Band Ordering and Dynamics of Cu2–xTe and Cu1.98Ag0.2Te

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• 作者：Ali A. Sirusi ; Sedat Ballikaya ; Jing-Han Chen ; Ctirad Uher ; Joseph H. Ross Jr.
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：July 14, 2016
• 年：2016
• 卷：120
• 期：27
• 页码：14549-14555
• 全文大小：391K
• 年卷期：0
• ISSN：1932-7455

文摘

⁶³Cu, ⁶⁵Cu, and ¹²⁵Te NMR measurements are reported for Cu_2–xTe and Cu_1.98Ag_0.2Te. 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.