Synopsis: Vortices Queue Up in a Nanowire

An applied field can control the entry and exit of single quanta of magnetic flux in superconducting nanowires.
Synopsis figure
N. Marković/Johns Hopkins University

In the 1990s, physicists studying nanoscopic semiconductors found the material’s resistance oscillated up and down with increasing voltage. The oscillations occur because electrons repel each other, and in a sufficiently small device, this repulsion is big enough that the entry of each additional electron onto the device measurably affects its resistance, an effect known as Coulomb blockade. Researchers led by Nina Marković at Johns Hopkins University, Maryland, have now measured a similar repulsive effect between the tiny quanta of magnetic flux (vortices) that become trapped in superconductors in an external field. The observation of the effect, known as Weber blockade, could inspire devices that use vortices, instead of charge, to carry information.

Vortices are defects in a superconductor that form when the material can no longer fully expel the flux from an external magnetic field. Although they are electrically neutral, vortices, like charges, can repel each other. And in nanoscopic wires with a certain geometry, the energy to add a single vortex becomes sizable. Though hints of this Weber blockade effect have been seen experimentally, they weren’t conclusive.

The superconducting wires Marković and her colleagues studied were flat strips of aluminum, less than a 100 nanometers wide and several micrometers long. Superconductors become resistive when the current passed through them exceeds a “critical” value. Marković and her colleagues found that this critical current rose up and down, like regularly spaced mountain peaks, every time they raised an external magnetic field by roughly 50 gauss. These current oscillations are consistent with what’s expected for the entry and exit of a single vortex. The scheme can thus precisely control the number of vortices in the wires, a feature that could be used to build logical devices.

This research is published in Physical Review Letters.

–Jessica Thomas


More Features »


More Announcements »

Subject Areas


Previous Synopsis


Quantum Bending of Light

Read More »

Next Synopsis

Biological Physics

Pulling on a Cell’s Strings

Read More »

Related Articles

Focus: How to Study a Speck of Dust

Focus: How to Study a Speck of Dust

A new technique allows the capture and study of a single dust particle just 34 nanometers wide, nearly 10 times smaller than the previous limit. Read More »

Synopsis: Putting a Spin on the Josephson Effect

Synopsis: Putting a Spin on the Josephson Effect

Researchers demonstrate spin splitting of localized electronic states, called Andreev bound states, in a superconducting device. Read More »

Viewpoint: Pushing Towards Room-Temperature Superconductivity
Condensed Matter Physics

Viewpoint: Pushing Towards Room-Temperature Superconductivity

Two independent studies report superconductivity at record high temperatures in hydrogen-rich materials under extreme pressure. Read More »

More Articles