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Spin dynamics within the block orbital-selective Mott phase

Jacek Herbrych, Knoxville, University of Tennessee and ORNL

15.12.2017 at 09:00 

Iron-based superconductors display a variety of magnetic phases originating in the competition
between electronic, orbital, and spin degrees of freedom. Previous theoretical investigations [1]
of the one-dimensional (1D) multiorbital Hubbard model revealed the existence of an orbi tal-
selective Mott phase (OSMP) with ferromagnetic or block spin order. In the later, spins of the
localized orbital form antiferromagnetically coupled ferromagnetic (FM) islands. Recent inelastic
neutron scattering (INS) experiments on quasi -1D BaFe2Se3 and doped RbFe2Se3 compounds confirm the relevance of the spin -block phases [2-4].

Moreover, the INS spectrum unveiled exotic features in the dynamical spin structure factor including a low -
energy  acoustic mode and a high -energy optical mode. In my talk I present the first
theoretical/computational study of the dynamical spin structure factor S(q, omega) within the
block-OSMP using the density-matrix renormalization group method. In agreement with
experimental results we find two modes: a dispersive (acoustic) mode for momentum q< \pi/2
and a dispersion-less (optical) mode for q>\pi/2. The latter is attributed to local block  Hund
excitations, while the former arises from the dynamics of FM islands.

[1] J. Rincon et al., Phy s. Rev. Lett. 112, 106405 (2014)
[2] M. Wang, et al., Nature Comm. 2, 580 (2011)
[3] M. Wang, et al., Phys. Rev. B 94, 041111(R) (2016)
[4] M. Mourigal, et al., Phys. Rev. Lett. 115, 047401 (2015)

A 450, Theresienstr. 37