Magnon-induced superconductivity in field-cooled spin-1/2 antiferromagnets

Abstract

If, during the preparation, an external magnetic field is applied upon cooling we say it has been field cooled. A novel mechanism for insulator-metal transition and superconductivity in field-cooled spin-$1/2$ antiferromagnets on bcc lattice is discussed. Applying a magnetic field along the sublattice B magnetization, we change the magnetic and transport properties of the material. There is a critical value $H_{cr1}$. When the magnetic field is below the critical one $H<H_{cr1}$ the prepared material is a spin$-1/2$ antiferromagnetic insulator. When $H>H_{cr1}$ the sublattice A electrons are delocalized and the material is metal. There is a second critical value $H_{cr2}>H_{cr1}$. When $H=H_{cr2}$, it is shown that the Zeeman splitting of the sublattice A electrons is zero and they do not contribute to the magnetization of the system. At this quantum partial order point (QPOP) the sublattice B transversal spin fluctuations (magnons) interact with sublattice A electrons inducing spin anti-parallel \emph{p}-wave superconductivity which coexists with magnetism. At zero temperature the magnetic moment of sublattice B electrons is maximal. Below the N\'{e}el temperature $(T_N)$ the gap is approximately constant with a small increase when the system approaches $T_N$. It abruptly falls down to zero at temperatures above $T_N$.