We employ first-principles calculations to investigate the Topological States (TS) and Thermoelectric (TE) transport properties of three dimensional (3D) Gold Iodide (AuI) which belongs to the zincblende family. We explore, Semi-Metal (SM) to Topological Conductor (TC) and Topological Insulator (TI) phase transitions. Under pristine conditions, AuI exhibits Dirac SM nature but, under the influence of mild isotropic compressive pressure the system undergoes electronic quantum phase transition driving it into non-trivial topological state. This state exhibits Dresselhaus like band spin splitting leading to a TC state. In order to realize TI state from the SM state, we break the cubic symmetry of the system by introducing a compressive pressure along (001) crystal direction. The non-trivial TI nature of the system is characterized by the emergence of robust surface states and the Z2invariant ν0= 1 which indicates a strong TI nature. A novel facet of the phase transition discussed here is, the -s and -p,-d orbital band inversion mechanism which is unconventional as compared to previously explored TI families. This mechanism unravels new path by which TI materials can be predicted. Also, we investigated the lattice and electronic contributions to the TE transport properties. We characterize the TE performance by calculating the Figure of Merit (zT) and find that, at room temperature (300 K) and for a fixed doping concentration (i.e., n = 1×1019cm-3) the zT is 0.55 and 0.53 for electrons and holes respectively. This is quite remarkable since, higher values of zT are generally predicted at higher temperature scales whereas, zT values as in the present case are desired at room temperatures for various energy applications. The manifestation of nontrivial TS governed by the unconventional band inversion mechanism and the TE properties of AuI make it a unique multi-functional candidate with probable thermoelectric and spintronic applications.

中文翻译：

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闪锌矿碘化金拓扑绝缘体中-s,-pd能带反转的出现及其热电性能

我们采用第一性原理计算来研究属于闪锌矿家族的三维 (3D) 碘化金 (AuI) 的拓扑态 (TS) 和热电 (TE) 输运特性。我们探索半金属 (SM) 到拓扑导体 (TC) 和拓扑绝缘体 (TI) 的相变。在原始条件下，AuI 表现出狄拉克 SM 性质，但在温和各向同性压缩压力的影响下，系统经历电子量子相变，驱动其进入非平凡的拓扑状态。该状态表现出类似 Dresselhaus 的能带自旋分裂，导致 TC 状态。为了从SM态实现TI态，我们通过沿(001)晶向引入压缩压力来打破系统的立方对称性。系统的非平凡 TI 性质的特征是鲁棒表面态的出现和 Z2 不变 ν0= 1，这表明了很强的 TI 性质。这里讨论的相变的一个新颖方面是 -s 和 -p,-d 轨道带反转机制，与之前探索的 TI 系列相比，这是非常规的。这种机制开辟了预测 TI 材料的新途径。此外，我们还研究了晶格和电子对 TE 传输特性的贡献。我们通过计算品质因数 (zT) 来表征 TE 性能，发现在室温 (300 K) 和固定掺杂浓度（即 n = 1×1019cm-3）下，电子的 zT 分别为 0.55 和 0.53和孔分别。这是非常显着的，因为通常在较高的温度范围下预测较高的 zT 值，而对于各种能源应用，在室温下需要在当前情况下的 zT 值。由非常规能带反转机制控制的非平凡 TS 的表现和 AuI 的 TE 特性使其成为具有可能的热电和自旋电子应用的独特多功能候选者。