Superconductivity in a Bulk Moire Superlattice Material
Moire materials provide a versatile platform realizing emergent electronic states arising from enhanced correlation due to flat bands. A variety of phenomena including superconductivity, low dimensional ferromagnetism, Mott insulating phase, and topological phenomena have been reported in such systems. To date, moire phenomena have been predominantly explored in artificially assembled low dimensional van der Waals structures, where relative twist and lattice alignment are controlled during device fabrication. Recently, intrinsically grown bulk moire crystals have emerged as a complementary materials platform, in which lattice mismatch between constituent layers generates a coherent moire superlattice throughout the bulk crystal. Here, we report the evidence of bulk superconductivity in single crystals of a recently reported bulk Moire material [Sr6TaS8]1+x[TaS2]8 at ambient pressure. The material exhibits a bulk superconducting transition at Tc = 2.5 K, evidenced consistently by electrical transport, magnetic susceptibility, and heat capacity measurements on single crystals. Structural characterization by X-ray diffraction and atomic resolution electron microscopy establishes the composite, incommensurate crystal structure and scanning tunnelling microscopy reveals a long-wavelength surface modulation due to the incommensurate structure. The observation of bulk superconductivity establishes superconductivity as an emergent phase in this intrinsically synthesized moire material and highlights bulk moire crystals as a promising platform for investigating correlated quantum phenomena beyond artificially assembled two-dimensional structures.