2D Polar Supercrystal Phase in Lacunar Spinels

Non-centrosymmetric lacunar spinels like GaMo₄S₈ host an exotic, Jahn-Teller effect driven polar state lacking antiphase ferroelectric domains at low temperature. Our preliminary cryogenic transmission electron microscopy data suggest that these domains form a 2D polar supercrystal state in thin GaMo₄S₈ lamellae. Here, we propose an in-situ scanning X-ray diffraction microscopy (SXDM) study of GaMo₄S₈ lamellae as a function of temperature to investigate the emergence of periodic domain patterns. Using ID01 at ESRF, we aim to spatially resolve the local lattice distortions and domain tilts, providing direct evidence of this new supercrystal structure emerging in polar non-ferroelectric materials.

诸如GaMo₄S₈之类的非中心对称空隙尖晶石（lacunar spinels），在低温下呈现出由姜-泰勒效应（Jahn-Teller effect）驱动的新奇极化态，且不存在反相铁电畴。我们的初步低温透射电子显微术（cryogenic transmission electron microscopy）数据表明，在薄层GaMo₄S₈样品中，此类畴可形成二维极化超晶体态。本研究拟开展GaMo₄S₈薄片的原位扫描X射线衍射显微术（scanning X-ray diffraction microscopy, SXDM）变温研究，以探究周期性畴结构的形成过程。依托欧洲同步辐射装置（European Synchrotron Radiation Facility, ESRF）的ID01光束线，我们旨在实现局域晶格畸变与畴倾斜的空间分辨，为这类极化非铁电材料中出现的新型超晶体结构提供直接实验证据。