Iron-based superconductivity extended to the novel silicide LaFeSiH

Abstract

We report the synthesis and characterization of the novel silicide LaFeSiH displaying superconductivity with onset at 11 K. We find that this pnictogen-free compound is isostructural to LaFeAsO, with a similar low-temperature tetragonal to orthorhombic distortion. Using density functional theory we show that this system is also a multiband metal in which the orthorhombic distortion is likely related to single-stripe antiferromagnetic order. Electrical resistivity and magnetic susceptibility measurements reveal that these features occur side-by-side with superconductivity, which is suppressed by external pressure.Iron-based superconductors (Fe-based SCs) provide an unprecedented playground for the investigation of high-T c superconductivity. These systems belong to a huge family of compounds and recurrently display the following key features (see e.g. [1,2] for recent reviews). From the structural point of view, they have FeX layers in which the Fe atoms form a square lattice that is sandwiched between two ( √ 2 × √ 2)R45 • shifted lattices of X (= P, As, Se, Te, S). This leads to a quasi-2D multiband Fermi surface that mainly originates from the Fe 3d orbitals. In addition, the parent compounds often display anti-ferromagnetic (AFM) order inducing a lattice distortion [3][4][5] that is generally pre-empted by the so-called nematic transition [2]. In the prototypical case of RFeAsO (R = rare earth), for example, this specifically corresponds to single-stripe AFM order [also called (π, 0) order] and a square-to-rectangular distortion of the Fe layers. These features advocate for the so-called s ± superconducting gap symmetry and a spin-fluctuation pairing. This superconductivity can be induced by carrier doping resulting from either chemical substitutions or physical pressure [6]. From a more methodological point of view, the electronic band structure and the magnetic orders found in Fe-based SC can be reasonably well described by means of DFT-based calculations as the electronic correlations often remain relatively weak.

Effect of Carbon Insertion on the Structural and Magnetic Properties of NdScSi

“…The approximate c parameter for each of these peaks was calculated and, as well as the two labelled c parameters (15.3948 and 15.4122 Å) that yield effective x values of 0.48(2) and 0.44(2) respectively, there is an additional small shoulder at lower angles. This peak is indexed with c = 15.4428 Å which corresponds to x = 0.39 (2) (Figure 3), in good agreement with the observed TC (by Figure 7 (c)). Thus the carbon is inhomogeneously distributed throughout the sample which is likely due to the large sample volume needed for neutron diffraction.…”

Study of the structural transition and hydrogenation of CeTiGe

“…Among the changes observed one can cite the transitions from antiferromagnetic to intermediate valence behavior for CeCoSi and CeCoSiH, respectively [10][11], from heavy fermion (CeRuSi) to antiferromagnetic behavior for CeRuSiH [12,13] and the huge influence of hydrogenation on the antiferromagnetic properties of the Ndand Mn-substructures of NdMnSi [4]. Very recently, the new hydride LaFeSiH, obtained through hydrogen insertion in the Pauli paramagnetic phase LaFeSi [5], displays superconductivity with onset at 11 K [14].…”

Magnetic competition in iron-based germanide and silicide superconductors

“…Consequently, the complete As → Si substitution ends up into a hole over-doping that not only introduces a strong FM tendency, but also even changes the nature of the magnetic ground state III. Energy difference with respect to the non-spin-polarized calculation and corresponding value of the Fe magnetic moment for different magnetic orders in LaFeSiO (this work) and LaFeSiH (from [6]). The energy of magnetic ground state is indicated in bold.…”

“…However, there are two notable exceptions to this rule. Namely, the 122 germanide YFe 2 Ge 2 with superconducting transition temperature T c 1.8 K [5], and the novel 1111 silicide hydride LaFeSiH displaying the second highest T c 11 K among the 1111 parent compounds [6]. In this paper, we examine how these intriguing Fe-based superconducting variants manage to run away from ferromagnetism.…”