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           Josephson junctions for programmable voltage standards

Schulze, H.; Behr, R.; Müller, F.; Niemeyer, J.

doi:10.1063/1.122064

Cited by 118 publications

(72 citation statements)

References 11 publications

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“…The magnetic dipoledipole interaction is much stronger than for alkalis and may lead to to a BCS-like transition in a degenerate Fermi gas of 53 Cr [17]. In addition, chromium has technological potential in nanostructure fabrication [18,19] and structured doping [20] [14]. To our knowledge, the lifetime τ D of these metastable states has not been measured to date but a lower limit of τ D > 50 s can be deduced from our MT decay times.…”

Section: Fig 1 Relevant Part Of Thementioning

confidence: 85%

“…The magnetic dipoledipole interaction is much stronger than for alkalis and may lead to to a BCS-like transition in a degenerate Fermi gas of 53 Cr [17]. In addition, chromium has technological potential in nanostructure fabrication [18,19] and structured doping [20] by atom lithography.Magneto-optical trapping of chromium is performed on the 7 S 3 → 7 P 4 transition (vacuum wavelength λ PS = 425.6 nm, decay rate Γ PS = 31.5 × 10 6 s −1 , saturation intensity I s = 8.5 mW/cm 2 , FIG. 1).…”

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confidence: 99%

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Continuous loading of a magnetic trap

et al. 2001

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We have realized a scheme for continuous loading of a magnetic trap (MT).52 Cr atoms are continuously captured and cooled in a magneto-optical trap (MOT). Optical pumping to a metastable state decouples atoms from the cooling light. Due to their high magnetic moment (6 µB), low-field seeking metastable atoms are trapped in the magnetic quadrupole field provided by the MOT. Limited by inelastic collisions between atoms in the MOT and in the MT, we load 10 8 metastable atoms at a rate of 10 8 atoms/s below 100 µK into the MT. Optical repumping after the loading allows us to realize a MT of ground state chromium atoms. Although multiply loading of a MT has been achieved [10] experiments so far suffer from the absence of a method for efficient cw loading of atoms into a BEC. Hence to date a matter wave analogon to the continuous wave optical laser has not been realized. Alternatively, a cw atom laser based on magnetic guiding in combination with atomic collisions was suggested [11]. In addition, cw loading of low-dimensional optical traps with laser cooled atoms was proposed [12] and recently demonstrated [13].In this letter we report on the cw loading of a three dimensional conservative trap with laser cooled atoms that are decoupled from all light fields present. We show that atoms can be optically pumped within a chromium magneto-optical trap (MOT) [14,15] into metastable "dark" states and stored in a MT built up by the quadrupole magnetic field of the MOT. We present results of systematic studies on the loading process and on the lifetime of the MT. Using the cw loading mechanism and a final repumping process we obtain good starting conditions for experiments towards degenerate quantum gases with ground state chromium atoms.Our cw loading scheme consists of an atomic reservoir and a conservative trap overlapped in space and time. The reservoir is prepared by cooling atoms in a MOT on a transition |g → |e (FIG. 1). A weak decay channel |e → |d allows the transfer of reservoir atoms into an additional long lived and trapped state |d in which atoms can be accumulated. In our realization low field seeking Zeeman substates of |d are trapped in the magnetic quadrupole field of the MOT. The loading can be very efficient if |d atoms are decoupled from the MOT light and if their kinetic energy is smaller than the conservative trap depth. A large decay rate branching ratio (Γ eg /Γ ed ≫ 1) assures a steady state MOT in thermal equilibrium and is expected to greatly reduce reabsorption of transfer photons by atoms in the MT [16]. MT FIG. 1. Relevant part of the52 Cr level scheme. The MOT involves all levels and transitions, the continuous loading process of the magnetic trap (MT) relies on the Λ-system depicted in black (levels |g , |e , |d ).Chromium combines the desired Λ-like level scheme (FIG. 1, black levels and transitions) with a high magnetic moment of up to 6 µ B (µ B =Bohr's magneton). Due to its isotopic composition (3 bosons:52 Cr (84%), 50 Cr (4%), 54 Cr (2%), and one fermion: 53 Cr (10%) ) it is a promising e...

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Section: Fig 1 Relevant Part Of Thementioning

confidence: 85%

“…The magnetic dipoledipole interaction is much stronger than for alkalis and may lead to to a BCS-like transition in a degenerate Fermi gas of 53 Cr [17]. In addition, chromium has technological potential in nanostructure fabrication [18,19] and structured doping [20] by atom lithography.Magneto-optical trapping of chromium is performed on the 7 S 3 → 7 P 4 transition (vacuum wavelength λ PS = 425.6 nm, decay rate Γ PS = 31.5 × 10 6 s −1 , saturation intensity I s = 8.5 mW/cm 2 , FIG. 1).…”

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confidence: 99%

Continuous loading of a magnetic trap

et al. 2001

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“…The applications of Josephson Junctions (JJs) range from sensors for ultralow magnetic fields and weak electromagnetic radiation [3], millimeter wave resonators [4], programmable voltage standards [5], superconducting flux qubits [6], etc. The physics of JJs changes remarkably when the barrier material is a ferromagnet [7,8].…”

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confidence: 99%

Robust coupling of superconducting order parameter in a mesoscale NbN–Fe–NbN epitaxial structure

Bose

Budhani

2009

Applied Physics Letters

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“…A successful development has been SINIS junctions consisting of a multilayer superconductor-insulator-normal metal-insulator-superconductor originally investigated for electronic applications (Maezawa & Shoji, 1997;Sugiyama et al, 1997). The first small series arrays and 1 V arrays were subsequently fabricated (Schulze et al, 1998;Behr et al, 1999). The 1 V arrays contain 8,192 junctions.…”

Section: Programmable Voltage Standards Based On Binary-divided Arraysmentioning

confidence: 99%