First-principles study of magnetism, lattice dynamics, and superconductivity in LaFeSiHx

Linda Hung; Taner Yildirim

doi:10.1103/PhysRevB.97.224501

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First-principles study of magnetism, lattice dynamics, and superconductivity in LaFeSiHx

Linda Hung, Taner Yildirim

DOI 10.1103/PhysRevB.97.224501 · Physical Review B

T1

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Abstract

The structural, electronic, magnetic, and vibrational properties of LaFeSiHx for x between 0 and 1 are investigated using density functional theory calculations. We find that the electronic and magnetic properties are strongly controlled by the hydrogen concentration x in LaFeSiHx. While fully hydrogenated LaFeSiH has a striped antiferromagnetic ground state, the underdoped LaFeSiHx for x≤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. Hence, it is likely that the mechanism of superconductivity for LaFeSiHx is, like that of LaOFeAs, also unconventional. We furthermore suggest that LaFeSiHx could be a good proton conductor due to phase stability with a wide range of hydrogen concentrations x<1.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
LaFeSiH Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8	Pressure not reported	unknown
LaFeSiH Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8.5	Pressure not reported	unknown
LaFeSiH Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	0	Pressure not reported	unknown
LaFeSiH Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2	Pressure not reported	unknown
LaFeSiH Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	0.3	Pressure not reported	unknown
LaFeSiH0.75 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	0	Pressure not reported	unknown
LaFeSiH0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	0	Pressure not reported	unknown
LaFeSiH0.5 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	0	Pressure not reported	unknown
LaFeSiH0.25 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	0	Pressure not reported	unknown
LaFeSi Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	0.4	Pressure not reported	unknown
LaFeAsO Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	26	Pressure not reported	unknown