Ultra low noise YBa2Cu3O7−δ nano superconducting quantum interference devices implementing nanowires (original) (raw)
Related papers
Journal of Applied Physics, 2016
We report on measurements of YBa 2 Cu 3 O 7Àd nanowire based Superconducting QUantum Interference Devices (nanoSQUIDs) directly coupled to an in-plane pickup loop. The pickup loop, which is coupled predominantly via kinetic inductance to the SQUID loop, allows for a significant increase of the effective area of our devices. Its role is systematically investigated and the increase in the effective area is successfully compared with numerical simulations. Large effective areas, together with the ultra low white flux noise below 1 lU 0 = ffiffiffiffiffiffi Hz p , make our nanoSQUIDs very attractive as magnetic field sensors. Published by AIP Publishing.
Bicrystal junctions and superconducting quantum interference devices in YBa2Cu3O7 thin films
Journal of Applied Physics, 1994
Josephson junctions and superconducting quantum interference devices (SQUIDS) were made by depositing thin films of YBa,Cu,O, on bicrystal substrates of Y-ZrOz and SrTiOs. The critical current density of the junctions at 77 K could be adjusted from 100 to lo6 A/cm* by selecting bicrystals with misorientation angles 19 from 45" to 0". Current-voltage curves from junctions with 022" followed the resistively shunted junction model with noise rounding close to the transition temperature. The response of the critical current to magnetic fields was Fraunhofer-like and the width (w) dependence was l/w2 due to flux focusing effects. Shapiro steps under microwave radiation were observed. SQUIDS based on these junctions had energy resolutions at 77 K down to 8.6X 10e3' J/Hz and a 10 Hz flux noise level down to 1.5 X 10e9 @Hz at 85 K. A SQUID of the Ketchen design with a flux focusing washer had a magnetic field sensitivity of 15 pT/,iHz at 77 K. The temperature dependence of the voltage modulation depth close to T, was examined and found to be in agreement with theory [K. Enpuku, Y. Shimomura, and T. Kisu, J. Appl. Phys. 73, 7929 (1993)].
Operation of a superconducting nanowire quantum interference device with mesoscopic leads
Physical Review B, 2005
A theory describing the operation of a superconducting nanowire quantum interference device (NQUID) is presented. The device consists of a pair of thin-film superconducting leads connected by a pair of topologically parallel ultra-narrow superconducting wires. It exhibits intrinsic electrical resistance, due to thermally-activated dissipative fluctuations of the superconducting order parameter. Attention is given to the dependence of this resistance on the strength of an externally applied magnetic field aligned perpendicular to the leads, for lead dimensions such that there is essentially complete and uniform penetration of the leads by the magnetic field. This regime, in which at least one of the lead dimensions-length or width-lies between the superconducting coherence and penetration lengths, is referred to as the mesoscopic regime. The magnetic field causes a pronounced oscillation of the device resistance, with a period not dominated by the Aharonov-Bohm effect through the area enclosed by the wires and the film edges but, rather, in terms of the geometry of the leads, in contrast to the well-known Little-Parks resistance of thin-walled superconducting cylinders. A detailed theory, encompassing this phenomenology quantitatively, is developed through extensions, to the setting of parallel superconducting wires, of the Ivanchenko-Zil'berman-Ambegaokar-Halperin theory of intrinsic resistive fluctuations in a current-biased Josephson junctions and the Langer-Ambegaokar-McCumber-Halperin theory of intrinsic resistive fluctuations in superconducting wires. In particular, it is demonstrated that via the resistance of the NQUID, the wires act as a probe of spatial variations in the superconducting order parameter along the perimeter of each lead: in essence, a superconducting phase gradiometer.
Superconducting quantum interference device instruments and applications
Review of Scientific Instruments, 2006
Superconducting quantum interference devices ͑SQUIDs͒ have been a key factor in the development and commercialization of ultrasensitive electric and magnetic measurement systems. In many cases, SQUID instrumentation offers the ability to make measurements where no other methodology is possible. We review the main aspects of designing, fabricating, and operating a number of SQUID measurement systems. While this article is not intended to be an exhaustive review on the principles of SQUID sensors and the underlying concepts behind the Josephson effect, a qualitative description of the operating principles of SQUID sensors and the properties of materials used to fabricate SQUID sensors is presented. The difference between low and high temperature SQUIDs and their suitability for specific applications is discussed. Although SQUID electronics have the capability to operate well above 1 MHz, most applications tend to be at lower frequencies. Specific examples of input circuits and detection coil configuration for different applications and environments, along with expected performance, are described. In particular, anticipated signal strength, magnetic field environment ͑applied field and external noise͒, and cryogenic requirements are discussed. Finally, a variety of applications with specific examples in the areas of electromagnetic, material property, nondestructive test and evaluation, and geophysical and biomedical measurements are reviewed.
Performance of asymmetric superconducting quantum interference devices
Physica C: Superconductivity, 2002
Low T c superconducting quantum interference devices with asymmetric shunt resistances (SQUIDARs) have been numerically and experimentally investigated. Numerical simulations show that the flux to voltage transfer coefficient V U and magnetic flux noise S U are strongly dependent on both the asymmetry parameter q and damping parameter c ¼ R=R d , where R and R d are the SQUID normal resistance and damping resistance, respectively. For small c values, SQUIDARs show larger V U and smaller S U than symmetric devices. Asymmetric SQUIDs can then improve the performance of standard sensors in most of the magnetometric applications. By increasing c, V U several times larger than that of symmetric SQUIDs can be achieved. Therefore, it is possible to couple SQUIDAR magnetometers to an external preamplifier without the need of an external circuit, simplifying the read-out electronics. Experimental values of the magnetic field sensitivity of 6-7 fT/Hz 1=2 have been so far obtained. These results, already suitable for biomagnetic applications, can be further improved by properly optimizing the device parameters. Ó
Macroscopic quantum behavior of superconducting quantum interference devices
Fortschritte der Physik, 2003
Superconducting quantum interference devices (SQUIDs) are made by a superconducting loop interrupted by one or more Josephson junctions. They are described in terms of a macroscopic variable, the magnetic flux, which shows quantum effects such as tunnelling through a potential barrier. Besides making up the source of a quantum state, SQUIDs also provide the instruments necessary for its probing: as a fact, SQUID based magnetometers have a sensitivity approaching the quantum limit. In this paper I will review the working principle of these devices and illustrate the system of SQUIDs realized in my group to test the quantum behavior at a macroscopic level. *
Low-field magnetic response of multi-junction superconducting quantum interference devices
The European Physical Journal B, 2008
The magnetic states of multi-junction superconducting quantum interference device containing 2N identical conventional Josephson junctions are studied by means of a perturbation analysis of the non-linear first-order ordinary differential equations governing the dynamics of the Josephson junctions in these devices. In the zero-voltage state, persistent currents are calculated in terms of the externally applied magnetic flux Φex. The resulting d.c. susceptibility curves show that paramagnetic and diamagnetic states are present, depending on the value of Φex. The stability of these states is qualitatively studied by means of the effective potential notion for the system.