Quantum criticality in electron-doped BaFe2-xNixAs2.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Critical Phenomena

Background:

• Quantum critical points (QCPs) are fundamental to understanding exotic states of matter.
• Superconductivity in materials like cuprates and heavy fermions is often linked to QCPs.
• Iron-pnictide superconductors offer a new platform to study these phenomena.

Purpose of the Study:

• Investigate the quantum critical behavior in BaFe(2-x)Ni(x)As₂.
• Identify the nature of critical points in this material system.
• Explore the relationship between quantum criticality and superconductivity in iron pnictides.

Main Methods:

• Transport measurements to analyze electrical resistivity.
• Nuclear Magnetic Resonance (NMR) spectroscopy to probe magnetic properties.
• Systematic doping studies across a range of x in BaFe(2-x)Ni(x)As₂.

Main Results:

• Two critical points were identified at x(c1)=0.10 and x(c2)=0.14.
• Electrical resistivity exhibited a power-law dependence ρ=ρ₀+AT(n) with n≈1 near x(c1) and n≈1.1 near x(c2).
• NMR confirmed x(c1) as a magnetic QCP and suggested x(c2) is associated with a nematic structural transition.

Conclusions:

• The findings reveal distinct quantum critical points in iron-pnictide superconductors.
• The identified magnetic and nematic quantum critical points are crucial for understanding the material's properties.
• Superconductivity in carrier-doped pnictides appears closely related to these quantum critical phenomena.