近日，德国慕尼黑工业大学的Marc A.Wilde、Christian Pfleiderer和Johannes Knolle及其研究小组取得一项新进展。经过不懈努力，他们揭示了金属中准粒子寿命的量子振荡现象。相关研究成果已于2023年8月2日在国际权威学术期刊《自然》上发表。

该研究团队报道了三维拓扑半金属CoSi中观察到的量子振荡(QOs)现象，它在两个基本方面违背了标准描述。首先，振荡频率对应于两个波段的半经典准粒子(QP)轨道的差，因为轨迹的一半会与洛伦兹力相反，因此是被禁止的。其次，振荡存在于50K以上，与其他振荡成分在几个开尔文以下就消失形成鲜明对比。

这一研究发现与QP生命周期(QPL)的QOs的通用模型计算非常一致。因为它们存在的唯一前提是至少两个电子轨道的非线性耦合，例如，由于缺陷或集体激励上的QP散射，QPL的这种QOs对于具有多个轨道的朗道量子化的任何金属都是通用的，并可以应用于拓扑半金属、非常规超导体、稀土化合物和Rashba系统中的某些频率。这一发现允许识别和测量相关现象，例如在二维材料和多波段金属中。

据悉，经过近一个世纪的研究，关于金属的低能激发如何用非相互作用波段的有效单粒子理论来解释，仍然是一个未解之谜。在真实材料中，丰富的相互作用会引起超越有效单粒子、单波段行为的现象，这就引发了直接光谱特征问题的产生。

附：英文原文

Title: Quantum oscillations of the quasiparticle lifetime in a metal

Author: Huber, Nico, Leeb, Valentin, Bauer, Andreas, Benka, Georg, Knolle, Johannes, Pfleiderer, Christian, Wilde, Marc A.

Issue&Volume: 2023-08-02

Abstract: Following nearly a century of research, it remains a puzzle that the low-lying excitations of metals are remarkably well explained by effective single-particle theories of non-interacting bands. The abundance of interactions in real materials raises the question of direct spectroscopic signatures of phenomena beyond effective single-particle, single-band behaviour. Here we report the identification of quantum oscillations (QOs) in the three-dimensional topological semimetal CoSi, which defy the standard description in two fundamental aspects. First, the oscillation frequency corresponds to the difference of semiclassical quasiparticle (QP) orbits of two bands, which are forbidden as half of the trajectory would oppose the Lorentz force. Second, the oscillations exist up to above 50K, in strong contrast to all other oscillatory components, which vanish below a few kelvin. Our findings are in excellent agreement with generic model calculations of QOs of the QP lifetime (QPL). Because the only precondition for their existence is a nonlinear coupling of at least two electronic orbits, for example, owing to QP scattering on defects or collective excitations, such QOs of the QPL are generic for any metal featuring Landau quantization with several orbits. They are consistent with certain frequencies in topological semimetals, unconventional superconductors, rare-earth compounds and Rashba systems, and permit to identify and gauge correlation phenomena, for example, in two-dimensional materials and multiband metals.

DOI: 10.1038/s41586-023-06330-y

Source: https://www.nature.com/articles/s41586-023-06330-y