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arXiv 2501.08991cond-mat.mes-hall
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具有一般边界条件的 PT 对称扩展 Su-Schrieffer-Heeger 模型中的边缘态与持续电流

Edge states and persistent current in a PT-symmetric extended Su-Schrieffer-Heeger model with generic boundary conditions

Supriyo Ghosh, Pijush K. Ghosh, Shreekantha Sil

AI总结:

该研究构建含 NNN、BLG 和磁场的 PT 对称扩展 SSH 模型,在 GBC 下解析与数值分析能带、边缘态及持续电流,揭示拓扑相、BBC 与 NHSE。

摘要:

我们考虑 Su-Schrieffer-Heeger(SSH)模型的一种推广:纳入次近邻(NNN)相互作用和平衡损耗-增益(BLG),并使整个系统受到外部均匀磁场。我们在一般边界条件(GBC)下研究该扩展 SSH 模型的能带结构、边缘态和持续电流,其中周期、反周期和开放边界条件均作为特殊情形出现。结果表明,点带隙随 NNN 相互作用强度增大而减小,并在超过临界值后消失。此外,在周期边界条件(PBC)下,对于非零 NNN 相互作用,线隙呈现类闭环结构。在 PBC 下,Zak 相不受 NNN 相互作用贡献。我们证明,在 PBC 情形下,NNN 相互作用对半填充极限中的持续电流没有影响。我们证明,对于一类 GBC,不含 NNN 相互作用的模型可以精确求解,其中 PBC、反周期边界条件(APBC)和反厄米边界条件(AHBC)作为特殊情形出现。对于 NNN 相互作用为零的情况,我们得到了开放边界条件(OBC)和 AHBC 下边缘态的解析表达式。对于 OBC,我们通过数值计算表明,在 PBC 下 PT 对称性破缺的参数区域内,非零 NNN 相互作用会使拓扑平庸相中出现边缘态。在拓扑非平庸相中,OBC 下的边缘态仅在 NNN 强度达到某个临界值之前存在,并在超过临界值后消失。未破缺 PT 相的体-边对应(BBC)与厄米 SSH 模型相似,而在破缺 PT 相中可观察到非厄米趋肤效应(NHSE)。

英文摘要:

We consider a generalization of the Su-Schrieffer-Heeger(SSH) model by including next-nearest neighbour(NNN) interaction and balanced loss-gain(BLG), and subjecting the whole system to an external uniform magnetic field. We study the band structure, edge states and persistent current in this extended SSH model under General Boundary Condition(GBC) of which the periodic, anti-periodic and open boundary conditions appear as special cases. It is shown that the point bandgap decreases with the increasing value of the strength of the NNN interaction and vanish beyond a critical value. Further, the line gap exhibits closed-loop like structures for non-vanishing NNN interaction under the Periodic Boundary Condition(PBC). The Zak phase receives no contribution from the NNN interaction under the PBC. We show that the NNN interaction has no effect on the persistent current in the half-filled limit for the case of PBC. We show that the model without the NNN interaction is exactly solvable for a class of GBC of which PBC, anti-periodic boundary condition(APBC) and anti-hermitian boundary condition(AHBC) arise as special cases. We obtain analytic expressions for the edge states in the case of Open Boundary Condition(OBC) and AHBC for vanishing NNN interaction. We show numerically for OBC that edge states in the topologically trivial phase appear for non-vanishing NNN interaction in the parametric regions where PT-symmetry is broken under PBC. In the topologically non-trivial phase, the edge states under OBC exists only up to a critical value of the NNN strength and vanishes beyond a critical value. The bulk-boundary correspondence(BBC) for unbroken PT-phase is similar to hermitian SSH model, while non-Hermitian skin effect(NHSE) is observed for broken PT-phase.

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