基于沟槽Dayem纳米桥和磁通变压器的SQUID磁强计

Properties of Grooved Dayem Bridge based YBa$_2$Cu$_3$O$_{7-δ}$ Superconducting Quantum Interference Devices and Magnetometers

The transport properties of a YBa$_2$Cu$_3$O$_{7-δ}$ superconducting quantum interference device (SQUID) based on grooved Dayem bridge weak links are studied as a function of temperature: at high temperatures ($60~$K$<T<T_\mathrm{c}=89$~K) the weak links show properties similar to SNS junctions, while at temperatures below 60~K the weak links behave like short Dayem bridges. Using these devices, we have fabricated SQUID magnetometers with galvanically coupled in-plane pick-up loops: at $T=77$~K, magnetic field white noise levels as low as $63$~fT/$\sqrt{\mathrm{Hz}}$ have been achieved.

Grooved Dayem nanobridges as building blocks of high-performance YBa$_2$Cu$_3$O$_{7-δ}$ SQUID magnetometers

We present noise measurements performed on a YBa$_2$Cu$_3$O$_{7-δ}$ nanoscale weak-link-based magnetometer consisting of a Superconducting QUantum Interference Device (SQUID) galvanically coupled to a $3.5 \times 3.5~$mm$^2$ pick-up loop, reaching white flux noise levels and magnetic noise levels as low as $6~μΦ_0 / \sqrt{\mathrm{Hz}}$ and $100$~fT/$\sqrt{\mathrm{Hz}}$ at $T=77$~K, respectively. The low noise is achieved by introducing Grooved Dayem Bridges (GDBs), a new concept of weak-link. A fabrication technique has been developed for the realization of nanoscale grooved bridges, which sub…

超导 Dayem 纳米桥中的符号反转二极管效应

Sign reversal diode effect in superconducting Dayem nanobridges

本文证明全金属超导 Dayem 纳米桥在外磁场下具有高效非互易超流，并通过调节磁场或温度实现二极管极性反转，揭示其源于高次谐波、涡旋相位及反常相位偏移。

基于3D Dayem纳米桥的单片dc-SQUID中的约瑟夫森二极管效应

Josephson diode effect in monolithic dc-SQUIDs based on 3D Dayem nanobridges

本文提出一种基于3D Dayem纳米桥的单片dc-SQUID超流二极管，通过打破时空对称性实现非互易库珀对输运，最大整流效率约20%，且无需环路电感，易于集成与小型化。

Metastable states and hidden phase slips in nanobridge SQUIDs

We fabricated an asymmetric nanoscale SQUID consisting of one nanobridge weak link and one Dayem bridge weak link. The current phase relation of these particular weak links is characterized by multivaluedness and linearity. While the latter is responsible for a particular magnetic field dependence of the critical current (so-called vorticity diamonds), the former enables the possibility of different vorticity states (phase winding numbers) existing at one magnetic field value. In experiments the observed critical current value is stochastic in nature, does not necessarily coincide with the cur…

Niobium and niobium nitride SQUIDs based on anodized nanobridges made with an Atomic Force Microscope

We present a fabrication method of superconducting quantum interference devices (SQUIDs) based on direct write lithography with an Atomic Force Microscope (AFM). This technique involves maskless local anodization of Nb or NbN ultrathin films using the voltage biased tip of the AFM. The SQUIDs are of weak-link type, for which two geometries have been tested: Dayem and variable thickness nanobridges. The magnetic field dependence of the maximum supercurrent Ic(flux) in resulting SQUIDs is thoroughly measured for different weak link geometries and for both tested materials. It is found that the m…