Sihi Antik, Pandey Sudhir K
School of Basic Sciences, Indian Institute of Technology Mandi, Kamand 175075, India.
School of Engineering, Indian Institute of Technology Mandi, Kamand 175075, India.
J Phys Condens Matter. 2022 Jun 13;34(32). doi: 10.1088/1361-648X/ac742e.
Both SnS and SnSe have been experimentally and theoretically confirmed as topological crystalline insulators in native rocksalt structure. Here, phononic structure, thermodynamic properties and temperature dependent electron-phonon interaction (EPI) have investigated for both the materials in rocksalt phase. Previously performed theoretical studies have predicted the phase instability of SnS in this crystal structure at ambient condition. But, after a detailed study performing on the phonon calculation of SnS, we have predicted the phase stability of SnS with considering the Sn 4orbitals as valence states incalculation. The importance of long range Coulomb forces along with the themodynamical properties are also described in detailed for both materials. The computed value of Debye temperature (ΘD) for SnS (SnSe) is ∼315.0 K (∼201.7 K). The preliminary evidence of topological phonon is found along-direction, where the linear band touching is observed as compared to type II Weyl phononic material ZnSe (Liu2021B094306). The topological phase transition is seen for these materials due to EPI, where non-linear temperature dependent bandgap is estimated. The predicted value of transition temperature for SnS (SnSe) is found to be ∼700 K, where after this temperature the non-trivial to trivial topological phase is seen. The strength of EPI shows more stronger impact on the electronic structure of SnS than SnSe material. The reason of non-linear behaviour of bandgap with rise in temperature is discussed with the help of temperature dependent linewidths and lineshifts of conduction band and valence band due to EPI. The present study reveals the phase stability of SnS along with the comparative study of thermal effect on EPI of SnS and SnSe. Further, the possibility of temperature induced topological phase transition provides one of important behaviour to apply these two materials for device making application.
SnS和SnSe均已通过实验和理论证实为具有天然岩盐结构的拓扑晶体绝缘体。在此，对岩盐相中的这两种材料的声子结构、热力学性质以及温度依赖的电子-声子相互作用（EPI）进行了研究。先前进行的理论研究预测了SnS在这种晶体结构中在环境条件下的相不稳定性。但是，在对SnS的声子计算进行详细研究之后，我们在计算中将Sn 4轨道视为价态，从而预测了SnS的相稳定性。还详细描述了长程库仑力的重要性以及这两种材料的热力学性质。SnS（SnSe）的德拜温度（ΘD）计算值约为315.0 K（约201.7 K）。在与II型外尔声子材料ZnSe（Liu2021B094306）相比观察到线性能带接触的方向上发现了拓扑声子的初步证据。由于EPI，这些材料出现了拓扑相变，其中估计了非线性温度依赖的带隙。发现SnS（SnSe）的转变温度预测值约为700 K，在此温度之后会出现从非平凡拓扑相到平凡拓扑相的转变。EPI的强度对SnS的电子结构的影响比对SnSe材料的影响更强。借助于由于EPI导致的导带和价带的温度依赖线宽和线移，讨论了带隙随温度升高的非线性行为的原因。本研究揭示了SnS的相稳定性以及对SnS和SnSe的EPI热效应的比较研究。此外，温度诱导拓扑相变的可能性为将这两种材料应用于器件制造提供了一个重要的行为。
