High-Temperature Excitonic Bose–Einstein Condensate in Centrosymmetric Two-Dimensional Semiconductors,The Journal of Physical Chemistry Letters

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High-Temperature Excitonic Bose–Einstein Condensate in Centrosymmetric Two-Dimensional Semiconductors
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2021-06-04 , DOI: 10.1021/acs.jpclett.1c01370
Dan Wang ₁ , Nannan Luo _{1,

2} , Wenhui Duan ₃ , Xiaolong Zou ₁

Affiliation

The realization of high-temperature excitonic Bose–Einstein condensation (BEC) in practical materials poses great challenges, because of strict constraints in symmetry, exciton binding, lifetime, and interaction. Here, using first-principles methods and symmetry analysis, we propose a new route to realize high-temperature excitonic BEC in centrosymmetric 2D materials, exploiting the parity symmetry of band edges and reduced Coulomb screening. We demonstrate it by taking monolayer TiS₃ as an example, whose lowest-energy exciton shows small exciton mass, small Bohr radius, large binding, and long lifetime simultaneously. The phase diagram of electron–hole systems is further constructed, showing that both BEC and superfluidity can be realized at high temperature and in a broad range of exciton density. Importantly, we reveal that the high-temperature character of excitonic BEC is robust against thickness, beneficial for its experimental observation. By application of this general strategy to 2D materials in the database, monolayer AuBr and BiS₂ are identified as promising candidates for high-temperature excitonic BEC.

中文翻译：

中心对称二维半导体中的高温激子玻色-爱因斯坦凝聚

由于对称性、激子结合、寿命和相互作用的严格限制，在实际材料中实现高温激子玻色-爱因斯坦凝聚 (BEC) 带来了巨大的挑战。在这里，我们使用第一性原理方法和对称性分析，提出了一种在中心对称二维材料中实现高温激子 BEC 的新途径，利用带边缘的奇偶对称性和减少库仑筛选。我们通过采用单层 TiS _{3 来}证明它例如，其最低能量激子同时表现出激子质量小、玻尔半径小、结合大和寿命长。进一步构建了电子-空穴系统的相图，表明 BEC 和超流体都可以在高温和宽激子密度范围内实现。重要的是，我们揭示了激子 BEC 的高温特性对厚度具有鲁棒性，有利于其实验观察。通过将这种通用策略应用于数据库中的二维材料，单层 AuBr 和 BiS ₂被确定为高温激子 BEC 的有希望的候选者。

更新日期：2021-06-17

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