Thermodynamics around magnetic phase transitions in alternating double-chain spin systems  

作　　者：丁林杰 钟园 樊帅伟 朱丽娅 

机构地区：[1]Department of Physics, China Three Gorges University

出　　处：《Chinese Physics B》2014年第12期435-443,共9页中国物理B（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(Grant Nos.11204157,11174179,and 11247020);the Hubei Provincial Natural Science Foundation,China(Grant No.D20131307);the China Three Gorges University Project(Grant No.KJ2011B068)

摘　　要：The thermodynamics and quantum phase transitions of two typically alternating double-chain systems are investigated by Green＇s function theory.（i） For the completely antiferromagnetic（AFM） alternating double-chain, the low-temperature antiferromagnetism with gapped behavior is observed, which is in accordance with the experimental result. In a magnetic field, we unveil the ground state phase diagram with zero plateau, 1/2 plateau, and polarized ferromagnetic（FM） phases,as a result of the intra-cluster spin-singlet competition. Furthermore, the Gr ¨uneisen ratio is an excellent tool to identify the quantum criticality and testify various quantum phases.（ii） For the antiferromagnetically coupled FM alternating chains,the 1/2 magnetization plateau and double-peak structure of specific heat appear, which are also observed experimentally.Nevertheless, the M–h curve shows an anomalous behavior in an ultra-low field, which is ascribed to the effectively weak Haldane-like state, demonstrated by the two-site entanglement entropy explicitly.The thermodynamics and quantum phase transitions of two typically alternating double-chain systems are investigated by Green＇s function theory.（i） For the completely antiferromagnetic（AFM） alternating double-chain, the low-temperature antiferromagnetism with gapped behavior is observed, which is in accordance with the experimental result. In a magnetic field, we unveil the ground state phase diagram with zero plateau, 1/2 plateau, and polarized ferromagnetic（FM） phases,as a result of the intra-cluster spin-singlet competition. Furthermore, the Gr ¨uneisen ratio is an excellent tool to identify the quantum criticality and testify various quantum phases.（ii） For the antiferromagnetically coupled FM alternating chains,the 1/2 magnetization plateau and double-peak structure of specific heat appear, which are also observed experimentally.Nevertheless, the M–h curve shows an anomalous behavior in an ultra-low field, which is ascribed to the effectively weak Haldane-like state, demonstrated by the two-site entanglement entropy explicitly.

关 键 词：THERMODYNAMICS quantum phase transition double-chain spin system 

分 类 号：O413.1[理学—理论物理]