Fermi Liquid Breakdown and Evidence for Superconductivity in YFe₂Ge₂

Abstract

In the d-electron system YFe 2 Ge 2 , an unusually high and temperature dependent Sommerfeld ratio of the specific heat capacity C/T ∼ 100 mJ/(molK 2 ) and an anomalous power law temperature dependence of the electrical resistivity ρ ρ 0 + AT 3/2 signal Fermi liquid breakdown, probably connected to a close-by quantum critical point.Full resistive transitions, accompanied by DC diamagnetic screening fractions of up to 80% suggest that pure samples of YFe 2 Ge 2 superconduct below 1.8 K.

Crystal growth and annealing study of fragile, non-bulk superconductivity in YFe2Ge2

“…It has weak temperature dependence which is slowly increasing upon cooling, and is consistent with the data taken on a polycrystalline sample. 15 The data of the C p (T ) at higher temperatures show excellent agreement with the results presented in Ref. 8 (data not shown).…”

“…• C. The electrical resistivity drops to zero, and the sample expels weak magnetic fields at low temperatures (T < 1.8 K), 15 which is consistent with the presence of a superconducting phase in this sample. 15 If this superconductivity is found to be bulk and intrinsic to YFe 2 Ge 2 , then this stoichiometric compound could possibly be added into the class of Fe-based superconductors as a new member with its electron count being equivalent to the nodal superconductor KFe 2 As 2 ,…”

“…15,16 Based on results of first-principle calculations, the superconductivity observed in this compound is compatible with either the sign-changing multi s-wave, so-called s ± -wave, 17 or spin fluctuation mediated spin triplet superconductivity, 16 some of which might have the superconducting transition temperature depending sensitively on disorder. However, there has been no systematic work on the relation between the superconducting transition temperature and the impurity scattering in YFe 2 Ge 2 .…”

“…15 If this superconductivity is found to be bulk and intrinsic to YFe 2 Ge 2 , then this stoichiometric compound could possibly be added into the class of Fe-based superconductors as a new member with its electron count being equivalent to the nodal superconductor KFe 2 As 2 ,…”

“…Finding superconductivity in YFe 2 Ge 2 is intriguing particularly because the compound has high density of states at the Fermi level as inferred from the large Sommerfeld coefficient 8,15 and the electrical resistivity • C and 800…”