1304.0607 (Uma Divakaran)

The three site interacting spin chain in staggered field: Fidelity vs
Loschmidt echo    [PDF]

Uma Divakaran

We study the fidelity and Loschmidt echo of a three site interacting XX chain in presence of staggered field which consists of special types of quantum phase transition points due to change in the topology of the Fermi surface, apart from normal phase transition points from gapped to gapless phases. We focus on the effect of such types of phase transition points on the fidelity, which is the static part of the problem, and Loschmidt echo of this spin chain. We find that on one hand, fidelity is able to detect only the boundaries of the gapped to gapless phase transition and not the phase transition from two Fermi points to four Fermi points which lie within this gapless region. On the other hand, Loschmidt echo is just able to detect one special point in the entire phase diagram. We present the arguments for such a behavior.

View original: http://arxiv.org/abs/1304.0607