paper

Collective excitations of dynamic Fermi surface deformations in BaFe $_{2}$ (As $_{0.5}$ P $_{0.5}$ ) $_{2}$

arXiv:1607.06575

Abstract

We use electronic Raman scattering to study the low-energy excitations in BaFe $_{2}$ (As $_{0.5}$ P $_{0.5}$ ) $_{2}$ ( $T_{c} \approx 16$ K) samples. In addition to a superconducting pair breaking peak (2 $I^ = 6.7$ meV) in the A $_{1 g}$ channel with a linear tail towards zero energy, suggesting a nodal gap structure, we detect spectral features associated to Pomeranchuk oscillations in the A $_{1 g}$ , B $_{1 g}$ and B $_{2 g}$ channels. We argue that the small Fermi energy of the system is an essential condition for these Pomeranchuk oscillations to be underdamped. The Pomeranchuk oscillations have the same frequencies in the B $_{1 g}$ and B $_{2 g}$ channels, which we explain by the mixing of these symmetries resulting from the removal of the $I ¨ _{v}$ and $I ¨ _{v}$ symmetry planes due to a large As/P disorder. Interestingly, we show that the temperature at which the peaks corresponding to the Pomeranchuk oscillations get underdamped is consistent with the non-Fermi liquid to Femi liquid crossover determined by transport, suggesting that the Pomeranchuk instability plays an important role in the low-energy physics of the Fe-based superconductors.

5 pages, 4 figures

Collective excitations of dynamic Fermi surface deformations in BaFe2​(As0.5​P0.5​)2​

Abstract

Collective excitations of dynamic Fermi surface deformations in BaFe $_{2}$ (As $_{0.5}$ P $_{0.5}$ ) $_{2}$