Strain-induced Aharonov-Bohm effect at nanoscale and ground state of a carbon nanotube with zigzag edges

Magnetic flux piercing a carbon nanotube induce periodic gap oscillations which represent the Aharonov-Bohm effect at nanoscale. Here we point out, by analyzing numerically the anisotropic Hubbard model on a honeycomb lattice, that similar oscillations should be observable when uniaxial strain is applied to a nanotube. In both cases, a vector potential (magnetic- or strain-induced) may affect the measurable quantities at zero field. The analysis, carried out within the Gutzwiller Approximation, shows that for small semiconducting nanotube with zigzag edges and realistic value of the Hubbard repulsion (U/t$_{0}$ = 1.6, with t$_{0}$ = 2.5 eV being the equilibrium hopping integral) energy gap can be reduced by a factor of more than 100 due to the strain

On the strongly correlated quantum matter paradigm : magnetism–superconductivity redux

The principal dilemma of real-space pairing versus pairing of electron–lattice (or other) origin can, in our view, be addressed properly for strongly correlated systems by explaining an overall phase diagram involving different magnetic and superconducting phases within a single consistent framework. In this comment, particular emphasis is put on the connection/coexistence with antiferromagnetism, as well as on the existence of the upper critical concentration for the disappearance of superconductivity in high-temperature superconductors. The analysis provides clear evidence for the kinetic exchange as being a natural origin of both phenomena, in conjunction with the strongly correlated motion (hopping) of the carriers. A subtle difference between the exchange- and the paramagnon-induced pairing is also noted. An analogical scenario is advocated briefly for heavy fermion systems. Some further tests are proposed in order to provide a convincing proof of the magnetic origin, combined with the strongly correlated nature of carriers, of this unconventional superconductivity and its universality in strongly correlated systems, solid-state or otherwise. The role of strong correlations among the fermions composing Cooper pairs is emphasized

Mott Transition in the Hubbard Model on Anisotropic Honeycomb Lattice with Implications for Strained Graphene: Gutzwiller Variational Study

The modification of interatomic distances due to high pressure leads to exotic phenomena, including metallicity, superconductivity and magnetism, observed in materials not showing such properties in normal conditions. In two-dimensional crystals, such as graphene, atomic bond lengths can be modified by more than 10 percent by applying in-plane strain, i.e., without generating high pressure in the bulk. In this work, we study the strain-induced Mott transition on a honeycomb lattice by using computationally inexpensive techniques, including the Gutzwiller Wave Function (GWF) and different variants of Gutzwiller Approximation (GA), obtaining the lower and upper bounds for the critical Hubbard repulsion (U) of electrons. For uniaxial strain in the armchair direction, the band gap is absent, and electron correlations play a dominant role. A significant reduction in the critical Hubbard U is predicted. Model considerations are mapped onto the tight-binding Hamiltonian for monolayer graphene by the auxiliary Su–Schrieffer–Heeger model for acoustic phonons, assuming zero stress in the direction perpendicular to the strain applied. Our results suggest that graphene, although staying in the semimetallic phase even for extremely high uniaxial strains, may show measurable signatures of electron correlations, such as the band narrowing and the reduction in double occupancies