Strain Response as a Probe of Spinon Bands in Quantum Spin Liquids

Quantum spin liquids (QSLs) host spin-fractionalized phases with charge-neutral fermionic excitations, either complex or Majorana. A central challenge in the field is to identify experimentally testable signatures of such fractionalization. We show that lattice strain generates a geometric gauge field that couples to these excitations, producing pseudo–Landau levels and a diamagnetic-like response in certain phases. Using the Kitaev model on the honeycomb lattice as an example, we demonstrate that different QSL phases exhibit distinct strain-induced behaviors: Landau quantization and diamagnetic-like strain response in the semimetallic Kitaev spin liquid and gapped chiral spin liquid phases, versus paramagnetic-like strain response without Landau levels in the Majorana metal phase. We propose resonant ultrasound spectroscopy as a practical probe of these signatures.