Ping-pong configurations and circular orders on free groups

We discuss actions of free groups on the circle with ``ping-pong'' dynamics; these are dynamics determined by a finite amount of combinatorial data, analogous to Schottky domains or Markov partitions. Using this, we show that the free group F-n admits an isolated circular order if and only if n is even, in stark contrast with the case for linear orders. This answers a question from [21]. Inspired by work in [2], we also exhibit examples of ``exotic'' isolated points in the space of all circular orders on F-2. Analogous results are obtained for linear orders on the groups F-n x Z.