  This letter presents a measurement of the nuclear modification factor of
large-radius jets in $\sqrt{s_\mathrm{NN}} = 5.02$ TeV Pb+Pb collisions by the
ATLAS experiment. The measurement is performed using 1.72 nb$^{-1}$ and 257
pb$^{-1}$ of Pb+Pb and $pp$ data, respectively. The large-radius jets are
reconstructed with the anti-$k_{t}$ algorithm using a radius parameter of $R =
1.0$, by re-clustering anti-$k_{t}$ $R = 0.2$ jets, and are measured over the
transverse momentum ($p_{\mathrm{T}}$) kinematic range of $158 < p_{\mathrm{T}}
< 1000$ GeV and absolute pseudorapidity $|y|<2.0$. The large-radius jet
constituents are further re-clustered using the $k_{t}$ algorithm in order to
obtain the splitting parameters, $\sqrt{d_{12}}$ and $\Delta R_{12}$, which
characterize the transverse momentum scale and angular separation for the
hardest splitting in the jet, respectively. The nuclear modification factor,
$R_{\mathrm{AA}}$, obtained by comparing the Pb+Pb jet yields to those in $pp$
collisions, is measured as a function of jet transverse momentum
($p_{\mathrm{T}}$) and $\sqrt{d_{12}}$ or $\Delta R_{12}$. A significant
difference in the quenching of large-radius jets having single sub-jet and
those with more complex substructure is observed. Systematic comparison of jet
suppression in terms of $R_{\mathrm{AA}}$ for different jet definitions is also
provided. Presented results support the hypothesis that jets with hard internal
splittings lose more energy through quenching and provide a new perspective for
understanding the role of jet structure in jet suppression.
