Probing Fractionalized Excitations in Kitaev Magnets

Quantum spin liquids are exotic magnetic states in which strong interactions and frustration prevent conventional ordering even at zero temperature. Instead, spins fractionalize into emergent degrees of freedom, giving rise to novel quasiparticles and gauge fields with no direct analog in ordinary magnets. The Kitaev model provides a rare and exactly solvable example of such a phase, hosting itinerant Majorana fermions coupled to a static Z2 gauge field, and has become a central paradigm in the search for quantum spin liquids in real materials.

In this colloquium, I will discuss recent theoretical progress in understanding how fractionalized excitations in Kitaev candidate materials can be detected through experimentally accessible probes. I will first focus on spectroscopic signatures associated with lattice dynamics, showing how phonons and their coupling to spins can serve as sensitive probes of fractionalized degrees of freedom in quantum spin liquids. I will then turn to the role of disorder and defects, which are unavoidable in real materials. Rather than simply obscuring quantum spin liquid behavior, such imperfections can generate distinctive signatures of fractionalization, including localized Majorana modes, enhanced low-energy spectral weight, and unconventional thermodynamic responses.