1,720,985 research outputs found
Pairing of a few Fermi atoms in one dimension
No full textWe study a few Fermi atoms interacting through attractive contact forces in a one-dimensional trap by means of numerical exact diagonalization. From the combined analysis of energies and wave functions of correlated ground and excited states we find evidence of BCS-like pairing even for very few atoms. For moderate interaction strength, we reproduce the even-odd oscillation of the separation energy observed in [G. Zu ̈rn, A. N. Wenz, S. Murmann, A. Bergschneider, T. Lompe, and S. Jochim, Phys. Rev. Lett. 111, 175302 (2013)]. For strong interatomic attraction the arrangement of dimers in the trap differs from the homogeneous case as a consequence of Pauli blockade in real space
Three interacting atoms in a one-dimensional trap: A benchmark system for computational approaches
No full textWe provide an accurate calculation of the energy spectrum of
three atoms interacting through a contact force in a one-dimensional harmonic
trap, considering both spinful fermions and spinless bosons. We use fermionic
energies as a benchmark for exact-diagonalization technique (also known as full
configuration interaction), which is found to slowly converge in the case of strong
interatomic attraction
Proposed Alteration of Images of Molecular Orbitals Obtained Using a Scanning Tunneling Microscope as a Probe of Electron Correlation
No full textImaging quasi-particle wavefunctions in quantum dots in via tunneling spectroscopy
No full textWe show that in quantum dots the physical quantities probed by local tunneling spectroscopies-namely, the quasiparticle wave functions of interacting electrons-can considerably deviate from their single-particle counterparts as an effect of Coulomb correlation. From the exact solution of the few-particle Hamiltonian for prototype dots, we find that such deviations are crucial to predict wave function images at low electron densities or high magnetic fields
Correlation effects in quantum dot wave function imaging
No full textWe demonstrate that in semiconductor quantum dots wave functions, its imaged by local tunneling spectroscopies like STM, show characteristic signatures of electron-electron Coulomb correlation. We predict that such images correspond to quasi-particle wave functions which cannot be computed by standard mean-field techniques in the strongly correlated regime. From the configuration-interaction solution of the few-particle problem for prototype dots, we find that quasi-particle wave function images may display signatures of Wigner crystallization
Quantum phases of correlated electrons in artificial molecules under magnetic fields
Full text linkWe investigate the stability of few-electron quantum phases in vertically coupled quantum dots under a magnetic field of arbitrary strength and direction. The orbital and spin stability diagrams of realistic devices containing up to five electrons, from strong to weak interdot coupling, is determined. Correlation effects and realistic sample geometries are fully taken into account within the full configuration interaction method. In general, the magnetic field drives the system into a strongly correlated regime by modulating the single-particle gaps. In coupled quantum dots different components of the field, either parallel or perpendicular to the tunneling direction, affect single-dot orbitals and tunneling energy, respectively. Therefore the stability of the quantum phases is related to different correlation mechanisms, depending on the field direction. Comparison of exact diagonalization results with simple models allows one to identify the specific role of correlations
Visualizing electron correlation by means of ab initio scanning tunneling spectroscopy images of single molecules
No full textCompeting mechanisms for singlet-triplet transition in artificial molecules
Full text linkWe study the magnetic field induced singlet/triplet transition for two electrons in vertically-coupled quantum dots by exact diagonalization of the Coulomb interaction. We identify the different mechanisms occurring in the transition, involving either in-plane correlations or localization in opposite dots, depending on the field direction. Therefore, both spin and orbital degrees of freedom can be manipulated by field strength and direction. The phase diagram of realistic devices is determined
Angle-resolved photoemission spectroscopy from first-principles quantum Monte Carlo
Full text linkAngle-resolved photoemission spectroscopy allows one to visualize in momentum space the probability weight maps of electrons subtracted from molecules deposited on a substrate. The interpretation of these maps usually relies on the plane wave approximation through the Fourier transform of single particle orbitals obtained from density functional theory. Here we propose a first-principle many-body approach based on quantum Monte Carlo (QMC) to directly calculate the quasi-particle wave functions (also known as Dyson orbitals) of molecules in momentum space. The comparison between these correlated QMC images and their single particle counterpart highlights features that arise from many-body effects. We test the QMC approach on the linear C2H2, CO2, and N2 molecules, for which only small amplitude remodulations are visible. Then, we consider the case of the pentacene molecule, focusing on the relationship between the momentum space features and the real space quasi-particle orbital. Eventually, we verify the correlation effects present in the metal CuCl42- planar complex
Quantum phases in artificial molecules
No full textThe few-particle state of carriers confined in a quantum dot is controlled by the balance between their kinetic energy and their Coulomb correlation. In coupled quantum dots, both can be tuned by varying the inter-dot tunneling and interactions. Using a theoretical approach based on the diagonalization of the exact Hamiltonian, we show that the transitions between different quantum phases can be induced through the inter-dot coupling both for a system of few electrons (or holes) and for aggregates of electrons and holes. We discuss their manifestations, in addition energy spectra (accessible through capacitance or transport experiments) and optical spectra. (C) 2001 Elsevier Science Ltd. All rights reserved
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