Pairing mechanism of heavily electron doped FeSe systems: dynamical tuning of the pairing cutoff energy. (29th November 2016)

• Record Type: Journal Article
• Authors: Bang, Yunkyu
• Is Part Of: New journal of physics. Volume 18:Number 11(2016:Nov.)
• Publication Date: 2016-11-29
• Subjects: Iron-based superconductors -- heavily electron doped fese systems -- high-tc superconductivity -- renormalization of cutoff energy; 74.20.-z -- 74.20.Rp -- 74.70.Xa; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/18/11/113054
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: We studied the pairing mechanism of the heavily electron doped FeSe (HEDIS) systems, which commonly have one incipient hole band—a band top below the Fermi level by a finite energy distance ε b —at Γ point and ordinary electron bands at M points in Brillouin zone (BZ). We found that the system allows two degenerate superconducting solutions with the exactly same T c in clean limit: the incipient s he ± -gap ( Δ h − ≠ 0, Δ e + ≠ 0 ) and s ee ++ -gap (Δ h = 0, Δ e + ≠ 0 ) solutions with different pairing cutoffs, Λ sf (spin fluctuation energy) and ε b, respectively. The s ee ++ -gap solution, in which the system dynamically renormalizes the original pairing cutoff Λ sf to Λphys = ε b (<Λ sf ), therefore actively eliminates the incipient hole band from forming Cooper pairs, but without loss of T c, becomes immune to the impurity pair-breaking. As a result, the HEDIS systems, by dynamically tuning the pairing cutoff and therefore selecting the s ee ++ -pairing state, can always achieve the maximum T c —the T c of the degenerate s he ± solution in the ideal clean limit—latent in the original pairing interactions, even in the dirty limit.