利用低温量子扭转显微镜测量转角双层石墨烯中的声子色散与电子-相子耦合
Measuring Phonon Dispersion and Electron-Phason Coupling in Twisted Bilayer Graphene with a Cryogenic Quantum Twisting Microscope
AI总结：
本研究开发了低温量子扭转显微镜技术，可同时测量范德瓦尔斯材料的电子、声子色散及分辨动量和模式的电子-声子耦合，发现转角双层石墨烯中存在随转角减小耦合增强的低能相子模式，为探测多种中性集体模式提供了新方法。
摘要：
电子与声子的耦合是固体中的基本相互作用之一，是电阻率、热导率和超导性等多种现象的基础。然而，对单个声子模式的这种耦合进行直接测量仍是一项重大挑战。在本研究中，我们提出了一种绘制范德瓦尔斯材料中声子色散和电子-声子耦合（EPC）的新技术。通过将量子扭转显微镜推广至低温环境，我们证明了它不仅能够通过弹性动量守恒隧穿绘制电子色散，还能通过非弹性动量守恒隧穿绘制声子色散。关键在于，非弹性隧穿强度可直接定量测量分辨动量和模式的EPC。我们利用该技术测量了转角双层石墨烯（TBG）的声子谱和EPC。令人惊讶的是，我们发现与标准声学声子（其与电子的耦合随动量趋于零而减弱）不同，TBG存在一种低能模式，其耦合随转角减小而增强。我们表明，这种异常耦合源于莫尔系统的层反对称“相子”模式对层间隧穿的调制。本文展示的技术为探测量子材料中与电子隧穿耦合的多种其他中性集体模式（包括等离激元、磁振子和自旋子）开辟了道路。
英文摘要：
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 remains a significant challenge. In this work, we introduce a novel technique for mapping phonon dispersions and electron phonon coupling (EPC) in van der Waals materials. By generalizing the quantum twisting microscope to cryogenic temperatures, we demonstrate its capability to map not only electronic dispersions via 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). Surprisingly, we find that unlike standard acoustic phonons, whose coupling to electrons diminishes as their momentum goes 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 inter-layer tunnelling by a layer-antisymmetric 'phason' mode of the moiré system. The technique demonstrated here opens the way for probing a large variety of other neutral collective modes that couple to electronic tunnelling, including plasmons, magnons and spinons in quantum materials.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
