Lecturer: Dr. Yonathan Anahory
Affiliation: Weizmann Institute of Science
Abstract:
NanoSQUIDs residing on the apex of a quartz
tip (SOT), suitable for scanning probe
microscopy with record size, spin sensitivity,
and operating magnetic fields, are presented
[1]. We have developed SOT made of Pb with
an effective diameter of 46 nm and flux noise of
Φn = 50 nΦ0/Hz1/2 at 4.2 K that is operational
up to unprecedented high fields of 1 T [2]. The
corresponding spin sensitivity of the device is
Sn = 0.38 μB/Hz1/2, which is about two orders
of magnitude more sensitive than any other
SQUID to date. A limitation which is common to
all scanning SQUID systems is their sensitivity
to only one component of the magnetic field.
Recently, a new device that is fabricated by
pulling a quartz tube with a “θ” shaped cross
section overcomes this limitation [3]. This
geometry gives rise to two parallel SQUID loops
sharing a common branch. Using a focused ion
beam, we then etch the tip so that the two
SQUID loops become oblique with respect to
each other. As a result of the 3D structure, the
SQUID can be tuned in-situ to be sensitive to
two orthogonal components of the magnetic
field. We use this technique to study vortex
matter in superconductors. At low vortex
density and low currents, we measure the
fundamental dependence of the elementary
pinning force of multiple defects on the vortex
displacement. The outstanding magnetic
sensitivity of the SOT allows probing vortex
displacements as small as 10 pm. This study
reveals rich internal structure of the pinning
potential and unexpected phenomena such as
softening of the restoring force and abrupt
depinning. The results shed new light on the
importance of multi-scale random disorder on
vortex dynamics and thermal relaxation.at high
vortex density and high currents, we image the
flow patterns of moving lattice revealing
dynamic instabilities, plastic flow, and ordering.
[1] A. Finkler, Y. Segev, Y. Myasoedov, M. L.
Rappaport, L. Neeman, D. Vasyukov, E.
Zeldov, M. E. Huber, J. Martin and A. Yacoby,
Nano Lett. 10, 1046 (2010)
[2] D. Vasyukov, Y. Anahory, L. Embon, D.
Halbertal, J. Cuppens, L. Neeman, A. Finkler,
Y. Segev, Y. Myasoedov, M. L. Rappaport, M.
E. Huber, and E. Zeldov, Nature Nanotech. 8,
639 (2013).
[3] Y. Anahory, J. Reiner, L. Embon, D.
Halbertal, A. Yakovenko, Y. Myasoedov, M.L.
Rappaport, M. Huber and E. Zeldov, Nano Lett.
(in press).