▎ 摘　　要

Hyperbolic metamaterials involving artificially crafted subwavelength structures uniquely interact with light to give extraordinary properties not found in nature. However, both predicting metamaterial candidates and real-izing them are extremely challenging. Preparation processes typically require cutting-edge nanofabrication techniques and are frequently technically or intrinsically impossible. The reported hyperbolic metamaterial systems are merely two-dimensional or assembly of nanostructures. Herein, we report a facile design principle and exemplary fabrication for bulk metamaterials exhibiting tunable hyperbolic dispersions. They are uniquely formed by spontaneous self-assembly reaction between two surface-modified building blocks of few-layer-graphene (FLG) and exfoliated hexagonal boron nitride (h-BN) lamellae. Their mixing ratio, namely, the chem-ical composition of the bulk materials, is a delicate means of controlling hyperbolic responses. Remarkably, a small amount of rhombohedral BN (r-BN) further finely modulates both type-I and type-II hyperbolic dispersions both along in-plane and out-of-plane directions of the bulk materials. The permittivity of our bulk materials obtained by Kramer-Kronig relation exhibits their capability in negative refraction of incident light, and is deli-cately altered by the introduction of r-BN and the change in the composition of the FLG and h-BN building blocks both along in-plane and out-of-plane directions of the bulk materials. In other words, r-BN serves a role as a "dopant" in our h-BN/FLG metamaterials, significantly changing properties of bulk systems. Our achievement can be a new platform to readily design and synthesize bulk metamaterials without complicated preparation methods. It also presents that chemical compositions in our bulk metamaterial system are a facile and predictable means of controlling their properties, striking contrast to conventional metamaterials.