Magnetic field-induced intermediate quantum spin liquid with a spinon Fermi surface

Area of Science:

• Condensed Matter Physics
• Quantum Magnetism
• Topological Phases of Matter

Background:

• The Kitaev model describes a quantum spin liquid (QSL) state, a novel phase of matter with exotic properties.
• Understanding phase transitions in QSLs under external fields is crucial for exploring their potential applications.

Purpose of the Study:

• To investigate the phase transitions of the Kitaev model under an applied magnetic field.
• To identify the nature of the intermediate phase and characterize its properties.

Main Methods:

• Density matrix renormalization group (DMRG) method applied to large honeycomb clusters.
• Analysis of static spin-spin correlations, magnetization, spin susceptibility, specific heat, and entropy.

Main Results:

• Two magnetic field-induced transitions were observed in the Kitaev model.
• The intermediate phase was identified as a gapless U(1) quantum spin liquid (QSL).
• The spin structure function and Fermi surface of gapless spinons were determined.

Conclusions:

• The study elucidates the field-dependent phase diagram of the Kitaev model.
• The findings confirm the existence and characteristics of a gapless U(1) QSL phase.
• The results provide insights into the behavior of quantum spin liquids in magnetic fields.