<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">d</mml:mi></mml:math>-Wave Induced Zero-Field Resonances in dc<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">π</mml:mi></mml:math>-Superconducting Quantum Interference Devices

Chesca, Boris; Schulz, Robert; Goetz, B.; Schneider, Claudia; Hilgenkamp, H.; Mannhart, J.

doi:10.1103/physrevlett.88.177003

Cited by 25 publications

(14 citation statements)

References 30 publications

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“…• GBJs have demonstrated that the SQUID-dynamics can be altered by the d-wave order parameter in YBCO [30]. It is however important to point out that our results do not directly relate to e.g.…”

Section: Though (4) Is Only Explicitly Solvable In the Limitmentioning

confidence: 65%

Dynamical Effects of an Unconventional Current-Phase Relation in YBCO dc SQUIDs

et al. 2003

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The predominant d-wave pairing symmetry in high temperature superconductors allows for a variety of current-phase relations in Josephson junctions, which is to a certain degree fabrication controlled. In this letter we report on direct experimental observations of the effects of a non-sinusoidal current-phase dependence in YBCO dc-SQUIDs, which agree with the theoretical description of the system.

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Section: Though (4) Is Only Explicitly Solvable In the Limitmentioning

confidence: 65%

Dynamical Effects of an Unconventional Current-Phase Relation in YBCO dc SQUIDs

et al. 2003

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“…(2). In essence our I c (B) data are the same as for 0-π JJs based of d-wave superconductors such as corner JJs [31], bi-, triand tetra-crystal JJs [32,33], and YBCO-Nb or NCCO-Nb ramp zigzag JJs [34,35]. This is not suprising since the underlaying model [18,19,20] is the same.…”

mentioning

confidence: 66%

“…In any case the ground state is degenerate, i.e. may have positive or negative spontaneously formed fractional flux (clockwise or counterclockwise circulating supercurrent) and can be considered as two states (up and down) of a macroscopic spin.Before, 0-π JJs were realized using d-wave superconductors [31,32,33,34,35], the semifluxons spontaneously formed at the 0-π boundary were observed [36,37,38,39], and I c (B) with a minimum at an external magnetic field B = 0 was measured [31,34,35]. However, the phase shift of π in such structures takes place not inside the barrier, but inside the d-wave superconductor.…”

mentioning

confidence: 99%

0−πJosephson Tunnel Junctions with Ferromagnetic Barrier

Weides¹,

et al. 2006

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We fabricated high quality Nb/Al 2 O 3 /Ni 0.6 Cu 0.4 /Nb superconductor-insulator-ferromagnet-superconductor Josephson tunnel junctions. Using a ferromagnetic layer with a step-like thickness, we obtain a 0-π junction, with equal lengths and critical currents of 0 and π parts. The ground state of our 330 µm (1.3λ J ) long junction corresponds to a spontaneous vortex of supercurrent pinned at the 0-π step and carrying ∼ 6.7% of the magnetic flux quantum Φ 0 . The dependence of the critical current on the applied magnetic field shows a clear minimum in the vicinity of zero field. PACS numbers: 74.50.+r, In his classical paper[1] Brian Josephson predicted that the supercurrent through a Josephson junction (JJ) is given by I s = I c sin(µ). Here, µ is the Josephson phase (the difference of phases of the quantum mechanical wave functions describing the superconducting condensate in the electrodes), and I c > 0 is the critical current (maximum supercurrent that one can pass through the JJ). When one passes no current (I s = 0), the Josephson phase µ = 0 corresponds to the minimum of energy (ground state). The solution µ = π corresponds to the energy maximum and is unstable. Later it was suggested that using a ferromagnetic barrier one can realize JJs where. Such junctions obviously have µ = π in the ground state and, therefore, are called π JJs. The solution µ = 0 corresponds to the energy maximum and is unstable.π JJs were recently realized using superconductor-ferromagnet-superconductor (SFS) [3,4,5,6], superconductorinsulator-ferromagnet-superconductor (SIFS) [7] and other [8] technologies. In these junctions the sign of the critical current and, therefore, the phase µ (0 or π) in the ground state, depends on the thickness d F of the ferromagnetic layer and on temperature T [9]. π JJs may substantially improve parameters of various classical and quantum electronic circuits [10,11,12,13,14,15]. To use π JJs not only as a "phase battery", but also as an active (switching) element in various circuits it is important to have a rather high characteristic voltage V c (defined e.g. as V at I = 1.2I c ) and low damping. For example, for classical single flux quantum logic circuits V c defines the speed of operation. For qubits the value of a quasi-particle resistance R qp at V = 0 should be high enough since it defines the decoherence time of the circuits. Both high values of R qp and V c can be achieved by using tunnel SIFS JJs rather than SFS JJs. The dissipation in SIFS JJs decreases exponentially at low temperatures [16], thus, making SIFS technology an appropriate candidate for creating low decoherence quantum circuits, e.g., π qubits. [13,14,15].Actually, the most interesting situation is when one half of the JJ (x < 0) behaves as a 0 JJ, and the other half (x > 0) as a π JJ (a 0-π JJ) [17]: In the symmetric case (equal critical currents and lengths of 0 and π parts) the ground state of such a 0-π JJ corresponds to a spontaneously formed vortex of supercurrent circulating around the 0-π boundary, generating magnetic...

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“…A lot of effort is focused on enhancing the sensitivity and minimizing the noise in SQUID systems (see [3] and references therein). Recently, π/2-and π-SQUIDs based on d-wave superconductors have been investigated as the possible candidates for SQUIDs without the external flux bias [4,5,6]. Soft ferromagnetic materials have been used as another means to improve the sensitivity of SQUID magnetometers [7,8,9].…”

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confidence: 99%

Linear magnetic flux amplifier

Golubović

Moshchalkov

2005

Applied Physics Letters

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By measuring the critical current versus the applied magnetic field I c (Φ) of an Al superconducting loop enclosing a soft Permalloy magnetic dot, we demonstrate that it is feasible to design a linear magnetic flux amplifier for applications in superconducting quantum interference devices. The selected dimensions of a single-domain Permalloy dot provide that the preferential orientation of the magnetization is rotated from the perpendicular direction. By increasing an applied magnetic field, the magnetization of the dot coherently rotates towards the out-of-plane direction, thus providing a flux gain and an enhancement of the sensitivity. As a result of a pronounced shape anisotropy, the flux gain generated by the dot can be tuned by adjusting the dimensions of the dot.

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d-Wave Induced Zero-Field Resonances in dcπ-Superconducting Quantum Interference Devices

Cited by 25 publications

References 30 publications

Dynamical Effects of an Unconventional Current-Phase Relation in YBCO dc SQUIDs

Dynamical Effects of an Unconventional Current-Phase Relation in YBCO dc SQUIDs

0−πJosephson Tunnel Junctions with Ferromagnetic Barrier

Linear magnetic flux amplifier

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