Perpustakaan Digital ITB

Phase transitions at a finite (i.e., nonzero) temperature are typically dominated by classical correlations, in contrast to zero temperature transitions where quantum mechanics plays an essential role. Therefore, it is natural to ask if there are any signatures of a finite-temperature phase transition in measures that are sensitive only to quantum correlations. Here we study one such measure, namely, entanglement negativity, across finite-temperature phase transitions in several exactly solvable Hamiltonians and find that it is a singular function of temperature across the transition. Our results also lead to a mean-field argument that shows that negativity can distinguish spontaneous symmetry breaking with local order parameter at finite temperature from that in the ground state. Along the way, we prove certain general results which simplify the calculation of negativity for commuting projector Hamiltonians and as an aside, we also calculate the entanglement of formation exactly in an interacting model.