  The out-of-equilibrium many-body quantum dynamics of an interacting Bose gas
trapped in a one-dimensional composite double-well potential is studied by
solving the many-body Schr\"odinger equation numerically accurately by
employing the multiconfigurational time-dependent Hartree for bosons (MCTDHB)
method. The composite double-well is formed by merging two deformed harmonic
wells having a hump at their centre. We characterised the dynamics by the time
evolution of survival probability, fragmentation, and many-particle position
and momentum variances. Our study demonstrates the prominent role played by the
higher orbitals in the dynamics and thereby highlighted the necessity of a
many-body technique like MCTDHB which can take into account all the relevant
orbitals for the accurate description of complex many-body dynamics. Further,
we showed that the universality of fragmentation with respect to the number of
particles corresponding to a particular interaction strength is also exhibited
by the higher-order orbitals. Therefore, it is a robust phenomenon not limited
to systems that can be described by two orbitals only.
