Anomalously enhanced plasma diffusion transverse to a magnetic field in n-Ge

From the broadening of a narrow plasma sheet drifting along E_x × B, we measured the transverse diffusion coefficient D_⊥ in n-Ge. Contrary to the classical theory, D_⊥ increases with the electric field E_x, increases with the magnetic field B up to μ⁺B ≈ 1, and decreases proportional to $\text{1}\text{B}$ in higher magnetic fields. The transverse drift velocity v_⊥ measured simultaneously shows a classical behavior over the whole field ranges of E_x = 3–110 $\text{V}\text{cm}$ and B = 0.1–2.3T, which were used in our experiment.The results correspond to those gained previously in n-InSb13,14]. However, whereas in InSb plasma instabilities were observed together with the anomalous diffusion, no instabilities could be found in Ge. Various ways to arrive at an explanation of the anomalous effect are discussed and possible applications are indicated.