2013/06/30 by Maria Grazia Marciani, M. Marciani, L. Fanfarillo +3 · 77 citations
Business, Management and Accounting · Materials Science · Physics and Astronomy · #Antibonding molecular orbital #Atomic orbital #Condensed matter physics #Corporate Taxation and Avoidance #Electron #Electron pair #Iron-based superconductors research #Pairing #Phase (matter) #Physics #Quantum mechanics #Spin (aerodynamics) #Superconductivity #Superconductivity in MgB2 and Alloys #Symmetry (geometry) #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.88.214508
published in Physical Review B 88(21) (American Physical Society) · New references added, final version as published
openalex publication_date 2013/12/10 · arxiv created 2014/01/13 · arxiv updated 2014/01/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Since their discovery, it has been suggested that pairing in pnictides can be mediated by spin fluctuations between hole and electron bands. In this view, multiband superconductivity would substantially differ from other systems like MgB2, where pairing is predominantly intraband. Indeed, interband-dominated pairing leads to the coexistence of bonding and antibonding superconducting channels. Here, we show that this has profound consequences on the nature of the low-energy superconducting collective modes. In particular, the so-called Leggett mode for phase fluctuations is absent in the usual two-band description of pnictides. On the other hand, when also the repulsion between the hole bands is taken into account, a more general three-band description should be used, and a Leggett mode is then allowed. Such a model, which has been proposed for strongly hole-doped 122 compounds, can also admit a low-temperature s+is phase that breaks the time-reversal symmetry. We show that the (quantum and thermal) transition from the ordinary superconductor to the s+is state is accompanied by the vanishing of the mass of Leggett-like phase fluctuations, regardless the specific values of the interaction parameters. This general result can be obtained by means of a generalized construction of the effective action for the collective degrees of freedom that allows us also to deal with the nontrivial case of dominant interband pairing.