Thermal quantum correlations and quantum phase transitions in Ising-XXZ diamond chain

Quantum phase transitions (QPT) in the infinite-long Ising-XXZ diamond chain, characterized by the quantum correlations measured by the quantum discord (QD) and the entanglement of formation (EoF), are investigated exactly by the transfer-matrix method. QD and EoF are calculated numerically for different values of anisotropy parameter, external magnetic field, and temperature. It is found that the singularity of QD and EoF around quantum critical points (QCPs), especially that of their first derivatives may not only spotlight the QCPs but also depict the QPT from unentangled state in ferrimagnetic phase to an entangled state in frustrated phase or to an entangled state in the ferrimagnetic phase.