Ultrathin boron nanoribbons: stability, conductivity, and edge magnetism.

We report a systematic density functional theory study of ultrathin boron nanoribbons (BNRs), revealing a rich interplay between structural stability, electronic transport, and magnetism. Two distinct families are considered: compacts-type ribbons built from triangular and square motifs, andsh-type ribbons containing larger polygonal voids. Thes-type members exhibit the highest binding energies and electrical conductivities, while selectedsh-type structures display distinctive electronic features, including a Dirac-like band crossing. Most BNRs are metallic, buts4develops a gap due to quantum confinement ands8becomes semiconducting only in its antiferromagnetic (AFM) ground state. The calculations further identify AFM ordering ins8as robust andsh3as weaker, both arising from edgepstates in analogy to zigzag graphene nanoribbons. Together, these results demonstrate that nanoscale geometry and edge topology decisively tune the properties of BNRs, establishing them as a versatile platform for next-generation nanoelectronic and spintronic devices.