Interband Optical Experiments on Bloch Oscillations: Measurements of the Spatial Dynamics

Abstract

In the previous chapter, we discussed the first interband optical experiments on Bloch oscillations, which clarified the basic phenomena. Although those experiments have brought important insight, they have only offered information about the temporal dynamics of the Bloch oscillations, which is, in principle, only a corollary of the observation of the Wannier-Stark ladder in frequency space.

In this chapter, we discuss more recent experiments which go further. The emphasis is laid on experiments which use a novel experimental technique that allows one to directly measure the spatial displacement of the carriers as a function of time, and thus to investigate the properties of the harmonic motion predicted by Zener (Sect. 4.1). We then discuss experiments which show that the spatial dynamics can be controlled by the choice of optical excitation (Sect. 4.2). The use of the above method for determining spatial dynamics to investigate the influence of scattering and plasmon coupling on the spatial dynamics of the Bloch oscillations is described (Sect. 4.3). In the final section (Sect. 4.4), we show that the harmonic Bloch oscillations are superimposed on a linear motion, which is a coherent analogue of the Shapiro effect in superconductors.