Inverse Melting of an Electronic Liquid Crystal

TL;DR

This paper reports the first experimental observation of inverse melting in an electronic liquid crystal phase within a doped lanthanum nickelate, revealing the role of interlayer coupling in this rare thermodynamic phenomenon.

Contribution

It demonstrates inverse melting of electronic liquid crystalline order in a specific compound, highlighting the significance of interlayer interactions in strongly correlated systems.

Findings

Inverse melting observed via x-ray scattering

Charge modulation driven to nematic order by spin fluctuations

Interlayer coupling explains the inverse melting transition

Abstract

Inverse melting refers to the rare thermodynamic phenomenon in which a solid melts into a liquid upon cooling, a transition that can occur only when the ordered (solid) phase has more entropy than the disordered (liquid) phase, and that has so far only been observed in a handful of systems. Here we report the first experimental observation for the inverse melting of an electronic liquid crystalline order in strontium-doped lanthanum nickelate, a compound isostructural with the superconducting cuprates, with a hole doping concentration of 1/3. Using x-ray scattering, we demonstrate that the isotropic charge modulation is driven to nematic order by fluctuating spins and shows an inverse melting transition. Using a phenomenological Landau theory, we show that this inverse melting transition is due to the interlayer coupling between the charge and spin orders. This discovery points to the importance of the interlayer correlations in the system, and provides a new perspective to study the intricate nature of the electronic liquid crystal phases in strongly correlated electronic systems, including possibly the Cu- and Fe-based high-Tc superconductors.