Observation of multilayer quantum Hall effect in the charge density wave material CaCu4As2

Abstract

Low-dimensional layered materials manifest an inherent tendency towards the formation of symmetry reduced charge density wave (CDW) states with exotic properties. Here, we elucidate the anisotropic transport properties of CaCu4As2, which crystallizes in a rhombohedral lattice. Temperature-dependent single-crystal x-ray diffraction in conjunction with thermodynamic and transport measurements reveal that CaCu4As2 undergoes a structural or CDW transition below 51 K. For Iâ [12¯10], angular-dependent Shubnikov-de Haas oscillations reveal a two-dimensional nature of the charge carriers contributing to the bulk transport in accord with our calculated Fermi surface. In the inverse Hall resistance versus 1/B plot, quantized Hall plateaus are observed. CaCu4As2 thus provides a new platform to understand the coexistence of both the CDW and quantum Hall effect in materials.