In:
Chinese Physics B, IOP Publishing, Vol. 28, No. 6 ( 2019-06-01), p. 067401-
Abstract:
Heavy electron-doped FeSe-derived materials have attracted attention due to their uncommon electronic structures with only ‘electron pockets’, and they are different from other iron-based superconductors. Here, we report the crystal structures, superconductivities and normal state properties of two new Li-doped FeSe-based materials, i.e. , Li 0.15 (C 3 H 10 N 2 ) 0.32 FeSe ( P -4) and Li x (C 3 H 10 N 2 ) 0.32 FeSe ( P 4/ nmm , 0.25 〈 x 〈 0.4 ) with superconducting transition temperatures ranging from 40 K to 46 K. The determined crystal structures reveal a coupling between Li concentration and the orientation of 1,3-diaminopropane molecules within the largely expanded FeSe layers. Superconducting fluctuations appear in the resistivity of the two superconductors and are fitted in terms of the quasi two-dimensional (2D) Lawrence–Doniach model. The existence of a crossing point and scaling behavior in the T -dependence of diamagnetic response also suggests that the two superconductors belong to the quasi-2D system. Interestingly, with the increase of temperature, a sign of Hall coefficient ( R H ) reversing from negative to positive is observed at ∼185 K in both phases, suggesting that ‘hole pockets’ emerge in these electron-doped FeSe materials. First principle calculations indicate that the increase in FeSe layer distance will lift up a ‘hole band’ associated with d x 2 − y 2 character and increase the hole carriers. Our findings suggest that the increase in two dimensionalities may lead to the sign-reversal Hall resistivity in Li x (C 3 H 10 N 2 ) 0.32 FeSe at high temperature.
Type of Medium:
Online Resource
ISSN:
1674-1056
DOI:
10.1088/1674-1056/28/6/067401
Language:
Unknown
Publisher:
IOP Publishing
Publication Date:
2019
detail.hit.zdb_id:
2412147-2
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