La₂PrNi₂O₇薄膜中压缩应变诱导的类电子高温超导电性
Electron-like high-temperature superconductivity induced by compressive strain in La2PrNi2O7 thin films
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中文总结 AI 辅助
本研究通过臭氧辅助原子层外延法制备不同应变的La₂PrNi₂O₇薄膜，发现极端压缩应变可诱导类电子高温超导电性，揭示其与高压体材超导机制的电子二分性，为研究镍酸盐多轨道物理提供新平台。
中文摘要 AI 辅助
在外延压缩应变下实现双层镍酸盐的高温超导电性被广泛认为是在模拟高静水压的效果，为验证这些机制是否等价，本研究探究了从压缩（-2.14%）到拉伸（+0.91%）的完整应变范围。关键的是，通过臭氧辅助原子层外延法，在NdAlO₃衬底上制备了原生La₂PrNi₂O₇薄膜，该衬底可在该材料体系中诱导最极端的压缩应变。在-2.14%的极端压缩下，这些薄膜的起始转变温度Tc_onset为60 K，33 K时呈现零电阻，20 K时具有抗磁响应，磁输运测量证实其为准二维超导特性。将所得相图与已报道数据对比发现，二者的晶格响应存在显著差异：与加压晶体不同，外延薄膜的超导窗口在面外参数c（或c/ap比值）上显著偏离，而在面内参数ap上与体材保持一致。尽管两个体系的超导电性均源于自旋密度波（SDW）的抑制，但霍尔测量揭示了根本的电子二分性：最优超导薄膜本质为类电子（霍尔系数为负），这与高压体材晶体的类空穴（霍尔系数为正）及非超导拉伸薄膜形成鲜明对比。最终，两种调控策略均能有效调制作为超导电性真正驱动因素的关联背景，突破了特定费米表面拓扑的限制。本研究建立了用于探究镍酸盐多轨道物理的宏观平台，为研究高温超导电性提供了新维度。
英文摘要
The realization of high-temperature superconductivity in bilayer nickelates under epitaxial compressive strain is widely interpreted as mimicking the effects of high hydrostatic pressure. To test the equivalence of these mechanisms, we investigated a comprehensive strain continuum ranging from compressive (-2.14%) to tensile (+0.91%). Crucially, via ozone-assisted atomic-layer epitaxy, we realized high-temperature superconductivity in as-grown La2PrNi2O7 films on NdAlO3 substrates, which induce the most extreme compressive strain in this material system. Under extreme compression (-2.14%), these films exhibit a Tc_onset of 60 K, zero resistance at 33 K, and a diamagnetic response at 20 K, with magnetotransport measurements confirming a quasi-two-dimensional superconducting nature. Comparing our phase diagram with reported data reveals distinct lattice responses: unlike in pressurized crystals, the superconducting window in epitaxial films diverges significantly in the out-of-plane parameter c (or c/ap ratio) but remains consistent with the bulk regarding the in-plane parameter ap. Crucially, while superconductivity in both systems emerges from the suppression of spin-density waves (SDW), Hall measurements reveal a fundamental electronic dichotomy: optimal superconducting films are intrinsically electron-like (exhibiting a negative Hall coefficient), in stark contrast to the hole-like nature (positive Hall coefficient) of high-pressure bulk crystals and non-superconducting tensile films. Ultimately, both tuning strategies effectively modulate the underlying correlation landscape - the true driver of superconductivity - transcending the constraints of specific Fermi surface topologies. This work establishes a macroscopic platform for probing the multi-orbital physics of nickelates, offering a new dimension for investigating high-temperature superconductivity.
