Magnetic Breakdown Reshapes Quantum Oscillations in Kagome Metals

Abstract

Recent quantum-oscillation experiments on kagome metals have revealed markedly different phase offsets even among systems with nearly identical band structures and Fermi-surface geometries. Using a tight-binding model, we show that weak orbital hybridization can slightly modify the hybridization gaps. Small variations in these gaps can substantially alter the measured oscillation phase, despite leaving the overall electronic structure nearly unchanged. This phase shift originates from magnetic breakdown, which reconstructs cyclotron trajectories and can mask the nontrivial phase of an isolated orbit, yielding a trivial phase offset. Moreover, uniaxial strain can tune the relevant hybridization gaps and thereby weaken magnetic breakdown. This restores the nontrivial phase offset that magnetic breakdown otherwise masks, providing an experimentally accessible knob for controlling the oscillation phase. These results identify magnetic breakdown as the key mechanism controlling the phase shift and provide a plausible explanation for recent experimental phase discrepancies in kagome metals.