Effect of pressure on the self-hole-doped superconductor RbGd₂Fe₄As₄O₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Discovery of RbGd2Fe4As4O2, a self-hole-doped stoichiometric superconductor with separated double FeAs layers.
• Exhibits a high superconducting transition temperature (Tc) of 35 K at ambient pressure.

Purpose of the Study:

• Investigate the impact of applied pressure on the superconducting transition temperature (Tc) of RbGd2Fe4As4O2.
• Analyze the evolution of normal-state transport properties under pressure.
• Explore the relationship between pressure, electronic states, and superconductivity.

Main Methods:

• Resistivity measurements (ρ(T)) were conducted under hydrostatic pressures up to 14 GPa using a cubic anvil cell.
• Analysis of the temperature dependence of resistivity to determine the exponent 'n' in the low-temperature behavior ρ(T) ∝ T^n.
• Monitoring changes in the quadratic temperature coefficient of resistivity.

Main Results:

• Superconducting transition temperature (Tc) monotonically decreases from 35 K to approximately 12.5 K at 14 GPa.
• A change in the slope of Tc(P) was observed around 4 GPa.
• A crossover from non-Fermi liquid (n=1) to Fermi liquid (n=2) behavior in the normal state occurs at pressures >= 4 GPa.
• Significant reduction in the quadratic temperature coefficient of resistivity indicates changes in effective mass.

Conclusions:

• Ambient pressure RbGd2Fe4As4O2 is likely situated near a magnetic quantum critical point (QCP), with enhanced spin fluctuations driving high Tc superconductivity.
• Applied pressure broadens electronic bandwidth and weakens spin fluctuations, suppressing Tc and restoring a Fermi liquid ground state.
• The observed non-Fermi liquid to Fermi liquid crossover provides insights into the mechanism of superconductivity in this material.