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EP-4742878-A1 - COMPONENT WITH JOSEPHSON CONTACT, MAGNETIC FIELD SENSOR AND METHOD OF MANUFACTURING

EP4742878A1EP 4742878 A1EP4742878 A1EP 4742878A1EP-4742878-A1

Abstract

The invention relates to a component with a surface having a step separating an upper level (3) of the surface from a lower level (4) of the surface, with superconductors (8, 9, 10) on the surface, wherein a Josephson contact is provided at each edge of the step, wherein each Josephson contact is formed by two superconductors and a barrier (11, 12) between the superconductors (8, 9, 10), characterized in that the critical current of one Josephson contact is greater than the critical current of the other Josephson contact. The invention relates to a magnetic field sensor with the component and a method for its manufacture.

Inventors

  • FALEY, MIKHAIL

Assignees

  • Forschungszentrum Jülich GmbH

Dates

Publication Date
20260513
Application Date
20250917

Claims (15)

  1. Component with a surface having a step separating an upper level (3) of the surface from a lower level (4) of the surface, with superconductors (8, 9, 10) on the surface, wherein a Josephson contact is present at each edge of the step, wherein each Josephson contact is formed by two superconductors and a barrier (11, 12) between the superconductors (8, 9, 10), characterized in that the critical current of one Josephson contact is greater than the critical current of the other Josephson contact.
  2. Component according to the preceding claim, characterized in that the cross-sections of the superconductors (8, 9) at one barrier (11) are larger than the cross-sections of the superconductors (9, 10) at the other barrier (12).
  3. Component according to one of the preceding claims, characterized in that the superconductors (8, 9, 10) consist of single-crystal material.
  4. Component according to the preceding claim, characterized in that the superconductors (8, 9, 10) are formed from YBCO.
  5. Component according to one of the preceding claims, characterized in that the critical current of one Josephson contact is greater by a factor of 5 or by a factor of 10 than the critical current of the other Josephson contact.
  6. Component according to one of the preceding claims, characterized in that the critical current of one Josephson contact at the upper edge of the step is greater than the critical current of the Josephson contact at the lower edge.
  7. Component according to one of the preceding claims, characterized in that the upper plane (3) of the surface is separated from the lower plane (4) of the surface by a plane (5) of the step which forms an angle with the upper plane (3) and with the lower plane (4) which is between 130° and 140° or between 133° and 137° or which is 135°.
  8. Component according to one of the preceding claims, characterized in that the component comprises a single-crystal substrate (2) with a step.
  9. Component according to the preceding claim, characterized in that the substrate (2) consists of MgO.
  10. Component according to one of the two preceding claims, characterized in that a first layer (13) of YBCO is applied to the substrate (2), a second layer (14) of SrTiO 3 is applied to the first layer (13) and a third layer of YBCO is applied to the second layer (14).
  11. Component according to the preceding claim, characterized in that the first layer (13) is thinner than the second layer (14) and that the second layer (14) is thinner than the third layer.
  12. Component according to one of the preceding claims, characterized in that the width (B1) of the superconductors (8, 9) at one barrier (11) is at least 1 µm or at least 2 µm and the width (B2) of the superconductors (9, 10) at the other barrier (12) is not more than 800 nm or not more than 500 nm.
  13. Component according to one of the preceding claims, characterized in that the height of the step is 300 nm to 2000 nm.
  14. Magnetic field sensor with a component (1) according to one of the preceding claims.
  15. Method for producing an object according to one of the preceding claims, in which a layer of superconducting material is applied to a substrate (2) having a step and subsequently the width of the layer is reduced at an edge of the step.

Description

The invention relates to an electronic component with a Josephson contact, a magnetic field sensor with the component, and a method for its manufacture. A Josephson junction is a superconducting structure based on the so-called Josephson effect. The Josephson effect describes the behavior of superconductors that can be separated by a barrier. The barrier can be electrically conductive, weakly superconducting, or an electrical insulator. If the barrier is an insulator, then Cooper pairs (paired electrons or holes) can "tunnel" through this barrier ("tunneling effect"). The barrier can be a grain boundary between two single-crystal superconductors. In this case, current can flow without requiring an external voltage source. A prerequisite for this is that the critical current is not exceeded. The critical current is the maximum current that can flow through a Josephson junction without a voltage drop (the "DC Josephson effect"). If the current flowing through the Josephson junction exceeds the critical current, the junction exhibits electrical resistance (the "AC Josephson effect"). Therefore, an electrical voltage is required for an electric current to flow through the barrier. A superconductor is a material in which an electric current can flow below a certain temperature (the so-called transition temperature T<sub>C</sub> ) without a voltage drop. An electronic component with a Josephson junction is used in quantum technology and precision measurement technology. An electronic component with a Josephson junction enables the construction of superconducting quantum bits (qubits) in quantum computers as well as extremely sensitive magnetic field sensors, so-called SQUIDs (Superconducting Quantum Interference Devices). The barrier of the Josephson junction can be fabricated using a step of a substrate. A superconducting material can be deposited on a step surface in such a way that at least two single-crystal regions are formed, separated by a grain boundary. The single-crystal regions separated by a grain boundary can then form two superconductors. The grain boundary at a The edge of a step can be a barrier to a Josephson contact between the two superconductors. Since a step has two edges, such a component can include two Josephson contacts. A component with one step and two Josephson contacts at the two edges of that step can be disadvantageous for further use, for example, in a magnetic field sensor or as a qubit. From the printed text WO 2013/149607 A1 is an electronic component with a Josephson contact and a method for its manufacture is known. The object of the invention is to further develop a component with a Josephson contact at an edge of a step. In particular, the component should be well suited for use in a magnetic field sensor or for the construction of a qubit. The problem is solved by a component with the features of the first claim. A dependent claim relates to a magnetic field sensor comprising the component. Another dependent claim relates to a manufacturing method. The dependent claims relate to improved embodiments. To solve the problem, a component can include a surface with a step. The step can separate an upper surface level from a lower surface level. Superconductors can be present on the surface. At each edge of the step, there can be a Josephson junction, i.e., a barrier separating two superconductors. The critical current of one Josephson junction can be higher than the critical current of the other Josephson junction. The cross-sectional areas of the superconductors adjacent to one barrier can be larger than those adjacent to the other barrier. A superconducting layer can be reproducibly deposited as a single crystal on a single plane. No barriers are present on this plane. An edge refers to a transition from one plane to another where the deposition of a superconducting material can reproducibly create a grain boundary, and thus a barrier, between two single-crystal superconductors. Such a component with a step and Josephson contacts with sufficiently different critical currents at the edges of the step is suitable for many applications. This is better suited than a component with two nearly identical Josephson contacts at the edges of a step. It can be exploited that the critical current of one Josephson contact is greater than the critical current of the other. The critical currents can differ by a factor of 2 or more. The operating range of the bias current of a device with such a component can be a range close to the lowest critical current. For a given application, particularly in the case of a SQUID, a critical current that is lower than the other critical current should advantageously be at least 10 µA or at least 20 µA to minimize negative effects due to noise. For a given application, particularly in the case of a SQUID, a critical current that is lower than the other critical current should advantageously be no more than 200 µA, no more than 100 µA, or preferably no mo