⁷⁷Se-NMR Study under Pressure on 12%-S Doped FeSe

Abstract

The 12%-S doped FeSe system has a high Tc of 30 K at a pressure of 3.0 GPa. We have successfully investigated its microscopic properties for the first time via 77 Se-NMR measurements under pressure. The antiferromagnetic (AFM) fluctuations at the optimal pressure (∼ 3 GPa) exhibited unexpected suppression compared with the AFM fluctuations at ambient pressure, even though the optimal pressure is close to the phase boundary of the AFM phase induced at the high-pressure region. In addition, we revealed that the SC phase at an applied field of 6.02 T exhibited a remarkable double-dome structure in the pressure-temperature phase diagram, unlike the SC phase at zero field.

Impact of nematicity on the relationship between antiferromagnetic fluctuations and superconductivity in FeSe0.91S0.09 under pressure

“…T c 's for H ab are shown by black arrows. The Curie-Weiss-like behavior of (1/T 1 T ) ab above the maxima can be associated with two-dimensional AFM fluctuations [17,23].…”

“…Our results indicate that the nature of AFM fluctuations changes below and above 0.5 GPa in FeSe 0.91 S 0.09 . According to Kuwayama et al [23], AFM fluctuations with different q vectors may be responsible for the two distinct SC domes. Therefore, it is important to reveal the nature of the AFM fluctuations in the different pressure ranges.…”

“…Recent resistivity measurements under high magnetic fields on FeSe 0.89 S 0.11 under pressure reported a lack of nematic quantum criticality and the presence of Fermi-liquid behavior [22]. In addition, two SC domes separated by the nematic QPT under magnetic field have been reported in FeSe 1−x S x with x = 0.12 [23] and 0.11 [22] under pressure, which was not reported in the first (crosses) denote T c at H = 0 determined by zero resistivity and the offset point, respectively, in resistivity measurements (see the Supplemental Material [24]). The AFM transition temperature (T N ) was determined by resistivity measurements (see the Supplemental Material [24]).…”

“…The solid and open squares are data from the present Rapid Communication. The values for FeSe under p were taken from Imai et al [48] and Wiecki et al [49]; for FeSe 1−x S x under ambient p from Wiecki et al [17]; for FeSe 0.88 S 0.12 under p from Kuwayama et al [23]. The black and blue lines show linear relations for AFM fluctuations with C 4 and C 2 symmetries, respectively.…”

Extended Magnetic Dome Induced by Low Pressures in Superconducting FeSe1−xSx

“…Interestingly, in FeSe, the second-order structural transition is suppressed with pressure but a first order structural transition emerges at p ≈ 1.5 GPa and persists up to 5.8 GPa [65,68]. In FeSe 1-x S x , a structural phase transition was found at ambient and high (4.9 GPa, where a magnetic dome was detected with electrical resistivity measurements) pressures but not in the intermediate pressure region [28,67]. As we observe magnetism in the intermediate pressure region, this might imply different types of magnetic order.…”