Observation of multilayer quantum Hall effect in the charge density wave material CaCu_{4}As_{2}

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 CaCu_{4}As_{2}, which crystallizes in a rhombohedral lattice. Temperature-dependent single-crystal x-ray diffraction in conjunction with thermodynamic and transport measurements reveal that CaCu_{4}As_{2} undergoes a structural or CDW transition below 51 K. For I∥[12[over ¯]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. CaCu_{4}As_{2} thus provides a new platform to understand the coexistence of both the CDW and quantum Hall effect in materials.