Spin-valley half-metal in systems with Fermi surface nesting

Abstract

Half-metals have fully spin polarized charge carriers at the Fermi surface. Such polarization usually occurs due to strong electron--electron correlations. Recently [Phys. Rev. Lett. {\bf{119}}, 107601 (2017)], we have demonstrated theoretically that adding (or removing) electrons to systems with Fermi surface nesting also stabilizes the half-metallic states even in the weak-coupling regime. In the absence of doping, the ground state of the system is a spin or charge density wave, formed by four nested bands. Each of these bands is characterized by charge (electron/hole) and spin (up/down) labels. Only two of these bands accumulate charge carriers introduced by doping, forming a half-metallic two-valley Fermi surface. Analysis demonstrates that two types of such half-metallicity can be stabilized. The first type corresponds to the full spin polarization of the electrons and holes at the Fermi surface. The second type, with antiparallel spins in electron-like and hole-like valleys, is referred to as a "spin-valley half-metal" and corresponds to the complete polarization with respect to the spin-valley operator. We analyze spin and spin-valley currents and possible superconductivity in these systems. We show that spin or spin-valley currents can flow in both half-metallic phases.

14 pages, 5 figures, longer version of arXiv:1704.01727

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Cited by in corpus (8)

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• Can bilayer graphene become a fractional metal?
• Competition of spatially inhomogeneous states in antiferromagnetic Hubbard model
• Half-metal and other fractional metal phases in doped AB bilayer graphene
• Dynamical spin susceptibility of spin-valley half-metal
• Bistability of zigzag edge magnetism in graphene nanoribbons induced by electric field
• Superconductivity and spin density wave in AA stacked bilayer graphene
• Nesting-driven ferromagnetism of itinerant electrons