Unified picture of the doping dependence of superconducting transition temperatures in alkali metal/ammonia intercalated FeSe

Abstract

In the recently synthesized Li${}_x$(NH${}_2$)${}_y$(NH${}_3$)${}_z$Fe${}_2$Se${}_2$ family of iron chalcogenides a molecular spacer consisting of lithium ions, lithium amide and ammonia separates layers of FeSe. It has been shown that upon variation of the chemical composition of the spacer layer, superconducting transition temperatures can reach $T_c\sim 44\mathrm{K}$, but the relative importance of the layer separation and effective doping to the $T_c$ enhancement is currently unclear. Using state of the art band structure unfolding techniques, we construct eight-orbital models from ab-initio density functional theory calculations for these materials. Within an RPA spin-fluctuation approach, we show that the electron doping enhances the superconducting pairing, which is of $s_{\pm }$-symmetry and explain the experimentally observed limit to $T_c$ in the molecular spacer intercalated FeSe class of materials.

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• Using Gap Symmetry and Structure to Reveal the Pairing Mechanism in Fe-based Superconductors
• On the Remarkable Superconductivity of FeSe and its Close Cousins
• Discrete superconducting phases in FeSe-derived superconductors
• The intercalation chemistry of layered iron chalcogenide superconductors
• High Tc via spin fluctuations from incipient bands: application to monolayers and intercalates of FeSe
• Enhancement of Tc by point-like disorder and anisotropic gap in FeSe
• Superconductivity from repulsive interactions on the kagome lattice
• Near-degeneracy of extended $s+d_{x^2-y^2}$ and $d_{xy}$ order parameters in quasi-two-dimensional organic superconductors
• Extreme anisotropy and anomalous transport properties of heavily electron doped Lix(NH3)yFe2Se2 single crystals
• Evidence for eight node mixed-symmetry superconductivity in a correlated organic metal
• New Superconducting Phase of Li${}_x$(C${}_6$H${}_{16}$N${}_2$)${}_y$Fe${}_{2-z}$Se${}_2$ with $T_{\text{c}}$ = 41 K Obtained through the Post-Annealing
• Interplay of nematic and magnetic orders in FeSe under pressure
• The preparation and phase diagrams of (${}^7$Li${}_{1-x}$Fe${}_x$OD)FeSe and (Li${}_{1-x}$Fe${}_x$OH)FeSe superconductors
• Role of vertex corrections in the matrix formulation of the random phase approximation for the multiorbital Hubbard model
• Origin of the superconducting state in the collapsed tetragonal phase of KFe2As2
• Two-dome superconductivity in FeS induced by a Lifshitz transition
• Protonation-induced discrete superconducting phases in bulk FeSe single crystals
• Spin resonance in the superconducting state of Li${}_{1-x}$Fe${}_x$ODFe${}_{1-y}$Se observed by neutron spectroscopy
• Low-energy spin excitations in Li(0.8)Fe(0.2)ODFeSe superconductor studied with inelastic neutron scattering
• New Alkali-Metal- and 2-Phenethylamine-Intercalated Superconductors $A_x$(C${}_8$H${}_{11}$N)${}_y$Fe${}_{1-z}$Se ($A$ = Li, Na) with the Largest Interlayer Spacings and $T_{\mathrm{c}}$ $\sim$ 40 K
• Novel Fe-based superconductor LaFe2As2 in comparison with traditional pnictides
• Heavily Hydride-ion-doped 1111-type Iron-based Superconductors: Synthesis, Physical Properties and Electronic Structure
• Ab-initio perspective on structural and electronic properties of iron-based superconductors
• Enhanced superconducting transition temperature in hyper-interlayer-expanded FeSe despite the suppressed electronic nematic order and spin fluctuations
• Basic electronic properties of iron selenide under variation of structural parameters
• Origin of the non-monotonic variance of Tc in the 1111 iron based superconductors with isovalent doping
• Non-trivial role of interlayer cation states in iron-based superconductors
• Intercalation effect on hyperfine parameters of Fe in FeSe superconductor with Tc = 42 K
• Coexistence of magnetism and superconductivity in separate layers of the iron-based superconductor Li_{1-x}Fe_{x}(OH)Fe_{1-y}Se
• Superconductivity and Intercalation Statein the Lithium-Hexamethylenediamine-Intercalated Superconductor Li${}_x$(C${}_6$H${}_{16}$N${}_2$)${}_y$Fe${}_{2-z}$Se${}_2$: Dependence on the Intercalation Temperature and Lithium Content
• Robustness of superconductivity to structural disorder in Sr${}_{0.3}$(NH${}_2$)${}_y$(NH${}_3$)${}_{1-y}$Fe${}_2$Se${}_2$
• Synthesis of New Lithium- and Monoamine-Intercalated Superconductors Li${}_x$(C${}_n$H${}_{2n+3}$N)${}_y$Fe${}_{1-z}$Se ($n$ = 6, 8, 18) with the Dramatically Expanded Interlayer Spacing
• $\mathrm{L}{\mathrm{i}}_{\mathrm{x}}({\mathrm{C}}_5{\mathrm{H}}_5\mathrm{N}{)}_{\mathrm{y}}\mathrm{F}{\mathrm{e}}_{2-\mathrm{z}}\mathrm{S}{\mathrm{e}}_2$: a defect resilient expanded-lattice high-temperature superconductor
• Importance of Fermi surface and magnetic interactions for the superconducting dome in electron doped FeSe intercalates
• An efficient GPU algorithm for tetrahedron-based Brillouin-zone integration
• Two new parent compounds for FeSe-based superconducting phases
• Theory for doping trends in titanium oxypnictide superconductors
• Robustness of superconducting properties to transition metal substitution and impurity phases in Fe1-xVxSe
• Two-gap superconducting properties of alkaline-earth intercalated $A_x(N{H}_3)F{e}_{2}S{e}_2$ (A = Ba or Sr)
• Symmetry-breaking-induced topology in FeSe