[NCTS Physics Research Highlights] Yang-hao Chan 'Observation of possible excitonic charge density waves and metal-insulator transitions in atomically thin semimetals', Nat. Phys. 20, 597-602 (2024)

• 2024-05-22
• Chen, Jhan Yu 陳詹喻
• Computational quantum materials Condensed Matter

Observation of possible excitonic charge density waves and metal-insulator transitions in atomically thin semimetals
在原子尺度薄層半金屬中發現可能的激子電荷密度波和金屬-絕緣體相變

Qiang Gao, Yang-hao Chan*, Pengfei Jiao, Haiyang Chen, Shuaishuai Yin, Kanjanaporn Tangprapha, Yichen Yang, Xiaolong Li, Zhengtai Liu, Dawei Shen, Shengwei Jiang & Peng Chen
Nature Physics 20, 597-602 (2024)
DOI: https://doi.org/10.1038/s41567-023-02349-0

In solids, the condensation of electron and hole pairs with finite momentum leads to an ordered state known as a charge density wave. The origin of the transition has been debated as lattice symmetry breaking and the accompanying relocation of the ions can also leads to  changes the charge distribution. Here we demonstrate a condensed phase in low-dimensional HfTe2. Angle-resolved photoemission spectroscopy measurements reveal a metal–insulator transition and the emergence of replica bands at low temperature which are consistent with a charge density wave ground state. Raman spectroscopy shows no sign of lattice distortion within the detection limit. Our results indicate a possible excitonic insulator phase in low-dimensional HfTe2 without any structural modification.

在固體中，具有有限動量的電子和電洞對的凝聚會產生稱為電荷密度波的有序狀態。此有序態的起源也可能為晶格對稱性破缺，及伴隨的離子的重新定位導致的電荷分佈的變化。在這工作中，我們展示了低維 HfTe2的凝聚相。角分辨光電子能譜測量在低溫下揭示了電荷密度波的金屬-絕緣體轉變以及複製能帶的出現。拉曼光譜在檢測極限內沒有顯示出晶格畸變的跡象。我們的結果表明，低維 HfTe2中可能存在不具結構轉變得激子絕緣體相。