Research: Evidence for an unusual quantum phase transition
Quantum phase transitions are usually associated with a broken symmetry in condensed matter physics. Researchers from Uppsala University, Jan Rusz and Peter Oppeneer, as a part of an international collaboration, find now evidence for a quantum phase transition without symmetry breaking in an unconventional superconductor material, CeCoIn5.
CeCoIn5 is a prototypical strongly correlated material that exhibits an unconventional superconducting phase at low temperatures. A lot of research efforts have been invested into understanding its properties. This is partly motivated by its similarities with an important class of high-temperature superconducting materials – copper oxides.
The new study has revealed a previously unobserved quantum phase transition in CeCoIn5, unaccompanied by any symmetry breaking. In this transition, some of the system's electrons change their behavior from localized to delocalized. One of the possible explanations of the observed unusual properties is based on so called fractionalized Fermi liquid theory, which proposes that under certain conditions the spin and charge of electrons can behave as separated.
The results of this research may have implications for obtaining a deeper understanding of the cuprate superconductors. The article has been published in journal Science.
N. Maksimovic et al., Evidence for a delocalization quantum phase transition
without symmetry breaking in CeCoIn5, Science 374 (2021). Publication date: December 2, 2021