Spin waves in half-metallic double perovskite magnets via Dyson's method

A new method for treating strongly correlated electronic matter is applied to an idealized model of double exchange magnetism and to the half-metallic double perovskite $Sr_{2}FeMoO_{6}$, a conducting material that is magnetically ordered at room temperature and potentially useful for spintronics. Our method [1] is a supersymmetric generalization of Dyson's analysis of spin waves in ferromagnets wherein quasiparticles are governed by a non-Hermitian Hamiltonian. Using this method, we obtain the spin wave dispersion relation for the idealized model and for the double perovskite material. We also reformulate these problems using a supersymmetric generalization of Schwinger boson mean-field theory. The results will be compared to a semi-classical exact diagonalization Monte-Carlo analysis [2], and broader implications of the method of non-Hermitian quasiparticles will be discussed. [1] Katherine Jones-Smith, Phil. Trans. Roy. Soc. A28, 371 (2012). [2] O. Erten et al., Phys. Rev. Lett. 107, 257201 (2011)