  Magic-angle twisted bilayer graphene is a tunable material with remarkably
flat energy bands near the Fermi level, leading to fascinating transport
properties and correlated states at low temperatures. However, grown pristine
samples of this material tend to break up into landscapes of twist-angle
domains, strongly influencing the physical properties of each individual
sample. This poses a significant problem to the interpretation and comparison
between measurements obtained from different samples. In this work, we study
numerically the effects of twist-angle disorder on quantum electron transport
in mesoscopic samples of magic-angle twisted bilayer graphene. We find a
significant property of twist-angle disorder that distinguishes it from
onsite-energy disorder: it leads to an asymmetric broadening of the
energy-resolved conductance. The magnitude of the twist-angle variation has a
strong effect on conductance, while the number of twist-angle domains is of
much lesser significance. We further establish a relationship between the
asymmetric broadening and the asymmetric density of states of twisted bilayer
graphene at angles smaller than the first magic angle. Our results show that
the qualitative differences between the types of disorder in the
energy-resolved conductance of twisted bilayer graphene samples can be used to
characterize them at temperatures above the critical temperatures of the
correlated phases, enabling systematic experimental studies of the effects of
the different types of disorders also on the other properties such as the
competition of the different types of correlated states appearing at lower
temperatures.
