发表机构
California Institute of Technology; The Ohio State University（加州理工学院; 俄亥俄州立大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过外延固态脱合金在La-Ag-Ge薄膜中实现局域对称性破缺，获得亚稳态超导相，为相选择性合成提供新途径。
AI 中文摘要
亚稳态量子材料通常占据狭窄的成分窗口，其局域对称性与竞争的平衡结构不同。这些特征为在相似的化学子空间内实现性质全新的电子特性开辟了途径，同时也使其确定性合成变得复杂。本文展示了在La-Ag-Ge化学空间中利用外延三元薄膜进行生长后固态脱合金过程，以实现衍射平均的中心对称超导结构。该过程通过在800-900°C退火过程中净Ag损失，将极性$P6_3mc$-LaAgGe转变为衍射平均的中心对称AlB$_2$型$P6/mmm$ La-Ag-Ge。原子分辨率电子显微镜揭示了相对于平面构型的正负两种Ag-Ge位移，这与局域反演对称性破缺畸变一致。转化后的薄膜表现出成分依赖的超导性，临界温度低于1 K，在最薄超导薄膜中面内上临界场超过弱耦合Pauli场估计值约6倍。这些结果确立了外延固态脱合金作为亚稳态相相选择性合成的途径，提供了对原子尺度结构构型及其与涌现电子特性相互作用的控制。
英文摘要
Metastable quantum materials often occupy narrow composition windows with local symmetries distinct from competing equilibrium structures. These features open pathways for realizing qualitatively new electronic properties within a similar chemical subspace while at the same time complicating their deterministic synthesis. Here we illustrate a post-growth solid-state dealloying process using epitaxial ternary thin films in the La--Ag--Ge chemical space to realize a diffraction-averaged centrosymmetric superconducting structure. The process converts polar $P6_3mc$-LaAgGe into diffraction-averaged centrosymmetric AlB$_2$-type $P6/mmm$ La-Ag-Ge through net Ag loss during annealing at 800--900 $^\circ$C. Atomic-resolution electron microscopy reveals local Ag--Ge displacements of both signs relative to the planar configuration, consistent with local inversion-symmetry-breaking distortions. The converted films exhibit composition-dependent superconductivity with critical temperatures below 1 K and in-plane upper critical fields that exceed the weak-coupling Pauli-field estimate by a factor of approximately 6 in the thinnest superconducting films. These results establish epitaxial solid-state dealloying as a route to phase-selective synthesis of metastable phases, offering control over atomic-scale structural configurations and their interplay with emergent electronic properties.
