Three decades of research have culminated in what researchers believe is the most convincing evidence yet for magnetism as the force that facilitates unconventional superconductivity. The findings of the study, which was carried out by researchers from Rice University, the Max Planck Institute for Chemical Physics of Solids (MPI-CPfS), and other institutions, were published online in Nature Physics.
Unconventional superconductivity was discovered in 1979, but without today’s techniques and experimental knowledge, researchers struggled to explain the phenomenon.
“In 1979, there was not much understanding of quantum criticality or of the collective way that electrons behave at the border of magnetism,” said Rice physicist Qimiao Si, lead theorist and co-author of the paper published in Nature Physics. “Today, we know a great deal about such collective behavior in the regime where materials transition to a superconducting state. The question we examined in this study is, how does all of that new knowledge translate into an understanding of the superconducting state itself?”
These new experimental techniques were carried out on the same material used in 1979 , a heavy fermion material that is a mix of cerium, copper and silicon, and consisted of bombarding heavy fermion samples with neutrons to probe the spins states of the material’s electrons.
“Our neutron-scattering data provide convincing evidence that the cerium-based heavy fermion compound is located near a quantum critical point,” said Oliver Stockert, one of the study’s authors. “Moreover, the data revealed how the magnetic spectrum changes as the material turns into a superconductor.”
While the study’s authors acknowledge that more studies are needed, Si is confident that the study gives proof that “collective fluctuations of the electrons at the border of magnetism are capable of driving superconductivity.”
[Source: Rice University]
