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Signatures of a topological phase transition in a planar Josephson junction
Authors:
A. Banerjee,
O. Lesser,
M. A. Rahman,
H. -R. Wang,
M. -R. Li,
A. Kringhøj,
A. M. Whiticar,
A. C. C. Drachmann,
C. Thomas,
T. Wang,
M. J. Manfra,
E. Berg,
Y. Oreg,
Ady Stern,
C. M. Marcus
Abstract:
A growing body of work suggests that planar Josephson junctions fabricated using superconducting hybrid materials provide a highly controllable route toward one-dimensional topological superconductivity. Among the experimental controls are in-plane magnetic field, phase difference across the junction, and carrier density set by electrostatic gate voltages. Here, we investigate planar Josephson jun…
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A growing body of work suggests that planar Josephson junctions fabricated using superconducting hybrid materials provide a highly controllable route toward one-dimensional topological superconductivity. Among the experimental controls are in-plane magnetic field, phase difference across the junction, and carrier density set by electrostatic gate voltages. Here, we investigate planar Josephson junctions with an improved design based on an epitaxial InAs/Al heterostructure, embedded in a superconducting loop, probed with integrated quantum point contacts (QPCs) at both ends of the junction. For particular ranges of in-plane field and gate voltages, a closing and reopening of the superconducting gap is observed, along with a zero-bias conductance peak (ZBCP) that appears upon reopening of the gap. Consistency with a simple theoretical model supports the interpretation of a topological phase transition. While gap closings and reopenings generally occurred together at the two ends of the junction, the height, shape, and even presence of ZBCPs typically differed between the ends, presumably due to disorder and variation of couplings to local probes.
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Submitted 10 January, 2022;
originally announced January 2022.
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Self-assembly of liquid crystal block copolymer PEG-b-smectic polymer in pure state and in dilute aqueous solution
Authors:
B. Xu,
R. Pinol,
M. Nono-Djamen,
S. Pensec,
P. Keller,
P. -A. Albouy,
D. Levy,
M. -H. Li
Abstract:
A series of amphiphilic LC block copolymers, in which the hydrophobic block is a smectic polymer poly(4-methoxyphenyl 4-(6-acryloyloxy-hexyloxy)-benzoate) (PA6ester1) and the hydrophilic block is polyethyleneglycol (PEG), were synthesized and characterized. The self-assembly of one of them in both the pure state and the dilute aqueous solution was investigated in detail. Nano-structures in the p…
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A series of amphiphilic LC block copolymers, in which the hydrophobic block is a smectic polymer poly(4-methoxyphenyl 4-(6-acryloyloxy-hexyloxy)-benzoate) (PA6ester1) and the hydrophilic block is polyethyleneglycol (PEG), were synthesized and characterized. The self-assembly of one of them in both the pure state and the dilute aqueous solution was investigated in detail. Nano-structures in the pure state were studied by SAXS and WAXS on samples aligned by a magnetic field. A hexagonal cylindrical micro-segregation phase was observed with a lattice distance of 11.2 nm. The PEG blocks are in the cylinder, while the smectic polymer blocks form a matrix with layer spacing 2.4 nm and layer normal parallel to the long axis of the cylinders. Faceted unilamellar polymer vesicles, polymersomes, were formed in water, as revealed by cryo-TEM. In the lyotropic bilayer membrane of these polymersomes, the thermotropic smectic order in the hydrophobic block is clearly visible with layer normal parallel to the membrane surface.
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Submitted 3 September, 2009;
originally announced September 2009.
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Is the nonlinear Meissner effect unobservable?
Authors:
M. -R. Li,
P. J. Hirschfeld,
P. Woelfle
Abstract:
We examine the effects of nonlocal electrodynamics for a d-wave superconductor on the field dependence of the magnetic penetration depth. The linear field dependence predicted in the local limit, commonly known as the nonlinear Meissner effect, is instead found to be quadratic, $δλ\sim H^2$ for fields below a crossover scale $H^*$. This crossover is shown to be geometry dependent and for most or…
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We examine the effects of nonlocal electrodynamics for a d-wave superconductor on the field dependence of the magnetic penetration depth. The linear field dependence predicted in the local limit, commonly known as the nonlinear Meissner effect, is instead found to be quadratic, $δλ\sim H^2$ for fields below a crossover scale $H^*$. This crossover is shown to be geometry dependent and for most orientations of the screening currents is of the same order as or greater than $H_{c1}$, implying that the nonlinear Meissner effect can not be observed. For special orientations where the current flows along the nodal directions, however, the nonlinear Meissner effect may be recovered.
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Submitted 9 December, 1998; v1 submitted 23 August, 1998;
originally announced August 1998.
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Comment on ``$T$-dependence of the magnetic penetration depth in unconventional superconductors at low temperatures: Can it be linear?"
Authors:
P. J. Hirschfeld,
M. -R. Li,
P. Wölfle
Abstract:
We comment on a recent letter by Schopohl and Dolgov (SD) which raised the possibility that a d-wave superconductor might be thermodynamically unstable in the limit $T\to 0$. The point of our comment is that this instability can be inevitably prevented by the non-local effects.
We comment on a recent letter by Schopohl and Dolgov (SD) which raised the possibility that a d-wave superconductor might be thermodynamically unstable in the limit $T\to 0$. The point of our comment is that this instability can be inevitably prevented by the non-local effects.
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Submitted 31 October, 1998; v1 submitted 5 June, 1998;
originally announced June 1998.