Antiferromagnetic ordering in arrays of superconducting<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>π</mml:mi></mml:math>-rings

Kirtley, J. R.; Tsuei, C. C.; Ariando, Ariando; Smilde, H.J.H.; Hilgenkamp, H.

doi:10.1103/physrevb.72.214521

Cited by 50 publications

(53 citation statements)

References 44 publications

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“…Unfortunately, these effects are difficult to model or predict, because existing experimental techniques cannot directly observe the local ordering, near lattice defects or otherwise. To address this long outstanding problem, recent interest [9][10][11][12][13][14] has focused on fabricating systems that allow the effects of frustration to be physically modeled and the resulting local configurations to be directly observed.…”

Section: Textmentioning

confidence: 99%

Direct observation of the ice rule in an artificial kagome spin ice

2008

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Abstract:Recently, significant interest has emerged in fabricated systems that mimic the behavior of geometrically-frustrated materials. We present the full realization of such an artificial spin ice system on a two-dimensional kagome lattice and demonstrate rigid adherence to the local ice rule by directly counting individual pseudo-spins. The resulting spin configurations show not only local ice rules and long-range disorder, but also correlations consistent with spin ice Monte Carlo calculations. Our results suggest that dipolar corrections are significant in this system, as in pyrochlore spin ice, and they open a door to further studies of frustration in general. 75.75.+a, 75.50.Lk

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Section: Textmentioning

confidence: 99%

Direct observation of the ice rule in an artificial kagome spin ice

2008

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“…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.…”

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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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“…30 These are one-dimensional chains and two-dimensional arrays of rings. 31,32 A single ring is a superconducting loop consisting of Josephson junctions where there is at least one junction. 33 The phase shift by in such a junction results in the formation of an orbital moment on the ring ͑see for details Ref.…”

Section: Discussionmentioning

confidence: 99%

Fractal structures in systems made of small magnetic particles

Kürten

Kusmartsev

2005

Phys. Rev. B

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We have found that in a system consisting of small magnetic particles a phenomenon related to the formation of fractal structures may arise. The fractal features may arise not only in the distribution of magnetic moments but also in their energy spectrum. The magnetization and the susceptibility of the system also display fractal characteristics. The multiple structures are associated with exponentially many locally stable minima in a highly complex energy landscape. The signature of these fractal structures can be experimentally detected by various methods.

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Antiferromagnetic ordering in arrays of superconductingπ-rings

Cited by 50 publications

References 44 publications

Direct observation of the ice rule in an artificial kagome spin ice

Direct observation of the ice rule in an artificial kagome spin ice

0−πJosephson Tunnel Junctions with Ferromagnetic Barrier

Fractal structures in systems made of small magnetic particles

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