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arXiv · 2607.03363

Pressure-Driven Structural Transitions without a Displacive Charge-Density Wave in La$_2$SmNi$_2$O$_7$

J. Huang·Sitaram Ramakrishnan·P. Rodière·P. Toulemonde·Z. Rahmany·V. Balédent·B. Vignolle·Sourav Marik·P. Fertey·P. Foury-Leylekian
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Abstract

We investigated the structural properties of bilayer nickelate La$_2$SmNi$_2$O$_7$ as a function of pressure and temperature. At ambient conditions, we show that the material crystallizes as a monoclinic superstructure distinct from the one previously reported and close to the pseudo-orthorhombic structure of pristine La$_3$Ni$_2$O$_7$. No signatures of satellite reflections associated with charge density wave (CDW) ordering are detected at low temperature. Upon compression, a sequence of pressure-induced structural transitions from monoclinic to orthorhombic 15 GPa and then tetragonal 21 GPa symmetry is observed. Within the superconducting dome, the quality of the X-ray diffraction data enables structural refinements enabling theoretical models to understand the emergence of superconductivity.

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J. Huang, Sitaram Ramakrishnan, P. Rodière, P. Toulemonde, Z. Rahmany, V. Balédent, B. Vignolle, Sourav Marik, P. Fertey, P. Foury-Leylekian. 2026-07-03. Pressure-Driven Structural Transitions without a Displacive Charge-Density Wave in La$_2$SmNi$_2$O$_7$. https://arxiv.org/abs/2607.03363

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