The observation of gapped quasiparticles near the metal–insulator transition in image Original Research Article

Utilizing high-resolution photoemission spectroscopy (ARPES) with fine-tuned polarization selection we present a systematic study of the insulating cobaltates. A single-particle gap opening is observed, suggesting an anisotropic particle–hole instability is present due to the materialʹs unique topology. Unlike conventional density waves, charge stripes or band insulators, the onset of the gap depends on the quasiparticleʹs quantum coherence, which occurs well below the symmetry breaking temperature of the crystal.