π-electron S = ½ quantum spin-liquid state in an ionic polyaromatic hydrocarbon

Area of Science:

• Condensed Matter Physics
• Materials Science
• Organic Electronics

Background:

• Molecular solids based on carbon π-electrons are promising for exotic states like superconductivity and magnetism.
• Previous studies on alkali metal reactions with polyaromatic hydrocarbons hinted at novel electronic properties, but compound structures were unknown.

Purpose of the Study:

• To isolate and characterize binary caesium salts of phenanthrene.
• To investigate the electronic and magnetic properties of these novel molecular solids.

Main Methods:

• Isolation of binary caesium salts: Cs(C14H10) and Cs2(C14H10).
• Characterization of their electronic and magnetic properties, including magnetic susceptibility measurements.
• Analysis of the magnetic topology and spin dynamics.

Main Results:

• Cs(C14H10) and Cs2(C14H10) were isolated and identified as multiorbital strongly correlated Mott insulators.
• Cs2(C14H10) exhibits diamagnetism due to orbital polarization.
• Cs(C14H10) displays Heisenberg antiferromagnetism with a gapped spin-liquid state, showing no long-range magnetic order down to 1.8 K.

Conclusions:

• Cs(C14H10) is an excellent candidate for a spin-½ quantum-spin liquid (QSL) derived purely from carbon π-electrons.
• The findings open new avenues for designing carbon-based materials with unique quantum magnetic phenomena.
• This research advances the understanding of strongly correlated electron systems in molecular solids.