Showing papers by "Uma Divakaran published in 2013"

Three-site interacting spin chain in a staggered field: fidelity versus Loschmidt echo.

Abstract: We study the the ground state fidelity and the ground state Loschmidt echo of a three-site interacting XX chain in presence of a staggered field which exhibits special types of quantum phase transitions due to change in the topology of the Fermi surface, apart from quantum phase transitions from gapped to gapless phases. We find that, on one hand, the fidelity is able to detect only the boundaries separating the gapped from the gapless phase; it is completely insensitive to the phase transition from the two Fermi points region to the four Fermi points region lying within this gapless phase. On the other hand, the Loschmidt echo shows a dip only at a special point in the entire phase diagram and hence fails to detect any quantum phase transition associated with the present model. We provide appropriate arguments in support of this anomalous behavior.

Fidelity susceptibility and Loschmidt echo for generic paths in a three spin interacting transverse Ising model

Abstract: We study the effect of presence of different types of critical points such as ordinary critical point, multicritical point and quasicritical point along different paths on the Fidelity susceptibility and Loschmidt echo of a three spin interacting transverse Ising chain using a method which does not involve the language of tensors. We find that the scaling of fidelity susceptibility and Loschmidt echo with the system size at these special critical points of the model studied, is in agreement with the known results, thus supporting our method.