Pressure-induced superconductivity in parent CaFeAsF single crystals

Abstract

is a parent compound of the 1111 type of iron-based superconductors. It is similar to the parent LaFeAsO, but it is oxygen-free. To date, studies of pressure-induced effects have only focused on pure and doped polycrystalline CaFeAsF samples. Here, we carried out high-pressure electrical resistivity and Hall coefficient measurements up to 48.2 GPa on single crystals of CaFeAsF. The structural transition temperature T str decreased monotonically upon increasing the pressure, and reached ∼60 K at 9.6 GPa. Superconductivity emerged suddenly at 8.6 GPa with the T c,onset ∼ 25.7 K, which decreased monotonically with increasing pressure to 5.7 K under 48.2 GPa. Moreover, just after the appearance of superconductivity, the Hall coefficient at 40 K started to decrease with increasing pressure, while keeping its sign negative persisting up to 48.2 GPa.

Pressure tuning of iron-based superconductor Ca10(Pt3As8) ((Fe0.95Pt0.05)2As2)5

“…The resistivity is metallic at higher temperature, reaching a minimum at T dip and then increasing with further decreasing temperature. The low temperature upturn resembles the low pressure data of CaFeAsF parent compound [16] and also doped 1111 system [ [17][18][19][20]. The upturn becomes less pronounced with increasing pressure, which is similar to the effect of Pt doping [2].…”

“…This suggests the multiband nature of superconductivity in Ca 10 (Pt 3 As 8 )((Fe 0.95 Pt 0.05 ) 2 As 2 ) 5 under pressure. The upward curvature of H c2 (T) is also observed in the 10-4-8 phase [22] and CaFeAsF [16]. The H c2 (T) data can be described within the entire temperature range by the empirical equation H c2 (T) = H c2 (0)(1 − T/T c ) n [16,23], which gives a H c2 (0) of 14.1-17.2 T and the exponent n ranges from 1.55-1.75 in the pressure range between 1.64-4.52 GPa.…”

“…The upward curvature of H c2 (T) is also observed in the 10-4-8 phase [22] and CaFeAsF [16]. The H c2 (T) data can be described within the entire temperature range by the empirical equation H c2 (T) = H c2 (0)(1 − T/T c ) n [16,23], which gives a H c2 (0) of 14.1-17.2 T and the exponent n ranges from 1.55-1.75 in the pressure range between 1.64-4.52 GPa. The inset shows the reduced magnetic field H/H c2 (0) versus the reduced temperature T/T c0 curves.…”

Origin of superconductivity and giant phonon softening in TlInTe$_2$ under pressure

“…The experimental plot of upper critical field against temperature at 5.75 GPa and 10.1 GPa can be fitted by using the Ginzburg-Landau (G-L) equation [9,32]…”

Two-gap superconductivity in CaFe0.88Co0.12AsF revealed by temperature dependence of the lower critical field Hc1c (T)

“…Recently clear progresses were made on the single-crystal growth of the fluorine-based 1111 system of FeSCs, CaFeAsF 22 and the Co doped counterparts 23 , and systematic investigations 2 have been carried out on this system [24][25][26][27][28][29][30][31] . Especially, it was found that the smaller FS around the Γ point (see the α FS in Fig.…”