Quantum physicists control supercurrent

August 10, 2006

Netherlands scientists say they've shown that in a quantum-mechanical circuit, the current can be reversed by using a single electron.

The researchers led by Leo Kouwenhoven from the Delft University of Technology created a superconducting quantum interference device, or SQUID, and discovered they could reverse the current by placing an electron on a "weak link" where the current has to jump across a kind of barrier.

In the SQUID made by Kouwenhoven's team the current circulates around a ring-shaped circuit made from microscopic aluminum wire. There are two breaks in the loop, each bridged by wires just 60 nanometres wide and made from the semiconductor indium arsenide. At very low temperatures the aluminum becomes superconducting and the current is carried by pairs of electrons with zero electrical resistance.

The team used electric fields to turn the semiconductor nanowires into "quantum dots" -- isolated islands of electrical charge. Electron pairs can jump to and from the islands, so the supercurrent becomes chopped into discrete parcels of two electrons.

By adding just one electron to the quantum dot the researchers found they could reverse the direction of the supercurrent.

The physics are explained in the journal Nature.

Copyright 2006 by United Press International

Explore further: Electron partitioning process in graphene observed, a world first

Related Stories

A necklace of fractional vortices

October 2, 2015

Researchers at Chalmers University of Technology have arrived at how what is known as time-reversal symmetry can break in one class of superconducting material. The results have been published in the highly ranked Nature ...

New flat transistor defies theoretical limit

October 1, 2015

A team of researchers with members from the University of California and Rice University has found a way to get a flat transistor to defy theoretical limitations on Field Effect Transistors (FETs). In their paper published ...

Engineering researchers produce breakthrough for photography

September 29, 2015

A revolutionary breakthrough is underway at Dartmouth's Thayer School of Engineering, an innovation that may usher in the next generation of light sensing technology with potential applications in scientific research and ...

Recommended for you

Fusion reactors 'economically viable' say experts

October 2, 2015

Fusion reactors could become an economically viable means of generating electricity within a few decades, and policy makers should start planning to build them as a replacement for conventional nuclear power stations, according ...

Iron-gallium alloy shows promise as a power-generation device

September 29, 2015

An alloy first made nearly two decades ago by the U. S. Navy could provide an efficient new way to produce electricity. The material, dubbed Galfenol, consists of iron doped with the metal gallium. In new experiments, researchers ...

Invisibility cloak might enhance efficiency of solar cells

September 30, 2015

Success of the energy turnaround will depend decisively on the extended use of renewable energy sources. However, their efficiency partly is much smaller than that of conventional energy sources. The efficiency of commercially ...

Extending a battery's lifetime with heat

October 1, 2015

Don't go sticking your electronic devices in a toaster oven just yet, but for a longer-lasting battery, you might someday heat them up when not in use. Over time, the electrodes inside a rechargeable battery cell can grow ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.