Band Structure Engineering of MXenes for Low‐Loss Visible Epsilon‐Near‐Zero Properties by First‐Principles Calculation

Epsilon‐near‐zero (ENZ) photonics, which exhibit extraordinary capabilities in terms of controlling light–matter interactions, have been attracting increased interest in recent years. However, several challenges still lie ahead, such as large optical loss and the rarity of ENZ candidates, especially in the visible range. Here, by first‐principles calculations, this work proposes dozens of MXenes with promising plasmonic properties that could be potential ENZ candidates with very low loss in the visible range by band structure engineering. Because of the special electronic structures of these MXenes, they all possess quite large screened plasmonic frequencies: ωp/ε∞\[{{\bm{\omega }}_{\bf p}}{\rm{/}}\sqrt {{{\bm{\varepsilon }}_{\bm{\infty }}}} \] , but less than the interband transition onsets, which cause the ENZ properties in these MXenes to appear in the visible range with very low loss (ε2 less than 0.2) by eliminating the interband transition loss at the ENZ frequencies. Furthermore, it is also demonstrated that the ENZ properties in MXenes, including the ENZ frequency and loss, can be effectively tuned upon surface modifications, such as −Cl and −OH. These outstanding ENZ properties, including tunablity and low‐loss, make these MXenes great for potential applications in ENZ photonics, especially in the visible‐light range.