Characterizing the insulator adjacent to the superconductor in Bi$_2$Sr$_{2-x}$La$_{x}$CuO$_{6+δ}$ ($x=0.3$)

用ARPES研究三层铜氧化物Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+δ}$中相邻CuO$_2$层间Bogoliubov准粒子的杂化

Hybridization of Bogoliubov-quasiparticles between adjacent CuO$_2$ layers in the triple-layer cuprate Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+δ}$ studied by ARPES

本研究用ARPES探究三层铜氧化物超导体中相邻CuO₂层间Bogoliubov准粒子的杂化，揭示其反交叉能隙起源、d波能隙演化特征与杂化的动量依赖性，并讨论了超导转变温度提升的可能机制。

Origin of the unusual strong suppression of low frequency antiferromagnetic fluctuations in underdoped HgBa$_2$CuO$_{4+δ}$

Generally strong charge and magnetic inhomogeneities are observed in NQR/NMR experiments on underdoped cuprates. It is not the case for the underdoped HgBa$_2$CuO$_{4+δ}$, the most symmetric and highest T$_c$ single layer cuprate, whose magnetic inhomogeneity is strongly suppressed. Also neutron scattering experiments reveal a unique pair of weakly dispersive magnetic modes in this material. We propose that these special properties stem from the symmetric positioning of the O-dopants between adjacent CuO$_2$ layers that lead to a strong superexchange interaction between a pair of hole spins. I…

Effect of disorder outside the CuO$_{2}$ planes on $T_{c}$ of copper oxide superconductors

The effect of disorder on the superconducting transition temperature $T_{c}$ of cuprate superconductors is examined. Disorder is introduced into the cation sites in the plane adjacent to the CuO$_{2}$ planes of two single-layer systems, Bi$_{2.0}$Sr$_{1.6}$Ln$_{0.4}$CuO$_{6+δ}$ and La$_{1.85-y}$Nd$_{y}$Sr$_{0.15}$CuO$_{4}$. Disorder is controlled by changing rare earth (Ln) ions with different ionic radius in the former, and by varying the Nd content in the latter with the doped carrier density kept constant. We show that this type of disorder works as weak scatterers in contrast to the in-pla…

Effects of antiferromagnetic planes on the superconducting properties of multilayered high-Tc cuprates

We propose a mechanism for high critical temperature (T_c) in the coexistent phase of superconducting- (SC) and antiferromagnetic (AF) CuO_2 planes in multilayered cuprates. The Josephson coupling between the SC planes separated by an AF insulator (Mott insulator) is calculated perturbatively up to the fourth order in terms of the hopping integral between adjacent CuO_2 planes. It is shown that the AF exchange splitting in the AF plane suppresses the so-called pi-Josephson coupling, and the long-ranged 0-Josephson coupling leads to coexistence with a rather high value of T_c.

A resolution to doping asymmetry puzzle in high Tc cuprates

We present a microscopic model for `electron doped' $Nd_{2-x}Ce_xCuO_4$ family and offer a resolution to a long standing doping asymmetry puzzle. Here, i) Ce atoms do not dope free electrons, instead a Ce atom effectively quenches a $Cu^{2+}$ spin moment at an adjacent site, at an energy scale > superexchange J of $CuO_2$ plane and `site dilutes' the Mott insulator. ii) Effective chemical pressure, caused by increased Ce substitution, induces a {\em first order Mott insulator to superconductor transition} in the $CuO_2$ plane. We predict, i) {\em equal number of +e and -e carriers} in metallic…

Coexistence of metallicity and superconductivity in adjacent bilayers of a high-Tc superconductor

Experimental studies of the electronic structure remain the basic means for understanding the nature of high-temperature superconductivity (HTSC) and testing relevant theoretical models. Appreciable contributions to establish the overall picture in HTSC have recently been made by investigations on the charge dynamics in BSCCO (ref. 1) and the spin dynamics in YBCO, using Angle Resolved Photoemission Spectroscopy (ARPES) and Inelastic Neutron Scattering (INS), respectively. Concentration of each of these techniques on a "suitable" compound turns out to be a barrier on the way to a crucial quant…