Weak anti-localization in ultrathin Sb(111) films

We report the first studies of localization in ultrathin Sb films. Sb is a topological semi-metal with a negative bandgap of 180meV, however it is anticipated that in ultra-thin films, quantum confinement will open the bulk gap, such that transport is dominated by the topological surface states. We have studied the magneto-transport of ~nominally 4.5nm thick films of Sb(111) grown via molecular beam epitaxy at a temperature of 300C on nearly lattice matched epilayers. The longitudinal resistance shows positive magneto-resistance, well described by the standard weak anti-localization (WAL) theory of Hikami, Larkin and Nagaoka. The WAL response is consistent with that of a single conducting channel with a phase breaking length of $\sim$200nm at 1.8K. Scanning electron microscopy shows that the Sb growth proceeded by a Volmer-Weber (islanding) process resulting in disordered films. More recent growths performed at lower temperature have yielded significantly less resistive, smoother and thinner films for which transport measurements are ongoing.