Multiple Electronic Components and Lifshitz Transitions by Oxygen Wires Formation in Layered Cuprates and Nickelates

Thomas Jarlborg,Antonio Bianconi

doi:10.3390/condmat4010015

Abstract

There is growing compelling experimental evidence that a quantum complex matter scenario made of multiple electronic components and competing quantum phases is needed to grab the key physics of high critical temperature ( T c ) superconductivity in layered cuprates. While it is known that defect self-organization controls T c , the mechanism remains an open issue. Here we focus on the theoretical prediction of the multiband electronic structure and the formation of broken Fermi surfaces generated by the self-organization of oxygen interstitials O i atomic wires in the spacer layers in HgBa 2 CuO 4 ± δ , La 2 CuO 4 ± δ and La 2 NiO 4 ± δ , by means of self-consistent Linear Muffin-Tin Orbital (LMTO) calculations. The electronic structure of a first phase of ordered O i atomic wires and of a second glassy phase made of disordered O i impurities have been studied through supercell calculations. We show the common features of the influence of O i wires in the electronic structure in three types of materials. The ordering of O i into wires leads to a separation of the electronic states between the O i ensemble and the rest of the bulk. The wire formation first produces quantum confined localized states near the wire, which coexist with, Second, delocalized states in the Fermi surface (FS) of doped cuprates. A new scenario emerges for high T c superconductivity, where Kitaev wires with Majorana bound states are proximity-coupled to a 2D d-wave superconductor.

Highlights

The mechanism behind the emergence of high Tc superconductivity remains the object of high scientific interest [1,2,3]
EF is on a narrow peak in both cells with O impurities, which makes the density of states (DOS) higher, about 3 and 4−1 per elementary cell for the striped and disordered case, respectively
Ordering of the mobile dopants oxygen interstitial (Oi) into wired puddles contributes to a potential modulation with the formation of quasi-1D bands due to dopants at high doping

Summary

Introduction

The mechanism behind the emergence of high Tc superconductivity remains the object of high scientific interest [1,2,3]. All high Tc superconductors show a superconducting dome, centered at the maximum TCmax tuning the chemical potential by doping or pressure. The high Tc superconductivity violates the standard approximations of BCS theory [4]: (1) the dirty limit. Approximation reducing the multiple bands electronic structure to a single effective Fermi surface (FS); and (2) the Migdal approximation where chemical potential is far away from the band edges. The popular theoretical paradigms for cuprates assuming a single electronic component or a large Fermi surface have been abandoned. Many recent experiments show compelling evidence for a quantum complex matter (QCM) phase, called superstripes scenario [5,6] characterized by nanoscale spatial phase separation, coexisting multiple electronic components, multiple Fermi surfaces and proximity to Lifshitz transitions [7]. Since 1987 it was shown that hole doping cuprates form additional 3d9L states in the correlation gap of the undoped phase [8,9]

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Conclusion