Shape resonances in multi-condensate granular superconductors formed by networks of nanoscale-striped puddles

Antonio Bianconi

doi:10.1088/1742-6596/449/1/012002

Antonio Bianconi

Open Access

https://doi.org/10.1088/1742-6596/449/1/012002

Copy DOI

Abstract

A characteristic feature of a superconductor made of multiple condensates is the possibility of the shape resonances in superconducting gaps. Shape resonances belong to class of Fano resonances in configuration interaction between open and closed scattering channels. The Shape resonances arise because of the exchange interaction, a Josephson-like term, for transfer of pairs between different condensates in different Fermi surface spots in the special cases where at least one Fermi surface is near a 2.5 Lifshitz topological transition. We show that tuning the shape resonances show first, the gap suppression (like a Fano anti-resonance) driven by configuration interaction between a BCS condensate and a BEC-like condensate, and second, the gap amplification (like a Fano resonance) driven by configuration interaction between BCS condensates in large and small Fermi surfaces. Shape resonances usually occur in granular nanoscale complex matter (called superstripes) because of the lattice instability near a 2.5 Lifshitz transition in presence of interactions. Using a new imaging method, scanning nano-X-ray diffraction, we have shown the generic formation in high temperature superconductors of a granular superconducting networks made of striped puddles formed by ordered oxygen interstitials or ordered local lattice distortions (like static short range charge density waves). In the superconducting puddles the chemical potential is tuned to a shape resonance in superconducting gaps and the maximum Tc occurs where the puddles form scale free superconducting networks.

Highlights

Understanding the mechanism that allows a quantum condensate to resist decoherence attacks of temperature is a major fundamental problem of condensed matter
The high Tc dome appears near a 2.5 Lifshitz transition near a band edge
At list one of the borders of the high Tc dome is determined by the Fano anti-resonance of the shape resonance in the superconducting gaps where Tc drops toward zero at the 2.5 Lifshitz transition for the appearing of a new Fermi surface

Summary

Introduction

Understanding the mechanism that allows a quantum condensate to resist decoherence attacks of temperature is a major fundamental problem of condensed matter. A clear practical realization of this scenario is MgB2, a material known since 1953, where superconductivity was never measured for 46 years since no superconductivity was predicted by standard theories based on the effective single band “dirty limit” dogma but on the contrary high temperature superconductivity was predicted by the multiband theory if the chemical potential is driven near a band edge i.e., below the top of the boron 2px,y sigma band where it should form a multi-gap superconductor in the “clean limit” because of single electron hopping between π and σ bands are forbidden by symmetry [16,17,18,19].

Results

Conclusion