准一维多链无序体系跳跃电导特性

Theoretical study on the hopping conductivity of quasi-one-dimensional disordered systems

在单电子紧束缚近似下,建立了准一维多链无序体系直流、交流电子跳跃输运模型,通过计算探讨了无序模式、维度效应、温度及外场对其直流、交流电导率的影响.计算结果表明:准一维多链无序体系的直流、交流电导率随着格点能量无序度的增大而减小,非对角无序具有增强体系电子输运能力的作用.随着链数的增加,体系的直流、交流电导率增大,但格点能量无序度较小时,维度效应的影响不明显.在对角无序情况下准一维多链无序体系的交流电导率随温度的升高而增大,而在非对角无序模式下却随温度的升高而减小,但对于直流情况,体系的直流电导率随温度的升高而增大.在外加电场的调制下,体系的直流电导率在强场区随电场强度增加而增大得很快,呈现出非欧姆定律特性,但链数越多,体系的直流电导率随外场强度的增加而增大得越平缓.当外加交变电场时,准一维多链无序体系的交流电导率随外场频率的增大而增大,并满足σac(ω)∝ω2[ln(1/ω)]2的关系式.

Based on a tight-binding disordered model describing a single electron band,a model of quasi-one-dimensional disordered systems with several chainsis established,and the direct current（dc） and alternating current（ac） conductance formula are obtained.By calculation,the dependence of the dc and ac conductivity on the disorder mode,dimension,temperature,and electric field is studied.The results indicate that the dc and ac conductivity of the systems decreases with the increase of the degree of lattices energy disorder,while the off-diagonal disorder can enhance the electrical conductivity of the system.Meanwhile,the conductivity increases with the increase of the number of chains in the systems.The model also quantitatively explains the temperature and electric field dependence of the conductivity of the system,that is,in diagonal disordered systems,the ac conductivity of the systems increases with the increasing of temperature,in off-diagonal disordered systems,the ac conductivity of the systems decreases with the increasing of temperature,while the dc conductivity of the systems in all disordered modes increases with the increasing of temperature.In addition,the dc conductivity of the quasi-one-dimensional disordered systems increases with the increasing of the strength of dc electric field,showing the non-Ohm＇s law conductivity characteristics,and the larger the number of chains in systemis,the more slowly the dc conductivity of systems increases with the increasing electric field.The ac conductivity quasi-one-dimensional disordered systems increases as the frequency of the external electric field rises,satisfying the relation σac（ω） ∝ ω2[ln（1/ω）]2.