Feshbach Shape Resonances in Multiband High Tc Superconductors

Abstract

Abstract:We describe particular nanoarchitectures (superlattices of superconducting wires and layers) where a mechanism to evade temperature decoherence effects in a quantum condensate is switched on by tuning the charge density. The superlattice structure determines the subbands and the corresponding Bloch wavefunctions of charge carriers at the Fermi level with different parity and different spatial locations. The disparity and negligible overlap between electron wave-functions in different subbands suppress the single electron interband impurity scattering rate and allow the multiband superconductivity in the clean limit. The quantum trick that bestows to the system the property to resist to the decoherence attacks of high temperature is the Feshbach shape resonance in the interband off-diagonal exchange-like pairing term i.e., in the quantum configuration interaction between pairing channels in different subbands. It occurs by tuning the chemical potential at a particular point near a Van Hove singularity (vHs) in the electronic energy spectrum, or a Lifshitz electronic topological transition (ETT), associated with the change of the dimensionality of the Fermi surface topology of one of the subbands.

Far from Equilibrium Percolation, Stochastic and Shape Resonances in the Physics of Life

“…The clearest configuration interaction between many body functions is the case of shape resonance in the superconducting gaps [ 84 – 87 ] arising from the mixing between a Bardeen-Cooper-Schriffer (BCS) condensate in a first band i with a Bose-like condensate in a different band j with a finite width near a Lifshitz transition [ 87 ]. The interference term, called the “interband pairing” transfers a pair of spin up and spin down particles from the first i to the second j condensate and vice-versa.…”

Shape Resonance at a Lifshitz Transition for High Temperature Superconductivity in Multiband Superconductors

“…i) boron honeycomb layers separated by Al, Mg or Sc layers, (called diborides) [33][34][35][36][37][38] ii) honeycomb graphene layers intercalated by different spacer layers (called intercalated graphite) [39] iii) iron fcc layers intercalated by many different types of spacers (called pnictides or iron-based superconductors) [40][41][42][43][44][45][46][47], iv) superlattices of carbon nanotubes [48] In fact all these systems show similar features [49][50][51][52] being multilayers near a Lifshitz transition. In this 2.5 electronic phase transition [53][54][55][56][57][58][59][60] the system is in the verge of a first order phase transition, with the possible appearance of a tricritical point.…”

Nonadiabatic coupling of the dynamical structure to the superconductivity in YSr 2 Cu 2.75 Mo 0.25 O 7.54 and Sr 2 CuO 3.3

“…Experimentally, however, anomalous isotope effects ( 5 ), resonant ultrasound ( 6 ), angle-resolved photoemission spectroscopy ( 7 – 9 ), femtosecond optical pump terahertz ( 10 )/megaelectron-volt transmission electron microscopy probe ( 11 ), infrared pump ( 12 ), and so on have demonstrated that specific phonons not only couple to the superconductivity but correlate directly with the gap energy and may even transiently induce it well above the superconducting critical temperature, T c . Cuprates also exhibit a plethora of superstructures indicative of strong electron–lattice coupling, stripes that have been proposed to stabilize the superconductivity ( 13 ), and charge-density waves ( 14 , 15 ) and the pseudogap (PG) ( 16 ) that compete with it. Another possibility is mechanisms that boost T c from a low value expected within a conventional Bardeen-Cooper-Schrieffer (BCS) scheme.…”