Electrically-induced phase transition in $\alpha$-(BEDT-TTF)${}_2$I${}_3$: Indications for high-mobility hot charge carriers

Abstract

The two-dimensional organic conductor $\alpha$-(BEDT-TTF)${}_2$I${}_3$ undergoes a metal-insulator transition at $T_{\mathrm{CO}}=135$ K due to electronic charge ordering. We have conducted time-resolved investigations of its electronic properties in order to explore the field- and temperature-dependent dynamics. At a certain threshold field, the system switches from low-conducting to a high-conducting state, accompanied by a negative differential resistance. Our time-dependent infrared investigations indicate that close to $T_{\mathrm{CO}}$ the strong electric field pushes the crystal into a metallic state with optical properties similar to the one for $T>T_{\mathrm{CO}}$. Well into the insulating state, however, at $T=80$ K, the spectral response evidences a completely different electronically-induced high-conducting state. Applying a two-state model of hot electrons explains the observations by excitation of charge carriers with a high mobility. They resemble the Dirac-like charge-carriers with a linear dispersion of the electronic bands found in $\alpha$-(BEDT-TTF)${}_2$I${}_3$ at high-pressure. Extensive numerical simulations quantitatively reproduce our experimental findings in all details.

arXiv comment12 pages, 15 figures

References in corpus (10)

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Cited by in corpus (7)

• Molecular Quantum Materials: Electronic Phases and Charge Dynamics in Two-Dimensional Organic Solids
• Semimetallic and charge-ordered $\alpha$-(BEDT-TTF)${}_2$I${}_3$: on the role of disorder in dc transport and dielectric properties
• Unidirectional Photonic Circuit with Phase-Change Fano Resonator
• Self-Regulated Transport in Photonic Crystals with Phase-Changing Defects
• Molecular Dynamics at Electrical- and Optical-Driven Phase Transitions Time-Resolved Infrared Studies Using Fourier-Transform Spectrometers
• Temperature-dependent generalized ellipsometry of the metal-insulator phase transition in low-symmetry charge-transfer salts
• Third-order Electrical Conductivity of the Charge-ordered Organic Salt $\alpha$-(BEDT-TTF)${}_2$I${}_3$