kagome晶格中无序和自旋交换作用对量子霍尔电导率的影响

Influence of disorder and spin exchange interaction on quantum Hall conductivity in kagome lattice

数值计算了kagome晶格中无序和海森堡交换相互作用下的量子霍尔效应,其中无序包括非磁性杂质和磁性杂质,相互作用包括近邻的铁磁和反铁磁海森堡交换相互作用.计算结果表明,非磁性和磁性无序增强将导致量子化的霍尔电导平台从高朗道能级到低朗道能级逐步被破坏.除了破坏霍尔电导平台,磁性杂质还可以解除自旋简并,使系统发生从非常规量子霍尔效应到常规量子霍尔效应的转变.对于自旋交换作用影响下的霍尔电导,铁磁相互作用同样会使系统发生从非常规量子霍尔效应到常规量子霍尔效应的转变,而反铁磁相互作用却对系统的量子霍尔电导没有影响.这暗示着在S=1/2的反铁磁kagome体系中形成的量子自旋液体仍然保有零能隙的特征.

The quantum Hall effect under the disorder and Heisenberg exchange interaction in kagome lattices are numerically calculated.The disorder includes non-magnetic impurities and magnetic impurities,and the interaction contains the nearby ferromagnetic and antiferromagnetic Heisenberg exchange interactions.The calculated results show that the enhancement of non-magnetic and magnetic disorder will cause the quantized Hall conductance platform to be gradually destroyed from the high Landau energy level to the low Landau energy level.Except for destroying the Hall conductivity platform,magnetic impurities can also lift spin degeneration,causing the system to undergo a transition from an unconventional quantum Hall effect to a conventional one.For the Hall conductance under the influence of Heisenberg spin exchange interactions,the ferromagnetic interaction will also trigger the system to undergo a transition from unconventional quantum Hall effect to conventional one,while antiferromagnetic interaction has no effect on the quantum Hall conductivity.This implies that the quantum spin liquid formed in the S=1/2 antiferromagnetic kagome system still retains the characteristic of zero energy gap.