Tilak Nikhil, Altvater Michael, Hung Sheng-Hsiung, Won Choong-Jae, Li Guohong, Kaleem Taha, Cheong Sang-Wook, Chung Chung-Hou, Jeng Horng-Tay, Andrei Eva Y
Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, New Jersey, USA.
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
Nat Commun. 2024 Sep 14;15(1):8056. doi: 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-TaS 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-TaS coupled with the Dirac-dispersion of electrons in graphene, makes it possible to unambiguously demonstrate the PI-CDW by ruling out alternative interpretations. Furthermore, we find that the PI-CDW is accompanied by a reduction of the Mott gap in 1T-TaS and 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.
近邻效应是指相互接触的材料会相互适配对方的电子特性，该效应被广泛用于在异质结构界面诱导出诸如超导或磁性等关联态。然而到目前为止，证明近邻诱导电荷密度波（PI-CDW）的存在颇具挑战。这是由于诸如屏蔽或共隧穿进入母体材料等竞争效应掩盖了它的存在。在此，我们报告在与1T-TaS衬底接触的石墨烯层中观察到PI-CDW。通过结合扫描隧道显微镜（STM）和光谱学（STS）以及理论建模，我们表明1T-TaS中电荷密度波与莫特能隙的共存，再加上石墨烯中电子的狄拉克色散，使得通过排除其他解释来明确证明PI-CDW成为可能。此外，我们发现PI-CDW伴随着1T-TaS中莫特能隙的减小，并表明PI-CDW背后的机制可以通过与先前观察到的近邻效应明显不同的短程交换相互作用得到很好的描述。
