Cove-type edged graphene nanoribbons (CGNRs), constructed by removing several consecutive carbon atoms at both edges of each supercell in zigzag graphene nanoribbons, have attracted considerable interest due to recent advances in bottom-up synthesis and their intriguing quantum phenomena. However, their electronic transport properties remain poorly understood. Here, we perform a comprehensive theoretical study of CGNRs characterized by four structural parameters of nanoribbon width $N$, cove length $l_{\mathrm{c}}$, outermost zigzag-segment length $l_{\mathrm{z}}$, and cove offset $d$ between opposite edges. Our results reveal that nearly all CGNRs exhibit semiconducting behavior, except for metallic configurations with even $N$ and $l_{\mathrm{c}}+l_{\mathrm{z}}=2d$. The bandgap is continuously tunable over a wide range and presents a nonmonotonic dependence on the parameters of $l_{\mathrm{c}}, l_{\mathrm{z}}$, and $d$. In particular, the normalized bandgap can be described by a single parameter of the ratio $d/(l_{\mathrm{c}}+l_{\mathrm{z}})$, which is well fitted by a cosine function. In the presence of edge defects, a transmission gap opens in metallic CGNRs, while robust, quantized conductance peaks persist in the transmission spectra despite an overall reduction in transmission. These results provide general insights into the structure-property relationships of CGNRs and may facilitate engineering graphene-based electronic devices.

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• Transport phenomena
• Graphene
• Nanoribbon
• Green's function methods
• Tight-binding model