Ye Zefang, Frazer Travis D, Cui Haoran, Jia Xun, He Feng, Ma Tengfei, March Stephen, Bank Seth R, Harmon Katherine J, Zhang Zhan, Ravnik Jan, Sander Mathias, Deng Yunpei, Mankowsky Roman, Lemke Henrik, Wen Haidan, Hruszkewycz Stephan O, Gerber Simon, Wang Yan, Wang Yaguo, Cao Yue
Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, 78712, USA.
Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA.
Nat Commun. 2025 Sep 26;16(1):8436. doi: 10.1038/s41467-025-62817-4.
Flatbands, characterized by their dispersionless energy levels in electronic, magnetic, and phononic systems, hold substantial potential for advancements in electronics and quantum information processing. Most flatbands exist in thermal equilibrium and cannot be easily created or annihilated externally, limiting their flexibility as switchable knobs for use in microelectronics and quantum applications. In our work, we demonstrate the generation of a coherent phonon flatband in a GaAs/AlAs superlattice using 800 nm femtosecond laser pulses. This coherent phonon flatband does not correspond to a phonon eigenmode at equilibrium and exhibits strong coupling with two branches of coherently excited longitudinal phonon modes. With molecular dynamics simulations, we show more generally that the coherent phonon flatband can be induced by coherently and spatially modulated optical excitations of superlattice structures. Our results highlight a pathway for coherent phonon flatband creation in the time domain that can be generalized to various superlattice systems, potentially inspiring the realization of coherent flatband generation of other quasiparticles.
平带在电子、磁和声学系统中表现为无色散能级，在电子学和量子信息处理领域具有巨大的发展潜力。大多数平带处于热平衡状态，难以通过外部手段轻易产生或消除，这限制了它们作为微电子和量子应用中可切换旋钮的灵活性。在我们的工作中，我们展示了利用800纳米飞秒激光脉冲在砷化镓/砷化铝超晶格中产生相干声子平带。这种相干声子平带在平衡态下并不对应于声子本征模，并且与两个相干激发的纵向声子模分支表现出强耦合。通过分子动力学模拟，我们更普遍地表明，相干声子平带可以由超晶格结构的相干和空间调制光学激发诱导产生。我们的结果突出了一种在时域中创建相干声子平带的途径，该途径可推广到各种超晶格系统，有望推动其他准粒子相干平带产生的实现。
