Seminar : Spectral singularity of spinons in quantum spin ice
Wednesday, October 7, 2020 - 16:00 to 17:00
Prof. Masafumi Udagawa, Department of Physics, Gakushuin University, Japan
Spectral singularity of spinons in quantum spin ice
Fractionalization is one of the most remarkable phenomena in systems with nontrivial topological character -- represented by quantum spin liquids. Due to the coupling to background gauge fields, fractional excitations are endowed with several unusual features absent in conventional quasiparticle. As an example, in chiral spin liquids, non-Abelian statistics emerges, and its application to quantum computation is intensively discussed. In this talk, we explore the aspect of spectral singularity in fractional excitations, by taking quantum spin ice as a model system. We model this system with spin-1/2 quantum XXZ model defined on a pyrochlore lattice and address the dynamics of fractional spinon excitations through the exact diagonalization of finite clusters, as well as the mapping to a network, which we call state graph [1, 2]. The results of two methods agree accurately and the obtained dynamical structure factor shows a signature reflecting the spectral singularity of single spinon, which cannot be captured in the approximation treating spinon as a conventional quasiparticle. The singularity of spectrum would give observable signatures in inelastic neutron scattering experiments. We also present renewed interpretations to several previous theoretical studies on magnetization process.
 M. Udagawa and R. Moessner, Phys. Rev. Lett. 122, 117201 (2019).
 M. Udagawa and R. Moessner, in preparation.
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