超越平衡拉曼测温：石墨烯中反斯托克斯响应的费米能级调控
Beyond Equilibrium Raman Thermometry: Fermi-Level Control of the Anti-Stokes Response in Graphene
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中文总结 AI 辅助
本研究通过实验发现石墨烯的反斯托克斯拉曼响应受费米能级调控，提出其可作为探测电子-声子耦合和非平衡声子动力学的灵敏工具。
中文摘要 AI 辅助
非平衡电子和声子布居控制着纳米器件中的热产生和耗散，然而对其直接表征仍然具有挑战性。反斯托克斯拉曼散射为声子布居和局部温度提供了灵敏的探针，尽管当电子和声子布居被驱动至非平衡状态时，其解释变得更加复杂。在此，我们研究了单层石墨烯中依赖于栅压的反斯托克斯拉曼响应，并发现反斯托克斯响应偏离了平衡声子布居所预期的行为。利用空间局域的微滴光谱电化学平台、介电背栅和化学掺杂，我们观察到当费米能级从狄拉克点调谐开时，G模反斯托克斯强度发生强烈且可逆的抑制，而斯托克斯强度基本保持不变。相比之下，斯托克斯和反斯托克斯分支的G模频率和线宽随掺杂的变化符合既有的Kohn异常图像。反斯托克斯/斯托克斯强度比在测量范围内降低数倍，并表现出显著的、依赖于栅压的功率响应，在电荷中性点具有最大灵敏度。与先前对掺杂石墨烯中非平衡载流子动力学研究的比较表明，费米能级依赖的电子相空间起着重要作用，其可影响热载流子驱动的声子布居以及电子介导的斯托克斯-反斯托克斯散射。我们的发现确立了反斯托克斯拉曼散射作为石墨烯中电子-声子耦合和非平衡声子动力学的灵敏探针。
英文摘要
Non-equilibrium electron and phonon populations govern heat generation and dissipation in nanoscale devices, yet their direct characterization remains challenging. Anti-Stokes Raman scattering provides a sensitive probe of phonon populations and local temperatures, although its interpretation becomes more complex when electronic and phononic populations are driven out of equilibrium. Here, we investigate the gate-dependent anti-Stokes Raman response of monolayer graphene and find that the anti-Stokes response deviates from that expected from an equilibrium phonon population. Using a spatially localized microdroplet spectroelectrochemical platform, dielectric back-gates, and chemical doping, we observe a strong and reversible suppression of the G-mode anti-Stokes intensity as the Fermi level is tuned away from the Dirac point, while the Stokes intensity remains essentially unchanged. By contrast, the G-mode frequency and linewidth of both the Stokes and anti-Stokes branches evolve with doping as expected from the established Kohn-anomaly picture. The anti-Stokes/Stokes intensity ratio decreases by several-fold over the measured range and displays a pronounced, gate-dependent power response with maximum sensitivity at charge neutrality. Comparison with previous studies of non-equilibrium carrier dynamics in doped graphene suggests an important role of Fermi-level-dependent electronic phase space, which can influence both hot-carrier-driven phonon populations and electronically mediated Stokes-anti-Stokes scattering. Our findings establish anti-Stokes Raman scattering as a sensitive probe of electron-phonon coupling and non-equilibrium phonon dynamics in graphene.
发表机构
- University of Chemistry and Technology in Prague（布拉格化学与技术大学）
- Institute of Physics, Czech Academy of Sciences（捷克科学院物理研究所）
- Helmholtz-Zentrum Dresden - Rossendorf（德累斯顿-罗森多夫亥姆霍兹中心）
- National Taiwan Normal University（台湾师范大学）
- Tohoku University（东北大学）
- Universidade Federal de Minas Gerais（米纳斯吉拉斯联邦大学）
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