Landau-Lifschitz Magnets: Exact Thermodynamics and Transport.

Area of Science:

• Condensed matter physics
• Statistical mechanics
• Quantum magnetism

Background:

• The classical Landau-Lifshitz equation is a fundamental model for ferromagnetism.
• Studying its transport phenomena, especially at finite temperatures, has been challenging.
• Integrability in one spatial dimension aids in classifying mode spectra.

Purpose of the Study:

• To develop an exact description of thermodynamic equilibrium states for the classical Landau-Lifshitz model.
• To investigate the role of interacting modes in thermodynamic and transport properties.
• To bridge the gap between classical and quantum descriptions of magnetic systems.

Main Methods:

• Utilizing the semiclassical limit of the integrable quantum spin-S anisotropic Heisenberg chain.
• Applying the thermodynamic Bethe ansatz description.
• Analyzing the mode spectrum in both axial and planar regimes.

Main Results:

• An exact characterization of thermodynamic equilibrium states in terms of interacting modes.
• Identification of solitons with unconventional statistics in the axial regime.
• Discovery of additional radiative and solitonic modes in the planar regime.
• Analytical study of unconventional transport properties, such as the spin Drude weight.

Conclusions:

• The developed framework accurately describes thermodynamic equilibrium states and enables the study of unconventional transport.
• The findings show excellent agreement with Monte Carlo simulations for the spin Drude weight.
• This work provides new insights into the physics of integrable magnetic systems.