Quantum disorder and Griffiths singularities in bond-diluted two-dimensional Heisenberg antiferromagnets
Quantum disorder and Griffiths singularities in bond-diluted two-dimensional Heisenberg antiferromagnets
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键稀释二维海森堡反铁磁体中的量子无序和格里菲斯奇点
DOI：
10.1103/physrevb.73.064406
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
S. Haas
中科院分区：
文献类型：
--
作者：
R. Yu;T. Roscilde;S. Haas
研究了非均匀键稀释正方晶格上自旋为1/2的海森堡反铁磁体的量子相变。结果表明，量子涨落可以通过非均匀的键稀释连续调谐，最终导致长程磁有序的破坏。确定了两个多临界点，在该点处，磁过渡从渗流过渡分离，引入了一种新的量子相变。超过这些多临界点的量子无序相出现，其特征是一个无限的短程反铁磁有序的团簇。在这个阶段，低温均匀磁化率代数发散与非普适指数。这是一个签名，新的量子无序相是一个量子格里菲斯相，也直接证实了局部间隙的统计分布。因此，这项研究提供了一个真正的量子格里菲斯现象在二维海森堡反铁磁体的证据。
We investigate quantum phase transitions in the spin-1/2 Heisenberg antiferromagnet on square lattices with inhomogeneous bond dilution. It is shown that quantum fluctuations can be continuously tuned by inhomogeneous bond dilution, eventually leading to the destruction of long-range magnetic order on the percolating cluster. Two multicritical points are identified at which the magnetic transition separates from the percolation transition, introducing a novel quantum phase transition. Beyond these multicritical points a quantum-disordered phase appears, characterized by an infinite percolating cluster with short ranged antiferromagnetic order. In this phase, the low-temperature uniform susceptibility diverges algebraically with non-universal exponents. This is a signature that the novel quantum-disordered phase is a quantum Griffiths phase, as also directly confirmed by the statistical distribution of local gaps. This study thus presents evidence of a genuine quantum Griffiths phenomenon in a two-dimensional Heisenberg antiferromagnet.