Special CPM Seminar

Magnetic field-induced antiferromagnetism in superconducting CeCoIn₅

Ilya Vekhter

Louisiana State University

In many correlated electron materials different ordering phenomena compete and, occasionally, coexist. One well studied example of such cohabitation is between antiferromagnetism and superconductivity: the two phenomena coexist in a region of parameter space for several families of unconventional superconductors. The case of heavy fermion CeCoIn₅ has challenged our understanding since this is the only case where antiferromagnetism appears under an applied magnetic field in the superconducting state, but vanishes as soon as superconductivity is suppressed.

After reviewing various scenarios for this observation and comparing them with the experimental data, I will present a theory of the coexistence of superconductivity (SC) and antiferromagnetism (AFM) in CeCoIn₅. I will show that in Pauli-limited superconductors with zeroes (nodes) in the energy gap the nesting of the quasiparticle pockets induced by Zeeman pair breaking leads to incommensurate antiferromagnetic state. I will show that salient features of this theory are in agreement with experiments, and will predict a new double-Q magnetically ordered phase.