Relation between two measures of entanglement in spin-1/2 and spinless fermion quantum chain systems

The concepts of concurrence and mode concurrence are the measures of entanglement for spin-1/2 and spinless fermion systems, respectively. Based on the Jordan-Wigner transformation, any spin-1/2 system is always associated with a fermion system (called the counterpart system). A comparison of concurrence and mode concurrence can be made with the aid of Marshall's sign rule for the ground states of spin-1/2 XXZ and spinless fermion chain systems. We observe that there exists an inequality between concurrence and mode concurrence for the ground states of the two corresponding systems. The spin-1/2 XY chain system and its spinless fermion counterpart as a realistic example are discussed to demonstrate the analytical results.