Dimensional crossover and band topology evolution in ultrathin semimetallic NiTe2 films

Abstract Nickel ditelluride (NiTe 2 ), a recently discovered Type-II Dirac semimetal with topological fermions near the Fermi energy, is expected to exhibit strong thickness-mediated electronic tunability and intrinsic two-gap superconductivity in single-layer limit. Realizing such intriguing phenomena requires fabrication of ultrathin NiTe films an understanding underlying physics that still under debate. By conducting experimental band mappings prepared molecular beam epitaxy, we reveal spectroscopic evidence for dimensionality crossover single-crystalline as function film thickness. As thickness increases from one five layers, gap conical surface states closes. Comparisons first-principles results also highlight difficulties fabricating atomically smooth films. Our not only provide further impetus studying emergent but underscore limitations device applications.