Trends in the electronic structure of borophene polymorphs

Borophene is a two-dimensional material made out of boron atoms only. It exhibits polymorphism
and different allotropes can be studied in terms of a rigid electronic structure, where only the
occupation of the states change with the respect to the number of electrons available in the system
(self-doping). In this work we selected a set of representative borophene polymorphs (δ3 , δ5 , δ6 , β12
α1 , α′ , α′ -Bilayer) and studied the shared features of their electronic structures and the limitations
of this model. Our work revealed the appearance of defect-like states in some polymorphs when
related to a parent rigid electronic structure, and bonding/antibonding monolayer-like states in
the α′ -Bilayer. Moreover, we show how the buckling of δ6 and α′ can act as a tuning parameter,
enabling semimetallicity, Dirac cones, and nesting of the Fermi surface. In light of their promises
for exotic but also useful behavior, we expect our work to foster the interest in larger and more
complex borophene structures.