Large Diamagnetism and Electromagnetic Duality in Two-Dimensional Dirac Electron System

Area of Science:

• Solid-state physics
• Quantum materials
• Organic conductors

Background:

• Dirac electron systems in solids simulate relativistic quantum physics.
• Conventional electrons in solids show bifurcated electric and magnetic responses due to nonrelativistic effects.
• Unified electromagnetic responses are anticipated in systems mimicking relativistic quantum physics.

Purpose of the Study:

• To investigate the electromagnetic responses of a new 2D Dirac organic conductor, α-(bis(ethylenedithio)tetraselenafulvalene)2I3 (α-(BETS)2I3).
• To explore the potential revival of electromagnetic duality in solid-state systems.
• To understand the relationship between electrical conductivity and orbital diamagnetism in this material.

Main Methods:

• Synthesis and characterization of the novel 2D Dirac organic conductor, α-(BETS)2I3.
• Measurement of electrical conductivity as a function of temperature.
• Measurement of orbital diamagnetism along the interplane direction.

Main Results:

• α-(BETS)2I3 exhibits a large orbital diamagnetism exclusively along the interplane direction.
• A nearly temperature-independent electrical conductivity of approximately e²/h per plane was observed.
• The orbital diamagnetism was found to scale with electrical conductivity over a wide temperature range.

Conclusions:

• The observed phenomena in α-(BETS)2I3 demonstrate a revival of electromagnetic duality in a solid-state system.
• This duality, typically confined to relativistic frameworks, is shown to be compatible with Maxwell's equations in this material.
• The findings bridge the gap between relativistic quantum physics and condensed matter phenomena in organic conductors.