近日，以色列魏茨曼科学研究所Ilani, S.团队研究了扭曲双层石墨烯中声子的量子扭曲显微镜。相关论文于2025年4月23日发表在《自然》杂志上。

电子和声子之间的耦合是固体中的基本相互作用之一，支撑着电阻率、热导率和超导性等一系列现象。然而，直接测量单个声子模式的这种耦合仍然是一个巨大的挑战。研究组介绍了一种绘制范德华（vdW）材料中声子色散和电子-声子耦合（EPC）的新技术。通过将量子扭曲显微镜（QTM）推广到低温，证明其不仅能够通过弹性动量守恒隧穿映射电子色散，而且能够通过非弹性动量守恒隧道映射声子色散。至关重要的是，非弹性隧穿强度提供了动量和模式分辨EPC的直接和定量测量。

研究组使用该技术测量了扭曲角大于6°的扭曲双层石墨烯（TBG）的声子谱和EPC。值得注意的是，他们发现，与标准声学声子不同，TBG表现出低能模式，其耦合随着扭转角的减小而增加，标准声学声子与电子的耦合随着动量趋近于零而减弱。研究组证明，这种不寻常的耦合是由莫尔系统的层反对称“相位子”模式对层间隧穿的调制引起的。这里展示的技术为研究与电子隧穿耦合的各种其他中性集体模式开辟了道路，包括量子材料中的等离子体激元、磁振子和自旋子。

附：英文原文

Title: Quantum twisting microscopy of phonons in twisted bilayer graphene

Author: Birkbeck, J., Xiao, J., Inbar, A., Taniguchi, T., Watanabe, K., Berg, E., Glazman, L., Guinea, F., von Oppen, F., Ilani, S.

Issue&Volume: 2025-04-23

Abstract: The coupling between electrons and phonons is one of the fundamental interactions in solids, underpinning a wide range of phenomena, such as resistivity, heat conductivity and superconductivity. However, direct measurements of this coupling for individual phonon modes remain a substantial challenge. In this work, we introduce a new technique for mapping phonon dispersions and electron–phonon coupling (EPC) in van der Waals (vdW) materials. By generalizing the quantum twisting microscope1 (QTM) to cryogenic temperatures, we demonstrate its capability to map not only electronic dispersions through elastic momentum-conserving tunnelling but also phononic dispersions through inelastic momentum-conserving tunnelling. Crucially, the inelastic tunnelling strength provides a direct and quantitative measure of the momentum and mode-resolved EPC. We use this technique to measure the phonon spectrum and EPC of twisted bilayer graphene (TBG) with twist angles larger than 6°. Notably, we find that, unlike standard acoustic phonons, whose coupling to electrons diminishes as their momentum tends to zero, TBG exhibits a low-energy mode whose coupling increases with decreasing twist angle. We show that this unusual coupling arises from the modulation of the interlayer tunnelling by a layer-antisymmetric ‘phason’ mode of the moiré system. The technique demonstrated here opens the way for examining a large variety of other neutral collective modes that couple to electronic tunnelling, including plasmons2, magnons3 and spinons4 in quantum materials.

DOI: 10.1038/s41586-025-08881-8

Source: https://www.nature.com/articles/s41586-025-08881-8