Superconductivity and Quantum Phase Transitions in Weak Itinerant Ferromagnets
Abstract
It is argued that the phase transition in low-T_c clean itinerant ferromagnets is generically of first order, due to correlation effects that lead to a nonanalytic term in the free energy. A tricritical point separates the line of first order transitions from Heisenberg critical behavior at higher temperatures. Sufficiently strong quenched disorder suppresses the first order transition via the appearance of a critical endpoint. A semi-quantitative discussion is given in terms of recent experiments on MnSi and UGe_2. It is then shown that the critical temperature for spin-triplet, p-wave superconductivity mediated by spin fluctuations is generically much higher in a Heisenberg ferromagnetic phase than in a paramagnetic one, due to the coupling of magnons to the longitudinal magnetic susceptibility. This qualitatively explains the phase diagram recently observed in UGe_2 and ZrZn_2.
Cite
@article{arxiv.cond-mat/0108443,
title = {Superconductivity and Quantum Phase Transitions in Weak Itinerant Ferromagnets},
author = {T. R. Kirkpatrick and Thomas Vojta and D. Belitz and R. Narayanan},
journal= {arXiv preprint arXiv:cond-mat/0108443},
year = {2017}
}
Comments
10 pp., LaTeX, 5 ps figs., requires World Scientific style files (included), Invited contribution to MB11