BUNCHING TRANSITIONS ON VICINAL SURFACES AND QUANTUM N-MERS

We study vicinal crystal surfaces with the terrace-step-kink model on a discrete lattice. Including both a short-ranged attractive interacti on and a long-ranged repulsive interaction arising from elastic forces , we discover a series of phases in which steps coalesce into bunches of n steps each. The value of n varies with temperature and the ratio of short- to long-range interaction strengths. We propose that the bun ch phases have been observed in very recent experiments on Si surfaces . In a mapping of the model to a system of bosons on a 1D lattice, the bunch phases appear as quantum n-mers. [S0031-9007(98)07291-3].