Study On Quantum Entanglement And Correlation In Mixed-Spin Ising-XXZ Model

Spin systems exhibit rich and unique entanglement and correlation properties,which have always been a hot topic in the field of quantum mechanics,condensed matter physics and quantum information.Quantum entanglement,mutual information and coherence,as important resources of quantum information theory,have attracted extensive attention.Currently,most research is focused on one-dimensional spin systems,with relatively few studies on quasi-one-dimensional spin systems.In this paper,we study the quantum coherence and mutual information in the quasi-onedimensional mixed spin(1/2,5/2)Ising-XXZ model and the quantum entanglement in the quasi one dimensional mixed spin(1/2,s)Ising-XXZ model.The main content is summarized as follows:1.The quantum coherence and mutual information of mixed spin(1/2,5/2)Ising-XXZ model are calculated by transfer matrix method,and the effects of Ising interaction,temperature and magnetic field on them are discussed.The results show that the quantum coherence decreases gradually with increasing Ising interaction at extremely low temperatures,while there are a minimum of mutual information in isotropic systems and four minima in anisotropic systems.Furthermore,quantum coherence and mutual information jump abruptly at quantum phase transition points where the first derivatives of them exhibit singular behaviors.The quantum coherence and mutual information at finite temperatures are also studied.As the temperature increases,they decrease monotonously at weak magnetic field and increase firstly and then decrease at higher one,which caused by the competition between thermal fluctuation and magnetic field.Compared with quantum mutual information,quantum coherence exists over a wider range of magnetic field and temperature,which can be easily manipulated experimentally.2.The quantum entanglement of mixed-spin(1/2,s)Ising-XXZ model is studied by transfer matrix method,and the influences of spin quantum numbers,external magnetic field,temperature,anisotropy parameter,and interaction coupling constants on quantum entanglement are discussed.The results reveal that as the spin quantum number increases,the system’s critical magnetic field and critical temperature also grow,and both temperature and external magnetic field suppress entanglement in Heisenberg dimers.At finite temperatures,for smaller spin quantum numbers(s = 1/2,1),quantum entanglement monotonically decreases with increasing external magnetic field,while for larger spin quantum numbers(s = 3/2,2,5/2),quantum entanglement in itially increases and then decreases as the external magnetic field changes.In the extre mely low-temperature regime,for different spin quantum numbers,quantum entanglem ent undergoes abrupt changes at the critical magnetic field,with larger spin quantum numbers yielding higher critical magnetic field values.In the absence of an external magnetic field,integer and half-integer spin systems reach different stable entanglemen t values as the anisotropy parameter changes,with half-integer spin systems attaining larger stable values than integer spin systems.When an external magnetic field is prese nt,entanglement undergoes abrupt changes at the critical anisotropy parameter values,with smaller spin quantum number systems exhibiting larger anisotropy parameter values for the abrupt changes.