[NCTS Physics Research Highlights] Horng-Tay Jeng & Chung-Hou Chung 'Proximity induced charge density wave in a garphene1T-TaS2 heterostructure', Nature Communications 15, 8056 (2024)

• 2024-10-04
• Chen, Jhan Yu 陳詹喻
• Computational quantum materials Strongly correlated condensed matter and cold atom systems Condensed Matter

Proximity induced charge density wave in a garphene1T-TaS2 heterostructure
因鄰近效應於石墨烯與二硫化鉭雙層異質結構中引起之電荷密度波

Nikhil Tilak, Michael Altvater, Sheng-Hsiung Hung, Choong-Jae Won, Guohong Li, Taha Kaleem, Sang-Wook Cheong, Chung-Hou Chung*, Horng-Tay Jeng* & Eva Y. Andrei
Nature Communications 15, 8056 (2024)
DOI: https://doi.org/10.1038/s41467-024-51608-y

The proximity-effect, whereby materials in contact appropriate each other’s electronic-properties, is widely used to induce correlated states, such as superconductivity or magnetism, at heterostructure interfaces. Thus far however, demonstrating the existence of proximity-induced charge-density waves (PI-CDW) proved challenging. This is due to competing effects, such as screening or co-tunneling into the parent material, that obscured its presence. Here we report the observation of a PI-CDW in a graphene layer contacted by a 1T-TaS2 substrate. Using scanning tunneling microscopy (STM) and spectroscopy (STS) together with theoretical-modeling, we show that the coexistence of a CDW with a Mott–gap in 1T-TaS2 coupled with the Dirac-dispersion of electrons in graphene, makes it possible to unambiguously demonstrate the PI-CDW by ruling out alternative interpretations. We further show that the mechanism underlying the PI-CDW is well-described by short-range exchange-interactions that are distinctly different from previously observed proximity effects.

「鄰近效應」，即相互接觸的材料之電性能彼此轉移，已廣泛被應用於誘發強關聯電子之量子態，如：在異質介面處之超導態或磁性量子態。然而，當今要證明因鄰近效應而產生之電荷密度波（PI-CDW）是非常困難的事。這是因為同時有其他與之競爭的效應掩蓋其存在，如：電荷之屏蔽或共同穿隧效應。本研究彙集了在石墨烯與二硫化鉭雙層異質結構中於石墨烯層所觀察到PI-CDW效應之結果。我們結合了掃描穿隧顯微鏡，掃描穿隧光譜儀之實驗技術與理論模型計算，共同證明了相位相反之電荷密度波分別存在於具有莫特能隙之二硫化鉭層及與之電荷轉移偶合並具有狄拉克線性能帶之石墨烯層。此結果首次明確證明PI-CDW效應並排除對此實驗現象其他不同之解釋。我們進一步證明此一PI-CDW之形成機制乃因電子於雙層結構間之短距離電荷轉移交互作用所致，不同於所有先前觀察到之其他鄰近效應之形成機制。