Superconductivity Emerging from an Electronic Phase Separation in the Charge Ordered Phase of RbFe_{2}As_{2}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• RbFe2As2 is an iron-based superconductor.
• Understanding charge order is crucial for explaining superconductivity mechanisms.
• Nuclear Quadrupole Resonance (NQR) and Nuclear Magnetic Resonance (NMR) are sensitive probes of local electronic and magnetic environments.

Purpose of the Study:

• To investigate the onset and implications of charge order in RbFe2As2.
• To probe the electronic dynamics below the charge ordering temperature using NQR and NMR.
• To explore the relationship between charge order and electronic correlations, including orbital selectivity.

Main Methods:

• Performed $^{75}$As, $^{87}$Rb, and $^{85}$Rb nuclear quadrupole resonance (NQR) measurements.
• Conducted $^{87}$Rb nuclear magnetic resonance (NMR) measurements.
• Analyzed the temperature dependence of NQR spectra and nuclear spin-lattice relaxation rates.

Main Results:

• Observed a significant broadening of the $^{75}$As NQR spectrum below approximately 140 K, indicating the onset of charge order in the FeAs planes.
• Measured a power-law decrease in the $^{75}$As nuclear spin-lattice relaxation rate from 140 K down to approximately 20 K.
• Identified distinct nuclear spin dynamics below 20 K, attributed to different local electronic configurations arising from charge order, suggesting electron localization and pseudogap phenomena.

Conclusions:

• The charge order in RbFe2As2 below 140 K significantly modifies the electronic environment.
• The observed spin dynamics below 20 K are consistent with orbital-selective electronic correlations.
• These findings provide insights into the interplay between charge order, electronic correlations, and potential competing electronic phases in iron-based superconductors.