Band Ordering and Dynamics of Cu2–xTe and Cu1.98Ag0.2Te
Band Ordering and Dynamics of Cu2–xTe and Cu1.98Ag0.2Te
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DOI：
10.1021/acs.jpcc.6b04785
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发表时间：
2016-07
影响因子：
3.7
通讯作者：
A. Sirusi;S. Ballikaya;J. Chen;C. Uher;J. H. Ross
中科院分区：
文献类型：
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作者：
A. Sirusi;S. Ballikaya;J. Chen;C. Uher;J. H. Ross
报道了Cu2-xTe和Cu1.98Ag0.2Te的~(63)Cu、~(65)Cu和~(125)Te的核磁共振测量结果。结果表明，铜离子的跃迁开始于室温以下，包括与高温输运测量一致的活化行为，但随着银的取代，跃迁势垒显著增强。我们还通过结合核磁共振线形和弛豫测量分离了Korringa行为，从而确定了两个核的大的负化学位移，以及价带中大的铜和Te的S态贡献。通过热容测量和密度泛函方法计算的化学位移得到了进一步的比较。较大的抗磁化学位移与先前发现的具有拓扑非平凡带反转的材料的行为相吻合，此外，较大的金属位移表明态的价带密度具有类似的特征，这表明Cu2Te可能具有类似的反转特征。
63Cu, 65Cu, and 125Te NMR measurements are reported for Cu2–xTe and Cu1.98Ag0.2Te. The results demonstrate an onset of Cu-ion hopping below room temperature, including an activation behavior consistent with high-temperature transport measurements but with a significant enhancement of the hopping barriers with Ag substitution. We also separated the Korringa behavior by combining NMR line shape and relaxation measurements, thereby identifying large negative chemical shifts for both nuclei, as well as large Cu and Te s-state contributions in the valence band. Further comparison was obtained through heat capacity measurements and chemical shifts computed by density functional methods. The large diamagnetic chemical shifts coincide with behavior previously identified for materials with topologically nontrivial band inversion, and in addition, the large metallic shifts point to analogous features in the valence band density of states, suggesting that Cu2Te may have similar inverted features.