arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2003.00309cond-mat.str-elcond-mat.supr-con
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CuxBi2Te2Se中可能的格序和电荷序

Possible Lattice and Charge Order in CuxBi2Te2Se

Yanan Li, Nathaniel P. Smith, William Rexhausen, Marvin A Schofield, Prasenjit Guptasarma

摘要:

金属嵌入到层状拓扑绝缘体材料如二元硫属化物Bi 2 X 3(X=Te或Se)中产生了新颖的二维电子气物理、向超导性的相变以及有趣的磁基态。最近感兴趣的是嵌入驱动的晶格畸变,密度波有序,并在附近的不稳定性的嵌入引起的新现象的出现之间的相互作用。在这里,我们研究了Cu插层对三元硫族化合物Bi2Te2Se的影响。本文报道了在Cu_(0.3)Bi_2Te_2Se中发现的室温下的周期性晶格畸变,以及在Td = 220K附近的电荷密度波跃迁。我们还报告,第一次,一个完整的研究的CuxBi2Te2Se系统,和铜插层对晶体结构,声子结构,和电子性质的0.0 $\le$ x $\le$ 0.5的效果。我们的电子衍射研究揭示了强烈的布拉格点在倒易晶格位置禁止ABC堆垛,可能导致堆垛层错,或超晶格。对于0 $\lt$ x $\lt$ 0.2,c轴晶格参数随x单调变化,但对于更高的x急剧下降。类似地,拉曼声子模式$A^2_{1g}$和$E_g$对于0 $\lt$ x $\lt$ 0.2单调软化,但对于x $\gt$ 0.2急剧硬化。这表明Cu可能嵌入高达x $\sim$ 0.2,随后在较高值处发生部分位点取代。所产生的应变使得0.2 $\lt$ x $\lt$ 0.3区域易受不稳定性和扭曲的影响。我们的结果指向存在一个无公度CDW以上Td = 220 K。这项工作加强了普遍认为,插层有助于显着的晶格和电荷自由度的层状硫属化合物的不稳定性。

英文摘要:

Metal intercalation into layered topological insulator materials such as the binary chalcogenide Bi2X3 (X=Te or Se) has yielded novel two-dimensional electron-gas physics, phase transitions to superconductivity, as well as interesting magnetic ground states. Of recent interest is the intercalation-driven interplay between lattice distortions, density wave ordering, and the emergence of new phenomena in the vicinity of instabilities induced by intercalation. Here, we examine the effects of Cu-intercalation on the ternary chalcogenide Bi2Te2Se. We report the discovery, in Cu0.3Bi2Te2Se, of a periodic lattice distortion at room temperature, together with a charge density wave transition around Td = 220K. We also report, for the first time, a complete study of the CuxBi2Te2Se system, and the effect of Cu-intercalation on crystal structure, phonon structure, and electronic properties for 0.0 $\le$ x $\le$ 0.5. Our electron diffraction studies reveal strong Bragg spots at reciprocal lattice positions forbidden by ABC stacking, possibly resulting from stacking faults, or a superlattice. The c-axis lattice parameter varies monotonically with x for 0 $\lt$ x $\lt$ 0.2, but drops precipitously for higher x. Similarly, Raman phonon modes $A^2_{1g}$ and $E_g$ soften monotonically for 0 $\lt$ x $\lt$ 0.2 but harden sharply for x $\gt$ 0.2. This indicates that Cu likely intercalates up to x $\sim$0.2, followed by partial site-substitutions at higher values. The resulting strain makes the 0.2 $\lt$ x $\lt$ 0.3 region susceptible to instabilities and distortions. Our results point toward the presence of an incommensurate CDW above Td = 220 K. This work strengthens prevalent thought that intercalation contributes significantly to instabilities in the lattice and charge degrees of freedom in layered chalcogenides.

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