First-principles study of magnetism, lattice dynamics, and superconductivity in LaFeSiH${}_x$

Abstract

The structural, electronic, magnetic, and vibrational properties of LaFeSiH${}_x$ for $x$ between 0 and 1 are investigated using density functional calculations. We find that the electronic and magnetic properties are strongly controlled by the hydrogen concentration $x$ in LaFeSiH${}_x$. While fully hydrogenated LaFeSiH has a striped antiferromagnetic ground state, the underdoped LaFeSiH${}_x$ for $x\le 0.75$ is not magnetic within the virtual crystal approximation or with explicit doping of supercells. The antiferromagnetic configuration breaks the symmetry of Fe $d$ orbitals and increases electron-phonon coupling up to $50\%$, especially for modes in the 20-50 meV range that are associated with Fe atomic movement. We find competing nearest and next-nearest neighbor exchange interactions and significant spin-phonon coupling, qualitatively similar but smaller in magnitude compared those found in LaOFeAs superconductors. The superconducting $T_c$ for antiferromagnetic LaFeSiH${}_x$, assuming conventional superconductivity via McMillan's equation, therefore is computed to be 2-10 K, in contrast to $T_c\approx 0$ for the nonmagnetic material. We also predict that the LaFeSiH${}_x$ could be a good proton conductor due to phase stability with a wide range of hydrogen concentration $x<1$.

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Cited by in corpus (4)

• Evidence of nodal superconductivity in LaFeSiH
• Influence of hydrogenation on the vibrational density of states of magnetocaloric ${\mathrm{LaFe}}_{11.4}{\mathrm{Si}}_{1.6}{\mathrm{H}}_{1.6}$
• Magnetic and structural properties of the iron silicide superconductor LaFeSiH
• Magnetic competition in iron-based germanide and silicide superconductors