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电子强关联效应使得过渡金属硫化物1T-TaS2在低温时为Mott绝缘体，而层间堆叠错位及杂质又会引入相当强的无序效应.利用统计动力学平均场理论数值方法研究了无序效应对Mott绝缘相的影响，发现非对角跃迁无序和对角无序效应均不会引起从绝缘体到金属的相变.杂质引入的对角无序达到一定强度后Mott能隙会完全闭合，而堆叠错位引入的非对角跃迁无序不论多强都无法关闭Mott能隙.在半满情况，非对角无序会导致上下Hubard带对称地分别出现一个奇异态，而通过晶格尺寸标度研究证明了这种反常的电子态仍然是Anderson局域态.
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关键词:
- 动力学平均场理论 /
- Mott绝缘相 /
- Anderson局域化 /
- 非对角跃迁无序
In the layered dichalcogenide 1T-TaS2, whether there is a disorder-driven transition from insulator to metal is still a matter in dispute. It is predicted that the commensurate charge density wave (CCDW) phase at low temperature behaves as a Mott insulator due to the strong correlation of electrons. Meanwhile, the stacking of TaS layers is found to be dislocated along the c axis, which will introduce considerable effect of disorder. Therefore, further theoretical study is needed to show the cooperative effect of correlation and disorder in 1T-TaS2. The statistical dynamical mean-field theory, which treats interactions and disorder on an equal footing, is used to study the effect of disorder on the Mott insulating phase in 1T-TaS2. Two different kinds of disorder effects are considered in the one-dimensional extended Anderson-Hubbard model, where the stacking dislocation of TaS layers is described by the off-diagonal hopping disorder and the diagonal disorder term represents the effect of disorder introduced by impurities. We find that the off-diagonal disorder by itself could not close the Mott gap at Fermi level, suggesting that Mott mechanism should be more dominant in the CCDW phase of 1T-TaS2 with the stacking dislocation of TaS layers. On the other hand, the diagonal disorder introduced by impurities will close the Mott gap when the strength of disorder (W) is larger than the correlation of electrons (U). Proved by the lattice-size scaling of the generalized inverse participation ratio, both the off-diagonal disorder and diagonal disorder can make all states Anderson-localized. As a result, there is no disorder-induced metal-insulator transition in a correlated system with either off-diagonal disorder or diagonal disorder. In addition, an anomalistic state is introduced by the off-diagonal disorder at the center of the energy band of the non-interacting system, which is a special Anderson-localized state with a very larger localization length. In the correlated cases, the electron-electron interactions have strong effect on splitting the anomalistic state into two individual states, which are located symmetrically in both the upper and lower Hubbard subbands with an energy interval U.-
Keywords:
- dynamical mean-field theory /
- Mott insulating phase /
- Anderson localization /
- off-diagonal disorder
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[1] Phillips P 2010Rev.Mod.Phys. 82 1719
[2] Lee P A, Ramekrishnan T V 1985Rev.Mod.Phys. 57 287
[3] Abrahams E 201050 Years of Anderson Localization(Singapore:World Scientific Publishing)
[4] Lahoud E, Meetei O N, Chaska K B, Kanigel A, Trivedi N 2014Phys.Rev.Lett. 112 206402
[5] Fazekas P, Tosatti E 1980Physica B 99 183
[6] Sato H, Arita M, Utsumi Y, Mukaegawa Y, Sasaki M, Ohnishi A, Kitaura M, Namatame H, Taniguchi M 2014Phys.Rev.B 89 155137
[7] Bayliss S C, Clark A, Liang W Y 1983J.Phys.C:Solid State Phys. 16 L831
[8] Wilson J A, Di Salvo F J, Mahajan S 2001Adv.Phys. 50 1171
[9] Wilson J A, Di Salvo F J, Mahajan S 1975Adv.Phys. 24 117
[10] Fung K, Steeds J, Eades J 1980Physica B+C 99 47
[11] Song Y, Wortis R, Atkinson W A 2008Phys.Rev.B 77 054202
[12] Claessen R, Burandt B, Carstensen H, Skibowski M 1990Phys.Rev.B 41 8270
[13] Rossnagel K, Smith N V 2006Phys.Rev.B 73 073106
[14] Smith N V, Kevan S D, DiSalvo F J 1985J.Phys.C:Solid State Phys. 18 3175
[15] Georges A, Kotliar G, Krauth W, Rozenberg M J 1996Rev.Mod.Phys. 68 13
[16] Song Y, Atkinson W A, Wortis R 2007Phys.Rev.B 76 045105
[17] Theodorou G, Cohen M H 1976Phys.Rev.B 13 4597
[18] Eggarter T P, Riedinger R 1978Phys.Rev.B 18 569
[19] Fleishman L, Licciardello D C 1977J.Phys.C:Solid State Phys. 10 L125
[20] Soukoulis C M, Economou E N 1981Phys.Rev.B 24 5698
[21] Thouless D J 1972J.Phys.C 5 77
[22] Sun J, He L, Zhao Y Y, Song Y 2016Sci.China:Phys.Mech.Astron. 59 617401
[23] He L, Song Y 2013Acta Phys.Sin. 62 057303(in Chinese)[何龙, 宋筠2013物理学报62 057303]
[24] Lazar P, Martincova J, Otyepka M 2015Phys.Rev.B 92 224104
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