Synopsis: Back to basics

Minimal two-band model of the superconducting iron oxypnictides

S. Raghu, Xiao-Liang Qi, Chao-Xing Liu, D. J. Scalapino, and Shou-Cheng Zhang

Published June 11, 2008

The condensed matter community’s current excitement over a new class of iron-based superconductors closely resembles the early days in the discovery of high-temperature superconductivity in copper-based (cuprate) oxides. New compounds are being discovered nearly every month, with the highest reported transition temperature approaching 55 K. Similar to the copper-oxide layers in the high-Tc cuprates, the new superconductors consist of conducting iron-arsenide layers that are separated by insulating rare-earth-oxide layers. First-principles calculations have shown that superconductivity is associated with the iron-arsenide layers, but these studies are based on complex models that can only be solved with computational methods and a more intuitive model is required. In a Rapid Communication appearing in the June 11th issue of Physical Review B, Srinivas Raghu and Shou-cheng Zhang of Stanford, Douglas Scalapino of the University of California, Santa Barbara, and collaborators have distilled the current knowledge on this complicated system into a simple model.

They construct an effective Hamiltonian that correctly reproduces the structure of the electronic Fermi surface in the normal state, which is a necessary first step for understanding the superconducting state. They also find magnetic behavior associated with the iron-arsenide layer that is thought to be connected to superconductivity in these materials.

The work may be viewed as the iron-arsenide analog of the classic paper by Zhang and Rice [1], which introduced an effective Hamiltonian for the cuprates. Such simple models that capture the low-energy physics are indispensable starting points for theorists as they attempt to reproduce the properties of these complex materials. - Alexios Klironomos

[1] Zhang, F-C. and Rice, T. M. Phys. Rev. B 37, 3759(R) (1988)

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