Critical current density and vortex pinning mechanism of Li_x(NH₃)_yFe₂Te${}_{1.2}$Se${}_{0.8}$ single crystals

Abstract

Abstract.We grew Li x (NH 3 ) y Fe 2 Te 1.2 Se 0.8 single crystals successfully using the lowtemperature ammonothermal method and the onset superconducting transition temperature T onset c is increased to 21 K when compared to 14 K in the parent compound FeTe 0.6 Se 0.4 . The derived critical current density J c increases remarkably to 2.6×10 5 A/cm 2 at 2 K. Further analysis indicates that the dominant pinning mechanism in Li x (NH 3 ) y Fe 2 Te 1.2 Se 0.8 single crystal is the interaction between vortex and surfacelike defects with normal core, by variations in the charge-carrier mean free path l near the defects (δl pinning). Moreover, the flux creep is important to the vortex dynamics of this material.

Significant enhancement of critical current density in H+-intercalated FeSe single crystal

“…As shown in figure 3(a), f P of pristine FeSe can be well fitted by equation ( 1) from 2 to 6 K, suggesting that the pinning mechanism is dominated by the normal point pinning. In contrast, H x -FeSe in figure 3(b) is well described by equation ( 2), indicating dominance of the surface pinning, as observed in FeS [48], (Li 1−x Fe x )OHFeSe [25] and Li x (NH 3 ) y Fe 2 Te 1.2 Se 0.8 single crystals [30]. This result suggests that H + protonation introduces surface-like pinning centers, which results in the enhancement of J c and F p .…”

“…The largest J c in (Li 1−x Fe x )OHFeSe single crystal reaches a value about 7 × 10 5 A cm −2 at 5 K [25,26]. Some other studies on J c have also been carried out in K x Fe 2 Se 2 [27,28], Fe(Se,Te) [29] and Li x (NH 3 ) y Fe 2 Te 1.2 Se 0.8 [30] single crystals.…”

Fabricating Ba0.5Cs0.5Fe2As2 films on BaFe2As2 substrates and their superconducting properties

“…In order to comprehensively understand the pinning mechanism of the vortices, the pinning force density F p ∝ J c H can provide significant information [38,39]. As proposed by Dew-Hughes, there are several pinning mechanisms, such as normal point pinning, and surface pinning.…”

Transport properties of Lix(NH3)yFe2(TezSe1−z)2single crystals in the mixed state

“…Single crystals of LiFeSe-122 and LiFeTeSe-122 were synthesized via the low-temperature ammonothermal technique. The detailed experimental procedure and characterizations of crystals were described in previous works [18,19]. The elemental analysis was performed using the inductively coupled plasma atomic emission spectroscopy (ICP-AES) and the atomic ratio of Li x (NH 3 ) y Fe 2 (Te z Se z 1-) 2 single crystals used in this study is Li : Fe : Se=0.18 : 1 : 0.9 for z 0 = and Li : Fe : Te : Se=0.16 : 1 : 0.60 : 0.38 for z=0.6, respectively.…”