Quantum phase transition in dimerised spin-1/2 chains
Quantum phase transition in dimerised antiferromagnetic Heisenberg spin chain has been studied. A staircase structure in the variation of concurrence within strongly coupled pairs with that of external magnetic field has been observed indicating multiple critical (or critical like) points. Emergence of entanglement due to external magnetic field or magnetic entanglement is observed for weakly coupled spin pairs too in the same dimer chain. Though closed dimerised isotropic XXX Heisenberg chains with different dimer strengths were mainly explored, analogous studies on open chains as well as closed anisotropic (XX interaction) chains with tilted external magnetic field have also been studied.
KeywordsQuantum phase transition Concurrence Dimerised Heisenberg chain
AD and SB acknowledge the support offered by Acharya Prafulla Chandra College and Sarojini Naidu College for Women for carrying out this work, part of which was done as part of their project work at Master’s level under supervision of SS. The authors acknowledge some helpful discussions with Jacques H.H. Perk regarding the earlier studies on phase transitions in alternating chains and finite size effects of the spin chains, during the preparation of the final version of this manuscript, in which authors were made aware of some old references too. The authors also like to acknowledge Edward Fel’dman for drawing their attention to some recent works. The anonymous reviewers are also being acknowledged for their useful suggestions and for pointing out some useful references. The work of SS was supported by the UGC MRP Grant (Sanction No. F. PSW-164/13-14). SS further acknowledges the technical supports she got from Dr. Sankhasubhra Nag, SNCW, Kolkata.
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