EXPERIMENTAL REALIZATION OF MODE-LOCKING DURING INTRINSIC QUASI-PERIODICITY IN P-TYPE GERMANIUM

During low-temperature impact-ionization breakdown in extrinsic german ium, quasiperiodic current oscillations arise spontaneously. If the tw o competing frequencies (strictly speaking, the corresponding oscillat ory components) can be localized in two spatially separated regions of the sample, mode locking can hardly be observed. However, if the two frequencies can be detected all over the sample, the frequency ratio u ndergoes an exemplary mode-locking sequence under variation of a trans verse magnetic field. We find that the mode lockings are in accordance with the Farey-tree configuration, originally predicted to hold for p eriodically driven systems.