Kavli Affiliate: Birgitta Whaley
| First 5 Authors: Cian C. Reeves, Gaurav Harsha, Avijit Shee, Yuanran Zhu, Chao Yang
| Summary:
Theoretical descriptions of non equilibrium dynamics of quantum many-body
systems essentially employ either (i) explicit treatments, relying on
truncation of the expansion of the many-body wave function, (ii) compressed
representations of the many-body wave function, or (iii) evolution of an
effective (downfolded) representation through Green’s functions. In this work,
we select representative cases of each of the methods and address how these
complementary approaches capture the dynamics driven by intense field
perturbations to non equilibrium states. Under strong driving, the systems are
characterized by strong entanglement of the single particle density matrix and
natural populations approaching those of a strongly interacting equilibrium
system. We generate a representative set of results that are numerically exact
and form a basis for critical comparison of the distinct families of methods.
We demonstrate that the compressed formulation based on similarity transformed
Hamiltonians (coupled cluster approach) is practically exact in weak fields
and, hence, weakly or moderately correlated systems. Coupled cluster, however,
struggles for strong driving fields, under which the system exhibits strongly
correlated behavior, as measured by the von Neumann entropy of the single
particle density matrix. The dynamics predicted by Green’s functions in the
(widely popular) GW approximation are less accurate by improve significantly
upon the mean-field results in the strongly driven regime.
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