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RESEARCH PRODUCT

Density of Phonon States in Superconducting FeSe as a Function of Temperature and Pressure

Vadim KsenofontovTyrel M. McqueenTeuta GasiRobert J. CavaClaudia FelserS. A. MedvedevS. A. MedvedevGerhard WortmannA. I. Chumakov

subject

PhysicsSuperconductivityPhase transitionMössbauer effectCondensed matter physicsPhononCondensed Matter - SuperconductivityResolution (electron density)FOS: Physical sciencesInelastic scatteringCondensed Matter PhysicsCoupling (probability)Electronic Optical and Magnetic MaterialsSuperconductivity (cond-mat.supr-con)Condensed Matter::SuperconductivityCondensed Matter::Strongly Correlated ElectronsAtomic physicsSpin-½

description

The temperature and pressure dependence of the partial density of phonon states (phonon-DOS) of iron atoms in superconducting ${\text{Fe}}_{1.01}\text{Se}$ was studied by $^{57}\text{F}\text{e}$ nuclear inelastic scattering. The high-energy resolution allows for a detailed observation of spectral properties. A sharpening of the optical phonon modes and shift of all spectral features toward higher energies by $\ensuremath{\sim}4\mathrm{%}$ with decreasing temperature from 296 to 10 K was found. However, no detectable change at the tetragonal--orthorhombic phase transition around 100 K was observed. Application of a pressure of 6.7 GPa, connected with an increase in the superconducting temperature from 8 to 34 K, results in an increase in the optical phonon mode energies at 296 K by $\ensuremath{\sim}12\mathrm{%}$, and an even more pronounced increase for the lowest-lying transversal acoustic mode. Despite these strong pressure-induced modifications of the phonon-DOS we conclude that the pronounced increase in ${T}_{\text{c}}$ in ${\text{Fe}}_{1.01}\text{Se}$ with pressure cannot be described in the framework of classical electron-phonon coupling. This result suggests the importance of spin fluctuations to the observed superconductivity.

10.1103/physrevb.81.184510http://arxiv.org/abs/1004.2007