Magnon Exchange Mechanism of Ferromagnetic Superconductivity

Abstract

The magnon exchange mechanism of ferromagnetic superconductivity (FM-superconductivity) was developed to explain in a natural way the fact that the superconductivity in $UG{e}_2$, $ZrZ{n}_2$ and $URhGe$ is confined to the ferromagnetic phase.The order parameter is a spin anti-parallel component of a spin-1 triplet with zero spin projection. The transverse spin fluctuations are pair forming and the longitudinal ones are pair breaking. In the present paper, a superconducting solution, based on the magnon exchange mechanism, is obtained which closely matches the experiments with $ZrZ{n}_2$ and $URhGe$. The onset of superconductivity leads to the appearance of complicated Fermi surfaces in the spin up and spin down momentum distribution functions. Each of them consist of two pieces, but they are simple-connected and can be made very small by varying the microscopic parameters. As a result, it is obtained that the specific heat depends on the temperature linearly, at low temperature, and the coefficient $\gamma =\frac{C}{T}$ is smaller in the superconducting phase than in the ferromagnetic one. The absence of a quantum transition from ferromagnetism to ferromagnetic superconductivity in a weak ferromagnets $ZrZ{n}_2$ and $URhGe$ is explained accounting for the contribution of magnon self-interaction to the spin fluctuations' parameters. It is shown that in the presence of an external magnetic field the system undergoes a first order quantum phase transition.

9 pages, 7 figures, accepted for publication in Phys.Rev.B

References in corpus (4)

• Pressure dependence of the magnetization in the ferromagnetic superconductor UGe_2
• Strong Enhancement of Superconducting T_c in Ferromagnetic Phases
• A Model for Superconductivity in Ferromagnetic ZrZn2
• Superconductivity near Itinerant Ferromagnetic Quantum Criticality

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• Magnon-mediated superconductivity on ferromagnetic wallpaper fermions
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• Magnon-induced superconductivity in field-cooled spin-1/2 antiferromagnets
• Metamagnetism and tricriticalilty in heavy-fermion ferromagnet URhGe
• Normal metal to ferromagnetic superconductor tunneling