Kukushkin Igor V, Smet Jurgen H, Scarola Vito W, Umansky Vladimir, von Klitzing Klaus
Max Planck Institute for Solid State Research, D-70569 Stuttgart, Germany.
Science. 2009 May 22;324(5930):1044-7. doi: 10.1126/science.1171472. Epub 2009 Apr 30.
The rich correlation physics in two-dimensional (2D) electron systems is governed by the dispersion of its excitations. In the fractional quantum Hall regime, excitations involve fractionally charged quasi particles, which exhibit dispersion minima at large momenta referred to as rotons. These rotons are difficult to access with conventional techniques because of the lack of penetration depth or sample volume. Our method overcomes the limitations of conventional methods and traces the dispersion of excitations across momentum space for buried systems involving small material volume. We used surface acoustic waves, launched across the 2D system, to allow incident radiation to trigger these excitations at large momenta. Optics probed their resonant absorption. Our technique unveils the full dispersion of such excitations of several prominent correlated ground states of the 2D electron system, which has so far been inaccessible for experimentation.
二维电子系统中丰富的关联物理由其激发态的色散决定。在分数量子霍尔 regime 中，激发涉及分数电荷准粒子，这些准粒子在大动量处表现出色散最小值，称为旋子。由于缺乏穿透深度或样品体积，这些旋子很难用传统技术探测到。我们的方法克服了传统方法的局限性，追踪了涉及小材料体积的掩埋系统中激发态在动量空间中的色散。我们利用在二维系统中传播的表面声波，使入射辐射在大动量处触发这些激发。光学方法探测它们的共振吸收。我们的技术揭示了二维电子系统几个突出的关联基态的此类激发态的完整色散，而迄今为止实验上无法获得这些信息。
