元素铋薄膜中的量子度量四极矩
Quantum metric quadrupoles in elemental bismuth thin films
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中文总结 AI 辅助
研究含相对论费米子的中心对称材料中三阶输运，发现由量子度量四极矩（QMQs）控制，其可源于不同量子几何结构。通过铋薄膜实验验证，揭示量子度量在多晶系统中作用，确立三阶非线性输运为波函数几何高精度诊断工具。
中文摘要 AI 辅助
固体的非线性输运性质深深植根于其电子波函数的量子几何结构，该结构由量子几何张量编码。其实部，即量子度量，最近被认为是量子材料中非线性输运的主要起源，在时间反演和空间反演对称性不同时存在的情况下。因此，量子度量对最大一类材料——非磁性和中心对称系统——的影响仍然完全未知。在这里，我们证明了在含有相对论费米子的中心对称材料中，三阶输运由量子度量四极矩（QMQs）控制。我们表明，这些QMQs可以起源于体三维狄拉克费米子的非阿贝尔量子几何结构和自旋轨道耦合表面态的阿贝尔量子几何结构。与迄今为止已知的所有零场非线性输运特征形成鲜明对比的是，即使在高度可扩展的多晶薄膜中，由这些QMQs驱动的电流也作为一种稳健、非零的可观测量持续存在。我们通过测量元素铋薄膜中的非线性输运，观察到一种稳健、表面主导且宽带的三次谐波产生，这种产生一直持续到室温，从而实验验证了这种量子度量足迹。我们的发现揭示了量子度量在多晶系统中的隐藏作用，将三阶非线性输运确立为在环境条件下波函数几何结构的高精度诊断工具。
英文摘要
The nonlinear transport properties of solids are deeply rooted in the quantum geometry of their electronic wavefunctions, which is encoded in the quantum geometric tensor. Its real part, known as the quantum metric, has been recently identified as a primary origin of nonlinear transport in quantum materials where time-reversal and inversion symmetries are not simultaneously present. Consequently, the influence of the quantum metric on the largest class of materials -- non-magnetic and centrosymmetric systems -- has remained entirely elusive. Here, we demonstrate that third-order transport in centrosymmetric materials hosting relativistic fermions is governed by quantum metric quadrupoles (QMQs). We show that these QMQs can originate from both the non-Abelian quantum geometry of bulk three-dimensional Dirac fermions and the Abelian quantum geometry of spin-orbit-coupled surface states. In stark contrast to all zero-field nonlinear transport signatures known to date, the current driven by these QMQs persists as a robust, non-vanishing observable even in highly scalable polycrystalline thin films. We experimentally validate this quantum metric footprint by measuring nonlinear transport in thin films of elemental bismuth, observing a robust, surface-dominated, and broadband third-harmonic generation that persists up to room temperature. Our findings uncover a hidden role of the quantum metric in polycrystalline systems, establishing third-order nonlinear transport as a high-precision diagnostic tool of wavefunction geometry under ambient conditions.
