIDs

Clem

Brandt

2005

Phys. Rev. B

View full text Add to dashboard Cite

In this paper we analyze the properties of a dc SQUID when the London penetration depth λ is larger than the superconducting film thickness d. We present equations that govern the static behavior for arbitrary values of Λ = λ 2 /d relative to the linear dimensions of the SQUID. The SQUID's critical current Ic depends upon the effective flux Φ, the magnetic flux through a contour surrounding the central hole plus a term proportional to the line integral of the current density around this contour. While it is well known that the SQUID inductance depends upon Λ, we show here that the focusing of magnetic flux from applied fields and vortex-generated fields into the central hole of the SQUID also depends upon Λ. We apply this formalism to the simplest case of a linear SQUID of width 2w, consisting of a coplanar pair of long superconducting strips of separation 2a, connected by two small Josephson junctions to a superconducting current-input lead at one end and by a superconducting lead at the other end. The central region of this SQUID shares many properties with a superconducting coplanar stripline. We calculate magnetic-field and current-density profiles, the inductance (including both geometric and kinetic inductances), magnetic moments, and the effective area as a function of Λ/w and a/w.

show abstract

Low-frequency flux noise in current-carrying high critical temperature superconducting films

Abstract: Articles you may be interested inCurrent sharing between the metallic and superconducting layers of high temperature superconductor coated conductors operated above their critical current

Cited by 2 publications

References 21 publications

Superconducting atom chips: advantages and challenges

Superconducting atom chips: advantages and challenges

Response of thin-film SQUIDs to applied fields and vortex fields: Linear SQUIDs

Contact Info

Product

Resources

About