Moiré-like Superlattice Generated van Hove Singularities in a Strained CuO2 Double Layer

Abstract

While it is known that the double-layer Bi2Sr2CaCu2O8+y (BSCCO) cuprate superconductor exhibits a one-dimensional (1D) incommensurate superlattice (IS), the effect of IS on the electronic structure remains elusive. Following the recent shift of interest from an underdoped phase to optimum and overdoped phases in BSCCO by increasing the hole doping x, controlled by the oxygen interstitials concentration y, here we focus on the multiple splitting of the density of states (DOS) peaks and emergence of higher order van Hove singularities (VHS) due to the 1D incommensurate superlattice. It is known that the 1D incommensurate wave vector q=ϵb (where b is the reciprocal lattice vector of the orthorhombic lattice) is controlled by the misfit strain between different atomic layers in the range 0.209–0.215 in BSCCO and in the range 0.209–0.25 in Bi2Sr2Ca1−xYxCu2O8+y (BSCYCO). This work reports the theoretical calculation of a complex pattern of VHS due to the 1D incommensurate superlattice with large 1D quasi-commensurate supercells with the wave vector ϵ=9/η in the range 36>η>43. The similarity of the complex VHS splitting and appearing of higher order VHS in a mismatched CuO2 bilayer with VHS due to the moiré lattice in strained twisted bilayer graphene is discussed. This makes a mismatched CuO2 bilayer quite promising for constructing quantum devices with tuned physical characteristics.

Superlattice Delineated Fermi Surface Nesting and Electron-Phonon Coupling in CaC6

“…In addition, superlattices have been used to model striped structures, experimentally observed in superconductors at both nano [15] and atomic [16] scales. The effects of modulated strain on superconducting materials, both from the intrinsic crystal structure of the complex metal oxide [3] or artificially created to mimic those strain modulations [17], are also linked to superlattice observations and models.…”