Nonlinear Nanodevices Using Magnetic Flux Quanta

Abstract

All devices realized so far that control the motion of magnetic flux quanta employ either samples with nanofabricated spatially-asymmetric potentials (which strongly limit controllability), or pristine superconductors rectifying with low-efficiency time-asymmetric oscillations of an external magnetic field. Using layered Bi2Sr2CaCu2O8+delta materials, here we fabricate and simulate two efficient nonlinear superconducting devices with no spatial asymmetry. These devices can rectify with high-efficiency a two-harmonic external current dragging vortices in target directions by changing either the relative phase or the frequency ratio of the two harmonics.

Magnetic field tunable vortex diode made of YBa2Cu3O7−δ Josephson junction asymmetrical arrays

“…13 allows the direction of rectification to be reversed simply by tuning the applied B. Another type of fluxtronic device based on utilizing the temporal asymmetry of applied drives to guide magnetic flux quanta 20,21 has also been successfully implemented [22][23][24] for both Abrikosov vortices (formed in bulk superconducting materials) and Josephson vortices (trapped in a Josephson junction-JJ-formed in a proximity region between two superconductors). Josephson ratchets based on asymmetric current bias configurations have also been fabricated.…”

Crossing lattice vortex pump

“…1). This has been recently verified experimentally [6] for a current of the form J 1 ðtÞ. This time-asymmetric rectification effect originates from the non-linear response of the vortex lattices on the driving current.…”

“…Moreover, these fixed-asymmetry traps must be produced by using expensive experimental techniques, such as lithography or irradiation. The limitations listed above can be successfully overcome [3][4][5][6] for strongly-anisotropic layered superconductors where a magnetic field tilted away from the main crystallographic directions produces two interpenetrating perpendicular vortex lattices [7,8]: a Josephson vortex (JV) lattice between CuO 2 layers and a pancake vortex (PV) stack lattice aligned along the c-axis. The JV lattice induces a symmetric periodic potential U [7] for the lattice of pancake vortex stacks.…”

Harmonic mixing in two coupled qubits: Quantum synchronization via ac drives

“…It is well known that an overdamped particle driven by two harmonic ac signals through the substrate can drift in any desirable direction if frequencies of the two drives are commensurate. This effect known as harmonic mixing [14][15][16][17][18][19][20][21][22] has been already observed in many systems, including pseudorelativistic electrons in graphene, vortices in superconductors [23], nanoparticles driven through a pore [24], current-driven Josephson junctions [25], etc. This suggests an idea that a coupled two-qubit system also should exhibit a harmonic mixing behavior, but in contrast to the usual classical harmonic mixing for overdamped particles, quantum harmonic mixing should be via parametric coupling of two drives in the quantum master equation.…”