Superconducting Nd_1-EuNiO₂ thin films using in situ synthesis

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Chemistry

Background:

• Infinite-layer nickelates (RNiO2) are a class of materials exhibiting superconductivity.
• Superconductivity in these materials is typically induced via an ex situ reduction process.
• Europium (Eu) doping in neodymium nickel oxide (NdNiO2) has not been extensively studied for superconductivity.

Purpose of the Study:

• To investigate superconductivity in Eu-doped NdNiO2 (Nd$_{1-x}$Eu$_x$NiO$_2$).
• To develop an alternative in situ reduction method for achieving superconductivity.
• To explore the effect of Eu 4f doping on superconducting properties.

Main Methods:

• All-in situ molecular beam epitaxy (MBE) reduction process.
• Synthesis of Nd$_{1-x}$Eu$_x$NiO$_2$ thin films.
• Surface characterization using step-terrace structure analysis.
• Measurement of superconducting transition temperature (Tc) and upper critical field.

Main Results:

• Superconducting phase achieved in Nd$_{1-x}$Eu$_x$NiO$_2$ using in situ MBE reduction.
• Observed a Tc onset of 21 K at x = 0.25.
• Samples exhibited a step-terrace surface morphology.
• A large upper critical field was measured, potentially linked to Eu 4f doping.

Conclusions:

• Successful induction of superconductivity in Nd$_{1-x}$Eu$_x$NiO$_2$ via an in situ MBE reduction process.
• Eu doping and the in situ method provide an alternative to ex situ CaH2 reduction for infinite-layer nickelates.
• The observed properties suggest a correlation between Eu 4f doping and enhanced superconducting characteristics.