Abstract
In the recent search for unconventional- and topological superconductivity, noncentrosymmetric superconductors (NCSCs) rank among the most promising candidate materials. Surprisingly, some of them—especially those containing rhenium—seem to exhibit also time-reversal symmetry (TRS) breaking in their superconducting state, while TRS is preserved in many other isostructural NCSCs. To date, a satisfactory explanation for such discrepant behavior, albeit crucial for understanding the unconventional superconductivity of these materials, is still missing. Here we review the most recent developments regarding the Re-based class, where the muon-spin relaxation (μSR) technique plays a key role due to its high sensitivity to the weak internal fields associated with the TRS breaking phenomenon. We discuss different cases of Re-containing superconductors, comprising both centrosymmetric- and noncentrosymmetric crystal structures, ranging from pure rhenium, to ReT (T = 3d-5d early transition metals), to the dilute-Re case of ReBe22. μSR results suggest that the rhenium presence and its amount are two key factors for the appearance and the extent of TRS breaking in Re-based superconductors. Besides summarizing the existing findings, we also put forward future research ideas regarding the exciting field of materials showing TRS breaking.
Highlights
The combination of intriguing fundamental physics with far-reaching potential applications has made unconventional superconductors one of the most studied classes of materials
Such local-pairing mechanism may occur in ReT superconductors, since rhenium too can be magnetic [91, 92]. This consideration is in good agreement with the observation that TRS breaking depends on Re content, but not on a noncentrosymmetric crystal structure. In this short review we focused on recent experimental studies of ReT superconductors, where time-reversal symmetry breaking effects are often present and whose superconductivity can, be considered as unconventional
Due to its high sensitivity to the weak internal fields associated with TRS breaking, μSR represents one of the key techniques in the search for TRS-breaking effects in the superconducting state
Summary
The combination of intriguing fundamental physics with far-reaching potential applications has made unconventional superconductors one of the most studied classes of materials. Owing to the strong correlation and the interplay between d- and f-electrons, these materials often exhibit rich magnetic and superconducting properties Since their superconductivity is most likely mediated by spin fluctuations, this implies an unconventional (i.e., non phonon-related) pairing mechanism. The other class consists mainly of weakly correlated materials, which are free of “magnetic” f-electrons, as e.g., LaNiC2, La7Ir3, CaPtAs, or ReT (T 3d-5d early transition metals) [14,15,16,17,18,19,20] Their superconductivity is not mediated by the electrons’ spin fluctuations. In the last section, we outline some possible future research directions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
