Dynamical properties of the Haldane chain with bond disorder
Jing-Kai Fang , Jun-Han Huang , Han-Qing Wu , Dao-Xin Yao
Front. Phys. ›› 2022, Vol. 17 ›› Issue (3) : 33503
By using Lanczos exact diagonalization and quantum Monte Carlo combined with stochastic analytic continuation, we study the dynamical properties of the S = 1 antiferromagnetic Heisenberg chain with different strengths of bond disorder. In the weak disorder region, we find weakly coupled bonds which can induce additional low-energy excitation below the one-magnon mode. As the disorder increases, the average Haldane gap closes at δ∆ ~ 0.5 with more and more low-energy excitations coming out. After the critical disorder strength δc ~ 1, the system reaches a random-singlet phase with prominent sharp peak at ω = 0 and broad continuum at ω > 0 of the dynamic spin structure factor. In addition, we analyze the distribution of random spin domains and numerically find three kinds of domains hosting effective spin-1/2 quanta or spin-1 sites in between. These “spins” can form the weakly coupled longrange singlets due to quantum fluctuation which contribute to the sharp peak at ω = 0.
Haldane chain / Heisenberg model / magnetic excitation / quantum phase transition / random singlet / disorder / exact diagonalization / quantum Monte Carlo
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Higher Education Press
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