Three-dimensional Fermi surface of 2H-NbSe_2 - Implications for the mechanism of charge density waves

We investigate the three-dimensional electronic structure of the seminal charge-density-wave (CDW) material 2H-NbSe_2 by soft x-ray angle-resolved photoelectron spectroscopy and density-functional theory. Our results reveal the pronounced 3D character of the electronic structure formed in the quasi-two-dimensional layered crystal structure. In particular, we find a strong dispersion along k_z excluding a nesting-driven CDW formation based on experimental data. The 3D-like band structure of 2H-NbSe_2 has strong implications for the intriguing phase competition of CDW order with superconductivity.