Observation of direct evolution from antiferromagnetism to superconductivity in Cu1−xLixFeAs ( 0≤x≤1.0 )

Abstract

We report the structure, antiferromagnetism, and superconductivity in $\mathrm{C}{\mathrm{u}}_{1\ensuremath{-}x}\mathrm{L}{\mathrm{i}}_{x}\mathrm{FeAs}$ ($0\ensuremath{\le}x\ensuremath{\le}1.0$) samples. A direct evolution from antiferromagnetism to superconductivity is observed as increasing doping level of Li. A phase diagram is constructed to show this evolution, which features no coexistence region between superconductivity and antiferromagnetism. This behavior shows that antiferromagnetic CuFeAs can be regarded as a parent compound to the observed superconductivity by equivalent doping, which is different from the cases with other FeAs-based superconductors. Structural analyses and first-principles calculations indicate that the anion height of $\mathrm{F}{\mathrm{e}}_{2}\mathrm{A}{\mathrm{s}}_{2}$ tetrahedral layer plays a crucial role on the physical properties. Moreover, the simple Fermi surface nesting picture adopted to explain the evolution from spin-density wave to superconductor in other FeAs-based superconductors might be not applicable to $\mathrm{C}{\mathrm{u}}_{1\ensuremath{-}x}\mathrm{L}{\mathrm{i}}_{x}\mathrm{FeAs}$.