I have been looking into how to maximize the thermoelectric performance of phosphorene through nanostructuring. The mean free path of charge carriers (both e- and h+) is >10nm whereas phonons are around 80 nm. So a nanoribbon of phosphorene of a width 10-80 nm would be ideal.

However, in the attached publication they report the highest ever predicted ZT value of 6.4 comes from a nanoribbon 26 angstroms wide. I feel like I am missing a key detail about why this would be the case. Wouldn't a nanoribbon this narrow reduce electrical conductivity to nearly nothing?