Two-dimensional open-orbit edge states: A new type of quantum oscillation

Although Landau quantization is absent in the interior of open-orbit metals, electron orbits near sample edges require quantized areas. The edge orbits have very small effective masses and hence can produce anomalously large oscillations in magnetization and matnetoresistance. The quantized edge states are largely independent of the magnetic-field–induced spin-density-wave transitions which occur in two-dimensional open-orbit metals. We propose that these edge states are responsible for the anomalous Schubnikov–de Haas and de Haas–van Alphen oscillations observed in the organic tetramethyltetraselenafulvalene salts conductors (TMTSF${)}_2$X.