Coexistence of Polaronic States and Superconductivity in Iron-Pnictide Compound Ba_2Ti_2Fe_2As_4O

The electronic structure of iron-pnictide compound superconductor Ba_2Ti_2Fe_2As_4O, which has metallic intermediate Ti_2O layers, is studied using angle-resolved photoemission spectroscopy. The Ti-related bands show a‘peak-dip-hump' line shape with two branches of dispersion associated with the polaronic states at temperatures below around 120 K. This change in the spectra occurs along with the resistivity anomaly that was not clearly understood in a previous study. Moreover, an energy gap induced by the superconducting proximity effect opens in the polaronic bands at temperatures below T_c(~21 K). Our study provides the spectroscopic evidence that superconductivity coexists with polarons in the same bands near the Fermi level, which provides a suitable platform to study interactions between charge, lattice and spin freedoms in a correlated system.     

具有给定阶和最大度的单圈图的最大匹配能量

图的匹配能量由UTMAN等于2012年提出,定义为图的匹配多项式的根的绝对值的和. 如果一个连通图的边数与点数相等, 或有唯一的一个圈,则称为单圈图.刻画了在具有给定阶与最大度的所有单圈图中达到最大匹配能量的图.     

Hybridization Effects Revealed by Angle-Resolved Photoemission Spectroscopy in Heavy-Fermion Ce_2IrIn_8

We utilize high-resolution resonant angle-resolved photoemission spectroscopy(ARPES)to study the band structure and hybridization effect of the heavy-fermion compound Ce_2 IrIn_8.We observe a nearly flat band at the binding energy of 7 meV below the coherent temperature T_(coh)～40 K,which characterizes the electrical resistance maximum and indicates the onset temperature of hybridization.However,the Fermi vector and the Fermi surface volume have little change around T_(coh),which challenges the widely believed evolution from a hightemperature small Fermi surface to a low-temperature large Fermi surface.Our experimental results of the band structure fit well with the density functional theory plus dynamic mean-field theory calculations.     

倒距离矩阵的谱半径(英文)

本文刻画了在分别具有给定点连通度、边连通度、色数和独立数的n阶图中具有最大倒距离矩阵谱半径的图.