PhD Defense of Leanna Blanche Müller
- PhD defense
Quasiparticle decay induced by spin anisotropies in the frustrated spin ladder system BiCu2PO6
The inorganic compound BiCu2PO6 contains tubelike structures, which are described magnetically by weakly coupled frustrated spin ladders with a finite energy gap. The elementary excitations are triplons of which the degeneracy is lifted due to Dzyaloshinskii-Moriya interactions. In certain regions of the Brillouin zone the lifetime of the triplon excitation modes becomes finite due to the hybridization of the single-triplon with the two-triplon states. In addition, the dispersions of these triplon modes show a striking down-bending before ceasing to exist. In experiment, BiCu2PO6 shows various types of decay processes, which can be caused by different symmetry breaking interactions. In previous studies, we established a minimal model to include all symmetry-allowed interactions, such as the Dzyaloshinskii-Moriya interaction. Based on this minimal model, we show in this thesis that isotropic and anisotropic effects are responsible for noticeable quasiparticle decay and certain down-shifts of the single-triplon energies. The analyses are based on a deepCUT approach for the isotropic case augmented by a perturbative treatment of the anisotropic couplings inducing quasiparticle decay at zero temperature.
Thesis of Leanna Blanche Müller (2021): Quasiparticle decay induced by spin anisotropies in the frustrated spin ladder system BiCu2PO6