The anomaly Cu doping effects on LiFeAs superconductors

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity Research

Background:

• Investigating the effects of elemental substitution on the superconducting properties of iron-based superconductors is crucial for understanding their underlying mechanisms.
• Lithium iron arsenide (LiFeAs) is a prominent iron-based superconductor whose properties can be tuned by substituting constituent elements.

Purpose of the Study:

• To investigate the impact of copper (Cu) substitution on the superconductivity and electronic structure of LiFeAs.
• To compare the effects of Cu substitution with those of cobalt (Co) and nickel (Ni) substitutions in LiFeAs.

Main Methods:

• Experimental study of Cu-substituted LiFeAs samples.
• Analysis of lattice parameter changes, specifically the c-axis lattice constant.
• Angle-resolved photoemission spectroscopy (ARPES) to probe Fermi surface (FS) topology and electronic band structure.

Main Results:

• Cu substitution results in a significantly slower shrinking rate of the c-axis lattice parameter compared to Co/Ni substitution.
• ARPES measurements reveal nearly identical electron and hole Fermi surface sizes between undoped and Cu-substituted LiFeAs.
• A minor hole band shift below the Fermi level is observed with Cu doping, indicating a limited doping effect at the Fermi surface.

Conclusions:

• Copper substitution has a minimal carrier doping effect on the Fermi surface of LiFeAs.
• The observed effects of Cu substitution contrast sharply with the more substantial carrier doping induced by Ni or Co substitution.
• Understanding these differences is key to elucidating the relationship between electronic structure and superconductivity in LiFeAs.