AI 中文总结
研究超高磁场下石墨烯的红外磁光响应，通过ARPES揭示其狄拉克色散的驼峰结构，构建朗道能级模型，用集体阿尔文波模型复现极端场吸收光谱，实现相对论等离子体的二维石墨烯模拟。
AI 中文摘要
我们研究了在高达560 T的超高磁场下，4H-SiC上的n型掺杂外延石墨烯的红外磁光响应，采用单匝线圈和电磁通量压缩技术。测量得到的吸收光谱异常宽，与常规回旋共振存在显著偏差。角分辨光电子能谱（ARPES）揭示了扭曲的狄拉克色散，呈现出带有约0.2 eV能隙的“驼峰”结构。利用通过广义双层石墨烯模型提取的能带参数，我们构建了朗道能级（LL）扇形图，该图决定了N=0⁺与N=0⁻态在160-200 T附近的临界交叉。在该阈值下，光学跃迁机制发生显著转变，从电子主导的集体模式变为电子空穴协同集体激发。此外，铥光纤激光激发（ℏω₀=0.636 eV）下的极端场吸收光谱——最终在400 T附近形成强共振，在200 T处出现肩峰——可通过集体阿尔文波模型完美复现。该分析还证明了磁场诱导的子晶格势不对称参数增强（从0.10 eV增至0.12 eV），这直接表明施加的磁场进一步放大了宏观电子空穴带不对称性。最终，场诱导的能量反转产生了强相互作用、完全补偿的电子空穴等离子体。在该 regime 中阿尔文波的共振激发表明，在二维石墨烯系统内可优雅地实现与天体极端环境中相对论正负电子等离子体类似的台式模拟。
英文摘要
We investigate the infrared magneto-optical response of n-doped epitaxial graphene on 4H-SiC in ultrahigh magnetic fields up to 560~T, utilizing single-turn coil and electromagnetic flux compression techniques. The measured absorption spectra are anomalously broad, strongly deviating from conventional cyclotron resonance. Angle-resolved photoemission spectroscopy (ARPES) reveals a distorted Dirac dispersion featuring a ``camel-back" structure with an energy gap of $E_g \sim 0.2$~eV. Using the band parameters extracted via a generalized bilayer graphene model, we construct a Landau level (LL) fan chart that dictates a critical level crossing between the $N=0^+$ and $N=0^-$ states near 160--200~T. At this threshold, the optical transition mechanism undergoes a dramatic shift from an electron-dominated collective mode to a cooperative electron-hole collective excitation. Furthermore, the extreme-field absorption spectra under thulium fiber laser excitation ($\hbarω_0 = 0.636$~eV)---culminating in a massive resonance near 400~T with a shoulder at 200~T---are excellently reproduced by a collective Alfvén wave model. This analysis also evidences a magnetic-field-induced enhancement of the sublattice potential asymmetry parameter (from 0.10~eV to 0.12~eV). This directly signifies that the macroscopic electron-hole band asymmetry is further amplified by the applied magnetic field. Ultimately, the field-induced energy inversion generates a strongly interacting, fully compensated electron-hole plasma. The resonant excitation of Alfvén waves in this regime demonstrates that a pristine tabletop analog to the relativistic electron-positron plasmas found in astrophysical extremes can be elegantly realized within a 2D graphene system.
Comments19 pages, 7 figures
