Erik Sorensen (McMaster U.)
Novel phases of Kitaev Chains and Ladders

Today, there is a growing class of magnetic materials where it is believed that the interactions are bond-dependent in a way first imagined by Alexei Kitaev thereby opening a way for realizing topological phases. Bond-dependent interactions are strongly frustrating for the system and hinders conventional ordering. However, in these Kitaev materials other interactions are also often present,
among them the well known Heisenberg coupling and also off-diagonal Gamma terms giving rise to an exceptionally rich phase diagram. Even for the simplest models of Kitaev materials it is extremely difficult to arrive at a precise understanding of this complex phase-diagram. Hence, in order to obtain accurate results it is often useful to restrict the analysis to low-dimensions and here we mainly discuss chains and two (and more) leg ladders. Using numerical techniques, it is possible for such models to determine the phase-diagram with very high precision, including the effects of an applied magnetic field. An astonishing abundance of phases arises from the combination of frustration and applied field. In this talk I will focus on some of these phases that appear disordered, without any conventional local magnetic ordering, but where a hidden string-order can be identified.