Low-temperature lattice anomaly in LaFeAsO0.93F0.07 probed by x-ray absorption spectroscopy: Evidence for strong electron-lattice interaction

TL;DR

This study reveals a low-temperature lattice anomaly in LaFeAsO0.93F0.07 superconductors, showing strong electron-lattice interactions that are closely linked to the superconducting transition, as evidenced by x-ray absorption spectroscopy.

Contribution

It provides direct experimental evidence of lattice fluctuations associated with superconductivity in oxypnictides, highlighting the role of electron-lattice interaction in these materials.

Findings

Anomalous upturn of Fe-As bond displacement below ~70 K

Lattice fluctuation sharply decreases at superconducting transition

Strong electron-lattice interaction influences superconductivity

Abstract

The local lattice structure in newly discovered LaFeAsO1-xFx superconductors is studied by extended x-ray absorption fine structure measurements. An anomalous upturn of the mean-square relative displacement of the Fe-As bond is detected below ~70 K as electron carriers are introduced,reflecting the occurrence of Fe-As bond local lattice fluctuation. Similar to that in cuprates, this lattice fluctuation exhibits an abrupt depression at the onset superconducting transition temperature. The results indicate that strong electron-lattice interaction is involved in the superconducting transition in oxypcnictide superconductors, putting a strict limitation on possible theoretical models.