Superconducting quantum interference device without Josephson junctions

Burlakov, A. A.; Гуртовой, В. Л.; Il’in, A. I.; Nikulov, A. V.; Tulin, V. A.

doi:10.1134/s0021364014030059

Cited by 19 publications

(24 citation statements)

References 11 publications

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“…The overlap of the black and red curves is consistent with the physical symmetry of the system: Reversing the direction of the current and the applied field at the same time should produce no change to the system. both the direction of applied current and the direction of the magnetic field will reproduce the initial untransformed state [15]. We illustrate the symmetry transformation on Device 51215s3, in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Nanowire networks [12] and loops [13][14][15][16][17][18][19][20] are qualitatively distinct from conventional Josephson junction and SQUIDS due to the linear nature of the nanowire CPR [13]. In contrast, conventional Josephson junctions obey a sinusoidal CPR.…”

Section: Introductionmentioning

confidence: 98%

“…We also observe that the general shape of the I C (B) curve is made of linear segments rather than being sinusoidal. At temperatures much lower than T C , a linear CPR (and therefore a linear relationship between critical current and field) is both expected [2,[26][27][28][29] and has been observed experimentally [13,15,[22][23][24]. Advanced computational simulations based on Ginzburg-Landau theory, which is known to be valid at temperatures near the critical temperature T C [30], have been used to simulate the critical current versus field dependence of nanowire loops previously [22,24,25].…”

Section: Introductionmentioning

confidence: 99%

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Asymmetric nanowire SQUID: Linear current-phase relation, stochastic switching, and symmetries

Murphy

Bezryadin

2017

Phys. Rev. B

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We study nanodevices based on ultrathin superconducting nanowires connected in parallel to form nanowire SQUIDs. The function of the critical current versus magnetic field, IC (B), is multivalued, asymmetric and its maxima and minima are shifted from the usual integer and half integer flux quantum points. The nanowire interference device is qualitatively distinct from conventional SQUIDs because nanowires do not obey the same current-phase relationship (CPR) as Josephson junctions. We demonstrate that the results can be explained assuming that (i) the CPR is linear and (ii) that each wire is characterized by a sample-specific critical phase, which is usually much larger than π/2. Our proposed model offers accurate fits to IC (B). It explains the single-valuedness regions where only one vorticity (i.e., the order parameter winding number) is stable as well as regions where multiple vorticity values are allowed for the SQUIDs. We also observe and explain regions in which the standard deviation of the switching current is independent of the magnetic field. We develop a technique that allows a reliable detection of hidden phase-slips. Using this technique we find that our model correctly predicts the boundaries of vorticity regions, even at low currents where IC (B) is not directly measurable.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Asymmetric nanowire SQUID: Linear current-phase relation, stochastic switching, and symmetries

Murphy

Bezryadin

2017

Phys. Rev. B

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“…A few designs of small SQUIDs without Josephson junctions have been proposed, based on mesoscopic superconducting loops7, asymmetric superconducting rings8, inhomogeneous superconductors9, constrictions in the superconducting rim10, interrupted mesoscopic normal loop in contact with two superconducting electrodes11, and a combination of superconducting and metallic contact banks12. SQUIDs without Josephson junctions may offer advantages in simplicity of fabrication, and, under certain conditions, a steeper dependence of the measured quantities on the magnetic flux8. The present study may offer a different approach in designing a SQUID without Josephson junctions by switching a nano-ring with two arms into a SQUID using a large enough bias current.…”

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confidence: 99%

Current-induced SQUID behavior of superconducting Nb nano-rings

Sharon

Shaulov

Berger

et al. 2016

Sci Rep

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The critical temperature in a superconducting ring changes periodically with the magnetic flux threading it, giving rise to the well-known Little-Parks magnetoresistance oscillations. Periodic changes of the critical current in a superconducting quantum interference device (SQUID), consisting of two Josephson junctions in a ring, lead to a different type of magnetoresistance oscillations utilized in detecting extremely small changes in magnetic fields. Here we demonstrate current-induced switching between Little-Parks and SQUID magnetoresistance oscillations in a superconducting nano-ring without Josephson junctions. Our measurements in Nb nano-rings show that as the bias current increases, the parabolic Little-Parks magnetoresistance oscillations become sinusoidal and eventually transform into oscillations typical of a SQUID. We associate this phenomenon with the flux-induced non-uniformity of the order parameter along a superconducting nano-ring, arising from the superconducting leads (‘arms’) attached to it. Current enhanced phase slip rates at the points with minimal order parameter create effective Josephson junctions in the ring, switching it into a SQUID.

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“…The theory predicts the jump of the critical current with the n change at Φ = (n + 0.5)Φ 0 not only of the double contour interferometer but also, for example, of a superconducting ring with asymmetric link-up of current leads. A simple magnetometer based on the latter prediction was proposed in [20]. But measurements of aluminium ring with asymmetric link-up of current leads have revealed that a smooth change of its critical current is observed at Φ ≈ (n + 0.5)Φ 0 instead of the jump which must be observed due to the change of the quantum number from n to n+1 [21].…”

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confidence: 99%

Development of a Superconducting Differential Double Contour Interferometer

et al. 2017

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We study operation of a new device, the superconducting differential double contour interferometer (DDCI), in application for the ultra sensitive detection of magnetic flux and for digital read out of the state of the superconducting flux qubit. DDCI consists of two superconducting contours weakly coupled by Josephson Junctions. In such a device a change of the critical current and the voltage happens in a step-like manner when the angular momentum quantum number changes in one of the two contours. The DDCI may outperform traditional Superconducting Quantum Interference Devices when the change of the quantum number occurs in a narrow magnetic field region near the half of the flux quantum due to thermal fluctuations, quantum fluctuations, or the switching a loop segment in the normal state for a while by short pulse of an external current. Higher sensitivity of DDCI compared to the conventional SQUID is provided by strong discreteness of the energy spectrum of the continuous superconducting loop [6]. According to the conventional theory [7] the total energy of the persistent currentin a loop with small cross section s ≪ λ 2 L (T ) is determined mainly by the kinetic energy [8]:L /s)L is the kinetic inductance of the loop of side l; L ≈ µ 0 l is the magnetic inductance; s is the cross section of superconducting wires; n s is the density of the Cooper pairs;is the London penetration depth. Two permitted states n and n + 1 have equal energy at Φ = (n + 0.5)Φ 0 according to (2) and thus equal probability P ∝ exp(−E k /k B T ). The probability of other permitted states is negligible and P (n+1) ≈ 1−P (n) at Φ ≈ (n+0.5)Φ 0 when Φ 2 0 /2L k = I p,A Φ 0 ≫ k B T . The probability of the n state may be described with the relationat the magnetic flux Φ = (n + 0.5)Φ 0 + δΦ, when δΦ ≪ Φ 0 . Here I p,A = Φ 0 /2L k is the persistent current (1) at |n − Φ/Φ 0 | = 1/2 and ǫ = I p,A Φ 0 /k B T . The probability (3) changes from P (n) ≈ 1 to P (n) ≈ 0 in a region of the magnetic flux from δΦ ≈ −Φ 0 /2ǫ to δΦ ≈ Φ 0 /2ǫ. This region may be very narrow due to a big value ǫ = I p,A Φ 0 /k B T ≫ 1 equal, for example ǫ ≈ 1500 at the temperature of measurement T ≈ 1 K and a typical value I p,A = 10 µA measured, for example in [9]. Measurements [10] of flux qubit (superconducting loop with three

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Superconducting quantum interference device without Josephson junctions

Cited by 19 publications

References 11 publications

Asymmetric nanowire SQUID: Linear current-phase relation, stochastic switching, and symmetries

Asymmetric nanowire SQUID: Linear current-phase relation, stochastic switching, and symmetries

Current-induced SQUID behavior of superconducting Nb nano-rings

Development of a Superconducting Differential Double Contour Interferometer

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