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

Condensed Matter. 2022. Vol. 7. No. 3. Article 50.

Sboychakov A., Kliment I. Kugel, Bianconi A.

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 = eb (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
e = 9/h in the range 36 > h > 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.

Keywords: Van Hove singularities, superstructures, cuprate bilayers, electron density of states, сверхструктуры, двухслойные купраты, электронная плотность состояний, особенности ван Хова