Abstract
Superconducting quantum interference devices (SQUIDs) are accepted as one of the highest magnetic field sensitive probes. There are increasing demands to image local magnetic fields to explore spin properties and current density distributions in a two-dimensional layer of semiconductors or superconductors. Nano-SQUIDs have recently attracting much interest for high spatial resolution measurements in nanometer-scale samples. Whereas weak-link Dayem Josephson junction nano-SQUIDs are suitable to miniaturization, hysteresis in current-voltage (I-V) characteristics that is often observed in Dayem Josephson junction is not desirable for a scanning microscope. Here we report on our development of a weak-link nano-SQUIDs scanning microscope with small hysteresis in I-V curve and on reconstructions of two-dimensional current density vector in two-dimensional electron gas from measured magnetic field.
Highlights
Superconducting quantum interference devices (SQUIDs) are accepted as one of the highest magnetic field sensitive probes
The supercurrent flowing in a SQUID is a periodical function of the flux penetrating the superconducting loop Φ divided by the magnetic flux quantum Φ0 = h/2e = 2.0679 × 10−15 Wb
We present results of imaging of magnetic field created by current in a Hall-bar structure of a GaAs/Al0.3Ga0.7As modulation-doped single heterojunction to evaluate performance of the weak-link scanning nano-SQUID microscope, and report on reconstruction of the two-dimensional current density vector by a Fourier analysis
Summary
Results of mappings of magnetic field created by ac current between the voltage probes 1 and 2 of the Hall-bar structure (Fig. 5(a,b)) at Isample = 70 and 2.8 μA are shown, respectively, at T = 4 K at the applied magnetic field by a superconducting magnet of 0.0 mT using a probe after mechanical polishing. Mappings of magnetic field distribution induced by current in a GaAs/AlxGa1−xAs modulation-doped single heterojunction sample at T = 4 K for current (c) Isample = 70 and (d) 2.8 μA at the applied magnetic field by a superconducting magnet of 0.0 mT using a nano-SQUID probe after mechanical polishing of the tip of the probe. Jx (x, y) may be obtained by using jx ky kx j y
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