Excitonic Instability in Ta_(2)Pd_(3)Te_(5) Monolayer  

作　　者：Jingyu Yao Haohao Sheng Ruihan Zhang Rongtian Pang Jin-Jian Zhou Quansheng Wu Hongming Weng Xi Dai Zhong Fang Zhijun Wang 

机构地区：[1]Beijing National Laboratory for Condensed Matter Physics,and Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China [2]University of Chinese Academy of Sciences,Beijing 100049,China [3]Centre for Quantum Physics,Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement(MOE),School of Physics,Beijing Institute of Technology,Beijing 100081,China [4]Department of Physics,Hong Kong University of Science and Technology,Hong Kong 999077,China

出　　处：《Chinese Physics Letters》2024年第9期57-62,共6页中国物理快报（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.11974395 and 12188101);the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33000000);the National Key R&D Program of China(Grant Nos.2022YFA1403800 and 2022YFA1403400);the Center for Materials Genome。

摘　　要：By systematic theoretical calculations,we reveal an excitonic insulator(EI)in the Ta_(2)Pd_(3)Te_(5)monolayer.The bulk Ta_(2)Pd_(3)Te_(5)is a van der Waals(vdW)layered compound,whereas the vdW layer can be obtained through exfoliation or molecular-beam epitaxy.First-principles calculations show that the monolayer is a nearly zero-gap semiconductor with the modified Becke–Johnson functional.Due to the same symmetry of the band-edge states,the two-dimensional polarization 2D would be finite as the band gap goes to zero,allowing for an EI state in the compound.Using the first-principles many-body perturbation theory,the GW plus Bethe–Salpeter equation calculation reveals that the exciton binding energy is larger than the single-particle band gap,indicating the excitonic instability.The computed phonon spectrum suggests that the monolayer is dynamically stable without lattice distortion.Our findings suggest that the Ta_(2)Pd_(3)Te_(5) monolayer is an excitonic insulator without structural distortion.

关 键 词：MONOLAYER PRINCIPLES CALCULATIONS 

分 类 号：O469[理学—凝聚态物理]