Observation of Chirality Transition of Quasiparticles at Stacking Solitons in Trilayer Graphene

Trilayer graphene (TLG) exhibits rich novel electronic properties and extraordinary quantum Hall phenomena owning to enhanced electronic interactions and tunable chirality of its quasiparticles. Here, we report direct observation of chirality transition of quasiparticles at stacking solitons of TLG via spatial-resolved Landau level spectroscopy. The one-dimensional stacking solitons with width of the order of 10 nm separate adjacent Bernal-stacked TLG and rhombohedral-stacked TLG. By using high field tunneling spectra of scanning tunneling microscopy, we measured Landau quantization in both the Bernal-stacked TLG and the rhombohedral-stacked TLG and, importantly, we observed evolution of quasiparticles between the chiral degree l = 1&2 and l = 3 across the stacking domain wall solitons. Our experiment indicates that such a chirality transition occurs smoothly, accompanying the transition of the stacking orders of TLG, around the domain wall solitons. This result demonstrates the important and hitherto neglected relationship between the crystallographic stacking order and the chirality of quasiparticles in graphene systems.