Spin liquid state in an organic Mott insulator with a triangular lattice

Area of Science:

• Condensed Matter Physics
• Quantum Magnetism
• Organic Conductors

Background:

• Organic Mott insulators with triangular lattices are ideal for studying frustrated quantum spin systems.
• Frustration in spin systems can lead to exotic quantum states like quantum spin liquids.
• kappa-(BEDT-TTF)2Cu2(CN)(3) serves as a model system for exploring spin frustration.

Purpose of the Study:

• To investigate the magnetic properties of the organic Mott insulator kappa-(BEDT-TTF)2Cu2(CN)(3).
• To determine if long-range magnetic ordering occurs in this frustrated quantum spin system.
• To explore the potential realization of a quantum spin liquid state.

Main Methods:

• Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy was employed.
• Static magnetic susceptibility measurements were conducted.
• Experiments were performed down to millikelvin temperatures.

Main Results:

• Static susceptibility data aligns with the spin S=1/2 antiferromagnetic triangular-lattice Heisenberg model (J ≈ 250 K).
• 1H NMR spectra showed no evidence of long-range magnetic ordering even at 32 mK.
• The absence of ordering persists despite magnetic interactions significantly larger than the experimental temperature.

Conclusions:

• A quantum spin liquid state is likely realized in kappa-(BEDT-TTF)2Cu2(CN)(3).
• This quantum spin liquid state exists in close proximity to a pressure-induced superconducting state.
• The findings contribute to understanding frustrated magnetism and novel quantum phases.