Casimir effect mechanism of pairing between fermions in the vicinity of a magnetic quantum critical point

Original · EN

We consider two immobile spin 1/2 fermions in a two-dimensional magnetic system that is close to the O(3) magnetic quantum critical point (QCP) which separates magnetically ordered and disordered phases. Focusing on the disordered phase in the vicinity of the QCP, we demonstrate that the criticality results in a strong long range attraction between the fermions, with potential V(r) ∝ -1/rν, ν≈ 0.75, where r is separation between the fermions. The mechanism of the enhanced attraction is similar to Casimir effect and corresponds to multi-magnon exchange processes between the fermions. While we consider a model system, the problem is originally motivated by recent establishment of magnetic QCP in hole doped cuprates under the superconducting dome at doping of about 10%. We suggest the mechanism of magnetic critical enhancement of pairing in cuprates.