Dynamics of vacancy-induced modes in the non-Abelian Kitaev spin liquid

One of the long-standing open questions in condensed matter physics, which has recently garnered significant attention, is how a quantum spin liquid (QSL) state responds to the various forms of structural disorder that are inevitable in real materials.

Despite numerous theoretical proposals and candidate materials for QSLs over the past half-century, the existence of this exotic magnetic phase remains contentious due to two primary challenges in experimental identification. First, the absence of long-range magnetic order in QSLs results in a featureless ground state, making its characterization largely dependent on the excitation spectrum and dynamical probes. Second, the unavoidable presence of structural disorder in real materials can significantly affect the spin-liquid phase or even lead to its destruction. This underscores the urgent need for a deeper understanding of the effects of disorder in quantum spin liquids.

The Kitaev honeycomb model is an exactly solvable model that hosts QSL phases and holds the potential for realization in transition-metal compounds with strong spin-orbit coupling. The spin fractionalization into locally conserved fluxes and itinerant Majorana fermions underpins the model's exact solvability, even in real-space representation. This characteristic makes the Kitaev model an ideal testbed for studying disorder effects in quantum spin liquids, allowing us to address the aforementioned challenges by enabling the calculation of the energy spectrum and dynamical response without relying on translational invariance.

In this talk, we explore the possibility of utilizing site disorder in providing new spectroscopic signatures of fractionalized Majorana zero mode in the non-Abelian Kitaev spin liquid. Specifically, we theoretically study its dynamics and inelastic response for the scanning tunneling microscopy (STM) around the vacancy position and discover characteristic signatures of fractionalized Majorana excitations.