Evidence for a spinon Fermi surface in a triangular-lattice quantum-spin-liquid candidate

Area of Science:

• Condensed Matter Physics
• Quantum Materials

Background:

• Quantum spin liquids are exotic states of matter with highly entangled spins, remaining disordered at absolute zero temperature.
• These states are crucial for understanding quantum matter and have potential applications in high-temperature superconductivity and quantum information.
• Theoretical models predict fractionalized spin excitations called spinons in quantum spin liquids.

Purpose of the Study:

• To experimentally identify a quantum spin liquid state in the triangular-lattice antiferromagnet YbMgGaO4.
• To characterize the spin excitations in YbMgGaO4 using neutron scattering.

Main Methods:

• Neutron scattering measurements were performed on YbMgGaO4.
• Analysis focused on the characteristics of spin excitations across the Brillouin zone.

Main Results:

• Broad spin excitations were observed across a wide region of the Brillouin zone.
• A diffusive spin excitation was detected persisting at low energies with a distinct upper excitation edge.
• These findings are consistent with the particle-hole excitation of a spinon Fermi surface.

Conclusions:

• The results strongly suggest the existence of a quantum spin liquid state in YbMgGaO4.
• This material features a spin-1/2 triangular lattice, aligning with theoretical proposals for quantum spin liquids.
• The observed spinon Fermi surface provides key evidence for this exotic quantum state.