Realization of 2D metals at the ångström thickness limit.

Two-dimensional (2D) metals are appealing for many emergent phenomena and have recently attracted research interests. Unlike the widely studied 2D van der Waals (vdW) layered materials, 2D metals are extremely challenging to achieve, because they are thermodynamically unstable. Here we develop a vdW squeezing method to realize diverse 2D metals (including Bi, Ga, In, Sn and Pb) at the ångström thickness limit. The achieved 2D metals are stabilized from a complete encapsulation between two MoS monolayers and present non-bonded interfaces, enabling access to their intrinsic properties. Transport and Raman measurements on monolayer Bi show excellent physical properties, for example, new phonon mode, enhanced electrical conductivity, notable field effect and large nonlinear Hall conductivity. Our work establishes an effective route for implementing 2D metals, alloys and other 2D non-vdW materials, potentially outlining a bright vision for a broad portfolio of emerging quantum, electronic and photonic devices.