Topological phase transitions of Thouless charge pumping realized in helical organic molecules with long-range hopping
Topological phase transitions of Thouless charge pumping realized in helical organic molecules with long-range hopping
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DOI：
10.1103/physrevb.102.155402
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发表时间：
2020-06
影响因子：
3.7
通讯作者：
Ai-Min Guo;Pei-Jia Hu;Xiao-Hui Gao;Tie-Feng Fang;Qing-feng Sun
中科院分区：
文献类型：
--
作者：
Ai-Min Guo;Pei-Jia Hu;Xiao-Hui Gao;Tie-Feng Fang;Qing-feng Sun
最近的研究表明，螺旋有机分子，如DNA和$\alpha$-螺旋蛋白质，可以表现为无源量子泵时，旋转电场施加垂直于他们的螺旋轴。在这里，我们调查的影响，这种拓扑泵浦电子在单螺旋有机分子的长程跳跃。在衰变指数$\mu$控制的长程跳跃的变化下，我们发现分子能带结构中的能隙在衰变指数的临界值$\mu_c$处关闭，并在偏离$\mu_c$的$\mu$处重新打开。在一个泵浦周期的相关散装带获得不同的陈数在强（$\mu \mu_c$）的长程跳跃制度，在临界突然跳跃。这种拓扑相变也被证明是分开的两个不同的行为的中间带隙端态在泵浦过程中。端态携带由旋转电场泵浦的量子化电流，并且电流通过在差距上扫描费米能量而形成平台。在强跳变阶段，量子化电流平台为正，在弱跳变阶段，量子化电流平台反转为幅度较小的负平台。然而，由于分子的有限尺寸，反转是平滑的交叉，而不是急剧的过渡。我们表明，这些传输特性的拓扑相变也可以观察到在有限的温度。
Recent studies indicated that helical organic molecules, such as DNA and $\alpha$-helical protein, can behave as Thouless quantum pumps when a rotating electric field is applied perpendicularly to their helical axes. Here we investigate the influence of long-range hoppings on this topological pumping of electrons in single-helical organic molecules. Under variation of the long-range hoppings governed by a decay exponent $\mu$, we find an energy gap in the molecular band structure closes at a critical value $\mu_c$ of the decay exponent and reopens for $\mu$ deviating from $\mu_c$. The relevant bulk bands in a pumping cycle acquire different Chern numbers in the strong ($\mu \mu_c$) long-range hopping regimes, with a sudden jump at criticality. This topological phase transition is also shown to separate two distinct behaviors of the midgap end states in the pumping process. The end states carry quantized current pumped by the rotating electric field and the current forms a plateau by sweeping the Fermi energy over the gap. In the strong hopping phase, the quantized current plateau is positive, which is reversed to a negative one with smaller amplitude in the weak hopping phase. However, the reversal is a smooth crossover, not a sharp transition, due to the finite sizes of the molecules. We show that these transport characteristics of the topological phase transition could also be observed at finite temperatures.