Why do so many electrons stay single?

The beauty of superconductivity is that all electrons are paired at very low temperature. However, researchers now discovered that quite a few do stay as single electrons.

Their presence distorts the tiny signals that have to be measured to allow quantum computation and the detection of faint objects in the universe.

In a collaboration between TU Delft and the SRON Netherlands Institute for Space research, Pieter de Visser and colleagues demonstrated that there is a continuous fluctuation of the number of pairs and free electrons, which led to the observation of the unexpected free electrons.

Now the reason of signal distortions has been unraveled, the new question is why those electrons are not paired. The experiment already excludes external sources of energy like cosmic rays, radioactivity and stray light, which suggest a more fundamental reason for the unwillingness of the electrons to bind.

A solution to this puzzle will be crucial to improve qubits, the building blocks of a quantum computer, and to get the ultimate sensitivity for a future generation of astronomical telescopes.

The work summarized here is reported in the manuscript titled: 'Number fluctuations of sparse quasiparticles in a superconductor', LC12997.

Provided by Delft University of Technology