Modulation of charge-density waves by superlattice structures

Abstract

We discuss the interplay between electronic correlations and an underlying superlattice structure in determining the period of charge density waves ͑CDW's͒, by considering a one-dimensional Hubbard model with a repeated ͑nonrandom͒ pattern of repulsive ͑U Ͼ 0͒ and free ͑U =0͒ sites. Density matrix renormalization group diagonalization of finite systems ͑up to 120 sites͒ is used to calculate the charge-density correlation function and structure factor in the ground state. The modulation period can still be predicted through effective Fermi wave vectors k F * and densities, and we have found that it is much more sensitive to electron ͑or hole͒ doping, both because of the narrow range of densities needed to go from q * =0 to , but also due to sharp 2k F * −4k F * transitions; these features render CDW's more versatile for actual applications in heterostructures than in homogeneous systems.

Structure-dependent metal–insulator transition in one-dimensional Hubbard superlattice

“…[19] For considerable insight into the nonrandom inhomogeneous systems such as magnetic multilayer and superlattice, [20][21][22][23] a 1D superlattice model with periodic arrangement of repulsive and free sites, but with constant orbital energy, has been widely studied for many different unit cell configurations and electron fillings. [24][25][26][27][28][29][30] The Mott-Hubbard insulator sets in at filling density ρ I for these superlattice structures, [25] not at halffilling as in the Hubbard model. The period of SDW and the profile of local moment have rich properties.…”

Exceptional points in the one-dimensional Hubbard model

“…In the simplest case, we have U A = 0 and U B = 0. Such a model was previously investigated for its various properties that are different from the homogeneous chain: transfer of the magnetic momentum to the free sites 39 , the appearance of a giant magnetoresistance effect 40,41 , a Mott insulator transition that may occur at fillings other than half filling 42 , and the formation of a modulated and potentially incommensurate charge-density wave [43][44][45] . However, we note that in contrast to previous studies, our model includes alternating on-site energies instead of a homogeneous chemical potential.…”

Incommensurate charge correlation and phase diagram of the one-dimensional superlattice Hubbard model at half-filling

“…The superlattice model corresponding to U B = = 0 in equation ( 1) has even been proposed for magnetic metallic multilayers [15]. The magnetism, the MIT and the chargedensity wave have been studied for electronic density away from half-filling [16][17][18]. However, no phase transition was observed at half-filling since the orbital energy = 0 was chosen in these works.…”