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arXiv · 1905.12740

Melting of charge order in the low-temperature state of an electronic ferroelectric

Nora M. Hassan·Komalavalli Thirunavukkuarasu·Zhengguang Lu·Dmitry Smirnov·Elena I. Zhilyaeva·Svetlana Torunova·Rimma N. Lyubovskaya·Natalia Drichko
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Abstract

Strong electronic interactions can drive a system into a state with a symmetry breaking. Lattice frustration or competing interactions tend to prevent a symmetry breaking, leading to quantum disordered phases. In spin systems frustration can produce a spin liquid state. Frustration of a charge degree of freedom also can result in various exotic states, however, experimental data on these effects is scarce. In this work we demonstrate how a charge ordered ferroelectric looses the order on cooling to low temperatures using an example of a Mott insulator on a weakly anisotropic triangular lattice $κ$-(BEDT-TTF)$_2$Hg(SCN)$_2$Cl. Typically, a low temperature ordered state is a ground state of a system, and the demonstrated re-entrant behavior is unique. Raman scattering spectroscopy finds that this material enters an insulating ferroelectric `dipole solid' state at $T=30~K$, but below $T=15~K$ the order melts, while preserving the insulating energy gap. The resulting phase diagram is relevant to other quantum paraelectric materials.

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Nora M. Hassan, Komalavalli Thirunavukkuarasu, Zhengguang Lu, Dmitry Smirnov, Elena I. Zhilyaeva, Svetlana Torunova, Rimma N. Lyubovskaya, Natalia Drichko. 2019-05-29. Melting of charge order in the low-temperature state of an electronic ferroelectric. https://doi.org/10.1038/s41535-020-0217-5

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