Carlos A. Parra-Murillo

Two-band Bose-Hubbard model for many-body resonant tunneling in the Wannier-Stark system

We study an experimentally realizable paradigm of complex many-body quantum systems, a two-band Wannier-Stark model, for which diffusion in Hilbert space as well as many-body Landau-Zener processes can be engineered. A cross-over between regular to quantum chaotic spectra is found within the many-body avoided crossings at resonant tunneling conditions. The spectral properties are shown to determine the evolution of states across a cascade of Landau-Zener events. We apply the obtained spectral information to study the non-equilibrium dynamics of our many-body system in different parameter regimes.

Exact numerical methods for a many-body Wannier–Stark system

Abstract We present exact methods for the numerical integration of the Wannier–Stark system in a many-body scenario including two Bloch bands. Our ab initio approaches allow for the treatment of a few-body problem with bosonic statistics and strong interparticle interaction. The numerical implementation is based on the Lanczos algorithm for the diagonalization of large, but sparse symmetric Floquet matrices. We analyze the scheme efficiency in terms of the computational time, which is shown to scale polynomially with the size of the system. The numerically computed eigensystem is applied to the analysis of the Floquet Hamiltonian describing our problem. We show that this allows, for instance, for the efficient detection and characterization of avoided crossings and their statistical analysis. We finally compare the efficiency of our Lanczos diagonalization for computing the temporal evolution of our many-body system with an explicit fourth order Runge–Kutta integration. Both implementations heavily exploit efficient matrix–vector multiplication schemes. Our results should permit an extrapolation of the applicability of exact methods to increasing sizes of generic many-body quantum problems with bosonic statistics.

Non-hermitian approach to decaying ultracold bosonic systems

A paradigm model of modern atom optics is studied, strongly interacting ultracold bosons in an optical lattice. This many-body system can be artificially opened in a controlled manner by modern experimental techniques. We present results based on a non-hermitian effective Hamiltonian whose quantum spectrum is analyzed. The direct access to the spectrum of the metastable many-body system allows us to easily identify relatively stable quantum states, corresponding to previously predicted solitonic many-body structures.

Simultaneous positive and negative photocurrent response in asymmetric quantum dot infrared photodetectors

We study the influence on the photocurrent of the final state in bound-to-quasibound transitions in self-assembled quantum dot infrared photodetectors. We investigate two structures designed to explore different mechanisms of carrier extraction and therefore achieve a better insight on these processes. We observe photocurrent in opposite directions, with positive and negative sign, for different incident frequencies at the same applied external electric field. This phenomenon is attributed to the asymmetry of the potential barriers surrounding the quantum dots.

Generation of robust entangled states in a non-Hermitian periodically driven two-band Bose-Hubbard system

A many-body Wannier-Stark system coupled to an effective reservoir is studied within a non-Hermitian approach in the presence of a periodic driving. We show how the interplay of dissipation and driving dynamically induces a subspace of states which are very robust against dissipation. We numerically probe the structure of these asymptotic states and their robustness to imperfections in the initial-state preparation and to the size of the system. Moreover, the asymptotic states are found to be strongly entangled making them interesting for further applications.

Occupation-Constrained Interband dynamics of a Non-Hermitian Two-Band Bose–Hubbard Hamiltonian

The interband dynamics of a two-band Bose-Hubbard model is studied with strongly correlated bosons forming single-site double occupancies referred to as doublons. Our model for resonant doublon interband coupling exhibits interesting dynamical features such as quantum Zeno effect, the generation of states such as a two-band Bell-like state and an upper-band Mott-like state. The evolution of the asymptotic state is controlled here by the effective opening of one or both of the two bands, which models decay channels.

Off-resonant many-body quantum carpets in strongly tilted optical lattices

An unit filling Bose-Hubbard Hamilonian embedded in strong Stark field is studied in the off-resonant regime inhibiting single and many-particle first order tunneling resonances. We investigate the occurrence of coherent dipole wave-like propagation along of an optical lattice by means of an effective Hamiltonian accounting for second order tunneling processes. It is shown that dipole wavefunction evolution in the short-time limit is ballistic and that finite size effects induce dynamical self-interference patterns known as quantum carperts. We also present the effects of the border right after the first reflection showing that the wavefunction diffuses normally with the variance changing linearly in time. This work extends the rich physical phenomenology of the tilted one dimensional lattice systems in a scenario of many interacting quantum particles, the so-called many-body Wannier-Stark system.

Chaotic level mixing in a two-band Bose-Hubbard model

We present a two-band Bose-Hubbard model which is shown to be minimal in the necessary coupling terms at resonant tunneling conditions. The dynamics of the many-body problem is studied by sweeping the system across an avoided level crossing. The linear sweep generalizes Landau-Zener transitions from single-particle to many-body realizations. The temporal evolution of single- and two-body observables along the sweeps is investigated in order to characterize the non-equilibrium dynamics in our complex quantum system.

Exceptionally Narrow-Band Quantum Dot Infrared Photodetector

InGaAlAs/InGaAs/InGaAlAs/InAs/InP quantum-dot structures have been investigated for the development of infrared photodetectors capable of generating photocurrent peaks exceptionally narrow for sharp wavelength discrimination. Our specially designed structure displays a photocurrent peak at 12

Many-body resonant tunneling in the Wannier-Stark system

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