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Lifting the Franck-Condon blockade in driven quantum dots Haughian, Patrick ; ; et al in Physical Review. B : Condensed Matter (2016), 94 Electron-vibron coupling in quantum dots can lead to a strong suppression of the average current in the sequential tunneling regime. This effect is known as Franck-Condon blockade and can be traced back ... [more ▼] Electron-vibron coupling in quantum dots can lead to a strong suppression of the average current in the sequential tunneling regime. This effect is known as Franck-Condon blockade and can be traced back to an overlap integral between vibron states with different electron numbers which becomes exponentially small for large electron-vibron coupling strength. Here, we investigate the effect of a time-dependent drive on this phenomenon, in particular the effect of an oscillatory gate voltage acting on the electronic dot level. We employ two different approaches: perturbation theory based on nonequilibrium Keldysh Green's functions and a master equation in Born-Markov approximation. In both cases, we find that the drive can lift the blockade by exciting vibrons. As a consequence, the relative change in average current grows exponentially with the drive strength. [less ▲] Detailed reference viewed: 5 (0 UL)Excitons in boron nitride single layer ; Paleari, Fulvio ; Pereira Coutada Miranda, Henrique et al in Physical Review. B : Condensed Matter (2016), 94(125303), Boron nitride single layer belongs to the family of two-dimensional materials whose optical properties are currently receiving considerable attention. Strong excitonic effects have already been observed ... [more ▼] Boron nitride single layer belongs to the family of two-dimensional materials whose optical properties are currently receiving considerable attention. Strong excitonic effects have already been observed in the bulk and still stronger effects are predicted for single layers. We present here a detailed study of these properties by combining ab initio calculations and a tight-binding Wannier analysis in both real and reciprocal space. Due to the simplicity of the band structure with single valence (π) and conduction (π∗) bands the tight-binding analysis becomes quasiquantitative with only two adjustable parameters and provides tools for a detailed analysis of the exciton properties. Strong deviations from the usual hydrogenic model are evidenced. The ground-state exciton is not a genuine Frenkel exciton, but a very localized tightly bound one. The other ones are similar to those found in transition-metal dichalcogenides and, although more localized, can be described within a Wannier-Mott scheme. [less ▲] Detailed reference viewed: 105 (9 UL)Temperature-dependent excitonic effects in the optical properties of single-layer MoS2 Molina-Sanchez, Alejandro ; ; et al in Physical Review. B : Condensed Matter (2016), 93 The electron-phonon interaction alters substantially the conventional picture of the band structure. It also changes the properties of excitonic states, which are very pronounced in many 2D materials ... [more ▼] The electron-phonon interaction alters substantially the conventional picture of the band structure. It also changes the properties of excitonic states, which are very pronounced in many 2D materials. Using many-body perturbation theory, the authors describe how the inclusion of temperature modifies the electronic bands of single-layer MoS2. Different bands and different regions in the Brillouin zone are affected in different ways by electron-phonon coupling. Using the temperature-broadened bands as input for the Bethe-Salpeter equation, the authors explain why, for the bound A and B excitons, the electron-phonon coupling changes mainly the position, and for the C exciton, only the width is affected by temperature, while the energy is rather constant. [less ▲] Detailed reference viewed: 136 (11 UL)Dipolar spin-misalignment correlations in inhomogeneous magnets: Comparison between neutron scattering and micromagnetic ; ; Michels, Andreas in Physical Review. B : Condensed Matter (2015), 92(1), 014427 In inhomogeneous bulk ferromagnets, the dominating sources of spin disorder are related to spatial variations of (i) the magnitude of the local saturation magnetization and of (ii) the magnitude and/or ... [more ▼] In inhomogeneous bulk ferromagnets, the dominating sources of spin disorder are related to spatial variations of (i) the magnitude of the local saturation magnetization and of (ii) the magnitude and/or direction of the magnetic anisotropy field. For the particular example of a porous ferromagnet, where the magnetization inhomogeneity is at maximum, we demonstrate, by means of experimental neutron scattering data and micromagnetic simulations, the anisotropic character of magnetization fluctuations induced by the dipolar interaction. [less ▲] Detailed reference viewed: 23 (0 UL)Detecting nonlocal Cooper pair entanglement by optical Bell inequality violation ; ; et al in Physical Review. B : Condensed Matter (2015), 91 Based on the Bardeen Cooper Schrieffer (BCS) theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to ... [more ▼] Based on the Bardeen Cooper Schrieffer (BCS) theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the produced photon pairs can be used to violate a Bell inequality, unambiguously demonstrating the entanglement of the split Cooper pairs. [less ▲] Detailed reference viewed: 20 (0 UL)F center in lithium fluoride revisited: Comparison of solid-state physics and quantum-chemistry approaches ; ; et al in Physical Review. B : Condensed Matter (2014), 89 We revisit the theoretical description of the F color center in lithium fluoride employing advanced complementary ab initio techniques.We compare the results from periodic supercell calculations involving ... [more ▼] We revisit the theoretical description of the F color center in lithium fluoride employing advanced complementary ab initio techniques.We compare the results from periodic supercell calculations involving density-functional theory (DFT) and post-DFT techniques with those from the embedded-cluster approach involving quantumchemical many-electron wave-function techniques. These alternative approaches yield results in good agreement with each other and with the experimental data provided that correlation effects are properly taken into account. [less ▲] Detailed reference viewed: 79 (7 UL)Electronic structure of atomically coherent square semiconductor superlattices with dimensionality below two Kalesaki, Efterpi ; ; et al in Physical Review. B : Condensed Matter (2013), 88(11), 9 Detailed reference viewed: 41 (1 UL)Effective fluctuation theorems for electron transport in a double quantum dot coupled to a quantum point contact Bulnes Cuetara, Gregroy ; Esposito, Massimiliano ; et al in Physical Review. B : Condensed Matter (2013), 88(115134), A theoretical study is reported of electron transport at finite temperature in a double quantum dot (DQD) capacitively coupled to a quantum point contact (QPC) for the measurement of the DQD charge state ... [more ▼] A theoretical study is reported of electron transport at finite temperature in a double quantum dot (DQD) capacitively coupled to a quantum point contact (QPC) for the measurement of the DQD charge state. Starting from a Hamiltonian model, a master equation is obtained for the stochastic process taking place in the DQD while the QPC is at or away from equilibrium, allowing us to study the measurement back-action of the QPC onto the DQD. The QPC is treated nonperturbatively in our analysis. Effective fluctuation theorems are established for the full counting statistics of the DQD current under different limiting conditions. These fluctuation theorems hold with respect to an effective affinity characterizing the nonequilibrium environment of the DQD and differing from the applied voltage if the QPC is out of equilibrium. The effective affinity may even change its sign if the Coulomb drag of the QPC reverses the DQD current. The thermodynamic implications of the effective fluctuation theorems are discussed. [less ▲] Detailed reference viewed: 51 (5 UL)Semiempirical pseudopotential approach for nitride-based nanostructures and ab initio based passivation of free surfaces Molina-Sanchez, Alejandro ; ; in Physical Review. B : Condensed Matter (2012), 86 Detailed reference viewed: 25 (2 UL)Fluctuation theorems for capacitively coupled electronic currents Bulnes Cuetara, Gregroy ; Esposito, Massimiliano ; in Physical Review. B : Condensed Matter (2011) The counting statistics of electron transport is studied theoretically in a system with two capacitively coupled parallel transport channels. Each channel is composed of a quantum dot connected by ... [more ▼] The counting statistics of electron transport is studied theoretically in a system with two capacitively coupled parallel transport channels. Each channel is composed of a quantum dot connected by tunneling to two reservoirs. The nonequilibrium steady state of the system is controlled by two affinities or thermodynamic forces, each one determined by the two reservoirs of each channel. The status of a single-current fluctuation theorem is investigated starting from the fundamental two-current fluctuation theorem, which is a consequence of microreversibility. We show that the single-current fluctuation theorem holds in the limit of a large Coulomb repulsion between the two parallel quantum dots, as well as in the limit of a large current ratio between the parallel channels. In this latter limit, the symmetry relation of the single-current fluctuation theorem is satisfied with respect to an effective affinity that is much lower than the affinity determined by the reservoirs. This backaction effect is characterized quantitatively. [less ▲] Detailed reference viewed: 25 (0 UL)Physics of imaging p-n junctions by scanning tunneling microscopy and spectroscopy ; Marso, Michel ; et al in Physical Review. B : Condensed Matter (2003), ((2003)), 165307 Combined voltage-dependent scanning tunneling microscopy ~STM! images with atomic resolution, local scanning tunneling spectroscopy, and simulations of the potential distribution in the interface STM tip ... [more ▼] Combined voltage-dependent scanning tunneling microscopy ~STM! images with atomic resolution, local scanning tunneling spectroscopy, and simulations of the potential distribution in the interface STM tip system are used to extract the physical imaging mechanisms of GaAs p-n interfaces in STM images. It is shown that ~i! the tip-induced changes of the potential near the interface result in the tunneling characteristics of the p-type (n-type! layer being dragged into the interfaces’ depletion region at positive ~negative! sample voltage. ~ii! This leads to a considerable reduction of the apparent width of the image of the depletion zone in STM images. ~iii! At small negative sample voltages, a pronounced depression line appears. The depression is directly correlated with the electronic interface. It arises from the interplay of competing current contributions from the valence and conduction bands. This understanding of the imaging process allows us to develop methods on how to extract accurate physical data about the properties of the electronic interfaces from scanning tunneling microscopy images. [less ▲] Detailed reference viewed: 12 (0 UL)Oscillations in the magnetoconductance autocorrelation function for ballistic microstructures ; Wirtz, Ludger ; et al in Physical Review. B : Condensed Matter (1998), 57(16), 9875-9878 We present a comparison between experiment and theory for the magnetoconductance autocorrelation function C(Delta B) for transport through a stadium-shaped ballistic microstructure. The correlation ... [more ▼] We present a comparison between experiment and theory for the magnetoconductance autocorrelation function C(Delta B) for transport through a stadium-shaped ballistic microstructure. The correlation function displays damped oscillations which can be traced to the quantum interference between bundles of short trajectories. We present two different semiclassical calculations applicable for large and small mode numbers of the quantum wire, respectively. Good agreement is found with experimental data taken at relatively low mode numbers. [S0163-1829(98)03316-5]. [less ▲] Detailed reference viewed: 20 (0 UL) |
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