6 research outputs found
Time-dependent transport through a T-coupled quantum dot
We are considering the time-dependent transport through a discrete system,
consiting of a quantum dot T-coupled to an infinite tight-binding chain. The
periodic driving that is induced on the coupling between the dot and the chain,
leads to the emergence of a characteristic multiple Fano resonant profile in
the transmission spectrum. We focus on investigating the underlying physical
mechanisms that give rise to the quantum resonances. To this end, we use
Floquet theory for calculating the transmission spectrum and in addition employ
the Geometric Phase Propagator (GPP) approach [Ann. Phys. 375, 351 (2016)] to
calculate the transition amplitudes of the time-resolved virtual processes, in
terms of which we describe the resonant behavior. This two fold approach,
allows us to give a rigorous definition of a quantum resonance in the context
of driven systems and explains the emergence of the characteristic Fano profile
in the transmission spectrum.Comment: 9 pages, 4 figure
Latent symmetry induced degeneracies
Degeneracies in the energy spectra of physical systems are commonly
considered to be either of accidental character or induced by symmetries of the
Hamiltonian. We develop an approach to explain degeneracies by tracing them
back to symmetries of an effective Hamiltonian derived by subsystem
partitioning. We provide an intuitive interpretation of such latent symmetries
by relating them to corresponding local symmetries in the powers of the
underlying Hamiltonian matrix. As an application, we relate the degeneracies
induced by the rotation symmetry of a real Hamiltonian to a non-abelian latent
symmetry group. It is demonstrated that the rotational symmetries can be broken
in a controlled manner while maintaining the underlying more fundamental latent
symmetry. This opens up the perspective of investigating accidental
degeneracies in terms of latent symmetries