Anisotropic upper critical field and possible Fulde-Ferrel-Larkin-Ovchinnikov state in the stoichiometric pnictide superconductor LiFeAs

Angular-dependent upper critical field of overdoped Ba(Fe1−xNix)2Murphy1, Tanatar2, Graf3 et al. 2013Phys. Rev. BSelf Cite235150View full textAdd to dashboardCite

“…(1) can be naturally explained by violation of this procedure. In addition, for iron-pnictides the importance of the paramagnetic effects for magnetic fields parallel to the Fe-As plane was suggested to explain unusual shape of the H c2 (T ) 32,60,65 ). This may also lead to the deviation from Eq.…”

“…These high values may come from strong coupling nature of superconductivity in iron pnictides, or indeed reflect paramagnetic limiting at low temperatures as was suggested in several studies. 32,60,74 V. CONCLUSIONS By performing high angular resolution study of the upper critical field in two overdoped compositions of iron pnictide superconductor Ba(Fe 1−x Ni x ) 2 As 2 , we find clear deviations from the anisotropic Ginzburg-Landau form. Implementing linearization plot analysis of our and previously published data, we find clear deviations from the form only in the case of clean fully -gapped multi-band superconductors, such as NbSe 2 ang MgB 2 , but not in dirty MgB 2 and not clean KFe 2 As 2 .…”

“…The upper critical fields of iron pnictides are very high, 30 and besides the potential for high field applications, 31 this brings the possibility of the paramagnetic effects at low temperatures. 32 Since Fe-As layers form a main building block of all iron-based superconductors, [33][34][35][36] these compounds show anisotropy of the electronic structure, reflected in the anisotropy γ H of the upper critical field. Unlike signature layered materials, organic superconductors 37 and cuprates, 38 the values of γ H in iron arsedines are small, for most compounds in the range 2 to 4, 39-48 with few exceptions [49][50][51] were values as high as 7 to 10 are found, see Ref.…”

Multiple phase transitions in Pauli-limited iron-based superconductors

“…[19] reported possibly the FFLO phase in the multi-band iron-based superconductor KFe 2 As 2 . Although it should be noted that hints about the FFLO phase in pnictides had been reported in other experimental [20][21][22][23][24][25] and theoretical [26] works previously.…”

Pauli-limiting effects in the upper critical fields of a clean LiFeAs single crystal

“…37 The LiFeAs by the Sn-flux method should be therefore distinguished from the case of the Sn-flux grown BaFe 2 As 2 where high quality specimens could not be well obtained. 38 Due to the hygroscopic nature of LiFeAs, the sample was covered with a Stycast™ epoxy after making electric contacts with a silver epoxy (Epotek TM ) to the single crystal's surface inside the glove box.…”