超导体Sr2VO3FeAs中钒的弱磁性和莫特态
Weak magnetism and the Mott-state of vanadium in superconducting Sr2VO3FeAs
摘要：
我们报告的中子散射数据和密度泛函理论计算的化学计量比的铁砷化物超导体Sr 2 VO 3FeAs。Rietveld改进的中子粉末图案证实了没有氧缺陷的理想成分。极化中子实验证实了Sr 2 VO 3FeAs在~ 45 K时的弱磁有序性，其传播矢量q =（1/8，1/8，0）。~ 0.1 μ B的有序矩太小，不能通过磁交换分裂从费米能级去除V-3d带，并且比最近LDA+U研究预测的要小得多。通过GGA+EECE泛函的DFT计算，我们恢复了典型的准嵌套费米面，即使没有磁矩。由此我们认为V-原子处于Mott态，其中电子关联由在位库仑排斥控制，这使V-3d态远离费米能。我们的研究结果是一致的光电子能谱数据，并清楚地表明，Sr 2 VO 3FeAs是一个典型的铁砷化物超导体与准嵌套的空穴和电子类费米面片，并构成没有新的范例。我们认为，通过V3+/V4+混合价的本征电子掺杂是负责的SDW有序的情况下。
英文摘要：
We report neutron scattering data and DFT calculations of the stoichiometric iron-arsenide superconductor Sr2VO3FeAs. Rietveld refinements of neutron powder patterns confirm the ideal composition without oxygen deficiencies. Experiments with polarized neutrons prove weak magnetic ordering in the V-sublattice of Sr2VO3FeAs at ~ 45 K with a probable propagation vector q = (1/8,1/8,0). The ordered moment of ~ 0.1 muB is too small to remove the V-3d bands from the Fermi level by magnetic exchange splitting, and much smaller than predicted from a recent LDA+U study. By using DFT calculations with a GGA+EECE functional we recover the typical quasi-nested Fermi-surface even without magnetic moment. From this we suggest that the V-atoms are in a Mott-state where the electronic correlations are dominated by on-site Coulomb-repulsion which shifts the V-3d states away from the Fermi energy. Our results are consistent with photoemission data and clearly reveal that Sr2VO3FeAs is a typical iron-arsenide superconductor with quasi-nested hole- and electron-like Fermi surface sheets, and constitutes no new paradigm. We suggest that intrinsic electron-doping through V3+/V4+ mixed valence is responsible for the absence of SDW ordering.
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