Li Jiarui, Lee Yonghun, Choi Yongseong, Kim Jong-Woo, Thompson Paul, Crust Kevin J, Xu Ruijuan, Hwang Harold Y, Ryan Philip J, Lee Wei-Sheng
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA.
Department of Applied Physics, Stanford University, Stanford, CA, USA.
Nat Commun. 2025 May 13;16(1):4445. doi: 10.1038/s41467-025-59517-4.
Mechanical strain presents an effective control over symmetry-breaking phase transitions. In quantum paraelectric SrTiO, strain can induce ferroelectric order via modification of the local Ti potential energy landscape. However, brittle bulk materials can only withstand limited strain range (~0.1%). Taking advantage of nanoscopically-thin freestanding membranes, we demonstrate an in-situ strain-induced reversible ferroelectric transition in freestanding SrTiO membranes. We measure the ferroelectric order by detecting the local anisotropy of the Ti 3d orbital signature using X-ray linear dichroism at the Ti-K pre-edge, while the strain is determined by X-ray diffraction. With reduced thickness, the SrTiO membranes remain elastic with >1% tensile strain cycles. A robust displacive ferroelectricity appears beyond a temperature-dependent critical strain. Interestingly, we discover a crossover from a classical ferroelectric transition to a quantum regime at low temperatures, which enhances strain-induced ferroelectricity. Our results offer new opportunities to strain engineer functional properties in low dimensional quantum materials and provide new insights into the role of ferroelectric fluctuations in quantum paraelectric SrTiO.
机械应变对对称性破缺的相变具有有效的控制作用。在量子顺电体SrTiO₃中，应变可通过改变局部Ti势能态势诱导铁电有序。然而，脆性块状材料只能承受有限的应变范围（约0.1%）。利用纳米尺度的独立薄膜，我们展示了在独立的SrTiO₃薄膜中由应变原位诱导的可逆铁电转变。我们通过在Ti-K吸收边前使用X射线线性二色性检测Ti 3d轨道特征的局部各向异性来测量铁电有序，而应变则通过X射线衍射确定。随着厚度减小，SrTiO₃薄膜在拉伸应变循环大于1%时仍保持弹性。在一个与温度相关的临界应变之上会出现稳健的位移型铁电性。有趣的是，我们发现在低温下从经典铁电转变到量子 regime 的交叉，这增强了应变诱导的铁电性。我们的结果为在低维量子材料中通过应变工程调控功能特性提供了新机会，并为量子顺电体SrTiO₃中铁电涨落的作用提供了新见解。 （注：原文中“quantum regime”这里“regime”不太明确准确意思，暂保留英文）
