Finite temperature detection of quantum critical points: a comparative study

We comparatively study three of the most useful quantum information tools to detect quantum critical points (QCPs) when only finite temperature data are available. We investigate quantitatively how the quantum discord, the quantum teleportation based QCP detectors, and the quantum coherence spectrum pinpoint the QCPs of several spin-$1/2$ chains. We work in the thermodynamic limit (infinite number of spins) and with the spin chains in equilibrium with a thermal reservoir at temperature $T$. The models here studied are the $XXZ$ model with and without an external longitudinal magnetic field, the Ising transverse model, and the $XY$ model subjected to an external transverse magnetic field.
Comment: 16 pages, 16 figures, RevTex4, published version