Spatial and Temporal Structure of Chaotic Instabilities in an Electron-Hole Plasma in Ge

Abstract

Helical instabilities in an electron-hole plasma in Ge in parallel dc electric and magnetic fields are known to exhibit chaotic behavior. By fabricating probe contacts along the length of a Ge crystal we study the spatial structure of these instabilities, finding two types: (i) spatially coherent and temporally chaotic helical density waves characterized by strange attractors of fractal dimension $d\sim 3$, and (ii) beyond the onset of spatial incoherence, instabilities of indeterminately large fractal dimension $d>\mathrm{}8\mathrm{}$. A transition between these two types of behavior is observed as the applied fields are increased.