Bi$_2$Se$_3$中140 K电子转变的异常现象：可能的电荷有序在缺陷工程化系统中
Anomalous 140 K electronic transition in Bi$_2$Se$_3$: Possible charge order in a defect-engineered system
AI总结：
本研究发现Bi$_2$Se$_3$中140 K异常电子转变与电荷有序有关，通过电子衍射和NMR证实了能量隙的开启，揭示了本征缺陷对拓扑材料中电荷有序与超导体相互作用的影响。
摘要：
我们报道了在高质量Bi$_2$Se$_3$中发现的140 K异常电子转变，其中在缺陷调节系统中出现了电荷有序。本征缺陷（Se空位和Bi掺杂）——我们的可重复生长方法固有特性——调节电子态而不影响样品完整性，与掺杂诱导相在相关拓扑材料中相似。Bi$_2$Se$_3$及相关化合物（如Bi$_2$Te$_3$）的六边形变形费米面和强折叠长期以来表明了密度波有序的可能性，最近在超导Cu和Nb掺杂的Bi$_2$Se$_3$中的研究进一步突显了电荷有序在非常规超导体中的作用。在此，我们通过电子衍射发现了一个接近室温的周期性晶格畸变，与弥散电荷有序一致。这伴随着140 K电子转变，表现为电阻率测量中的明显异常，呈现出半导体样的上升趋势，标志着能量隙的开启。核磁共振（NMR）研究了$^{209}$Bi自旋晶格弛豫率（1/$T_1$）揭示了一个同时发生的转变，证实了8 meV能量隙的出现。我们的结果与Bi$_2$Se$_3$中缺陷稳定电荷有序一致，将本征缺陷与它的电子性质联系起来，并提供了更广泛的见解，揭示了拓扑材料中电荷有序与超导体相互作用的更广泛图景。
英文摘要：
We report an anomalous electronic transition at 140~K in high-quality Bi$_2$Se$_3$, where charge order emerges in a defect-tuned system. Native defects (Se vacancies and Bi intercalation)-intrinsic to our reproducible growth method-modulate electronic states without compromising sample integrity, mirroring doping-induced phases in correlated topological materials. The hexagonally deformed Fermi surfaces and strong nesting in Bi$_2$Se$_3$ and related compounds (such as, Bi$_2$Te$_3$ ) have long suggested the possibility of density wave ordering, with recent work on superconducting Cu- and Nb-doped Bi$_2$Se$_3$ further highlighting charge order's role in unconventional superconductivity. Here, we identify a periodic lattice distortion near room temperature via electron diffraction, consistent with diffuse charge order. This is accompanied by a 140~K electronic transition, manifested in resistivity measurements as a pronounced anomaly, exhibiting a semiconductor-like upturn, signaling the opening of an energy gap. Nuclear magnetic resonance (NMR) studies of the $^{209}$Bi spin-lattice relaxation rate (1/$T_1$ ) reveal a concurrent transition, confirming the emergence of an 8~meV energy gap. Our results are consistent with defect-stabilized charge order in Bi$_2$Se$_3$ , linking native defects to its electronic properties and offering broader insights into the interplay between charge order and superconductivity in topological materials.
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