Fluctuation-driven quantum phase transitions in clean itinerant ferromagnets.

Area of Science:

• Condensed Matter Physics
• Quantum Magnetism

Background:

• Hertz's mean-field theory is a standard approach for analyzing quantum phase transitions.
• Itinerant ferromagnets exhibit complex magnetic behaviors influenced by electron interactions.

Purpose of the Study:

• To analyze the quantum phase transition in clean itinerant ferromagnets.
• To investigate the validity of Hertz's mean-field theory in lower dimensions.
• To explore the nature and stability of predicted phase transitions.

Main Methods:

• Renormalized mean-field theory was applied.
• Renormalization group techniques were used to analyze transition stability.
• Theoretical analysis of soft particle-hole modes.

Main Results:

• Soft particle-hole modes invalidate Hertz's mean-field theory for dimensions d ≤ 3.
• A fluctuation-induced first-order transition is predicted for 1 < d ≤ 3.
• The transition can be stable or preempted by a fluctuation-induced second-order transition based on parameters.

Conclusions:

• The study provides a more accurate theoretical framework for quantum phase transitions in itinerant ferromagnets.
• Results align with recent experimental observations.
• The findings offer insights into the critical behavior and phase diagram of these magnetic systems.