Search results for "Schroedinger equation"

A non-relativistic model for the $[cc][\bar{c}\bar{c}]$ tetraquark

2017

We use a non-relativistic model to study the spectroscopy of a tetraquark composed of $[cc][\bar{c}\bar{c}]$ in a diquark-antidiquark configuration. By numerically solving the Schr\"{o}dinger equation with a Cornell-inspired potential, we separate the four-body problem into three two-body problems. Spin-dependent terms (spin-spin, spin-orbit and tensor) are used to describe the splitting structure of the $c\bar{c}$ spectrum and are also extended to the interaction between diquarks. Recent experimental data on charmonium states are used to fix the parameters of the model and a satisfactory description of the spectrum is obtained. We find that the spin-dependent interaction is sizable in the …

The table top high frequency lasing device

2015

Atomic and molecular systems, subjected to intense laser pulse, emit typical High-Order Armonic Generation (HHG) spectra. This work aims to investigate the possibility to obtain a laser device by HHG. At this end, we analyzed the emission spectra by a molecular ion driven by a linearly polarized laser field. The temporal behaviour is obtained using the Morlet wavelets transform of emission. The results show that, after filtration of the electromagnetic radiation emitted, it is possible to select a frequency which seems to have almost constant intensity and phase. This characteristic makes possible that HHG from a molecule can be used as high frequency laser fields.

Chaos and nonlinearities in high harmonic generation

2016

Linearity is a fundamental postulate of quantum mechanics which is occasionally the subject of debate. This paper investigates the possibility of checking this assumption by using a laser field. We study the corrections caused by the presence of a small nonlinearity in the Hamiltonian of a quantum system. As a model we use a simplified two-level quantum system whose states are coupled by a small off-diagonal term proportional to the population of the upper level. The nonlinearity causes spontaneous decay of the upper level, shift and broadening of the line and the sensitive dependence of the final state on the initial condition. The presence of a strong laser field, resonant with the atomic…

High-order-harmonic generation in dimensionally reduced systems

2013

The time-dependent wave function of a nanoring driven by a laser field is obtained by exploiting the symmetries inherent to the system and used for studying the properties of the electromagnetic radiation emitted by the nanoring as a function of the polarization state of the laser. The diffused radiation has the characteristics of high-order-harmonic generation. For a noncircularly polarized laser field an extension of the expected cutoff position is evident, indicating that nanorings are efficient sources of radiation. The polarization state of the emitted harmonics can be opportunely controlled by varying the parameters of the pump field. The profile of the absorbed angular moment shows t…

Thermal solitons in nanotubes

2022

Starting from a recent proposal of a nonlinear Maxwell-Cattaneo equation for the heat transport with relaxational effects at nanoscale, in a special case of thermal-wave propagation we derive a nonlinear Schrodinger equation for the amplitudes of the heatflux perturbation. The complete integrability of the obtained equation is investigated in order to prove the existence of infinite conservation laws, as well as the existence of infinite exact solutions. In this regards, we have considered the simplest nontrivial solutions, namely, the bright and dark (thermal) solitons, which may be interesting for energy transport and for information transmission in phononic circuits. (c) 2022 Elsevier B.…

A 1D coupled Schrödinger drift-diffusion model including collisions

2005

We consider a one-dimensional coupled stationary Schroedinger drift-diffusion model for quantum semiconductor device simulations. The device domain is decomposed into a part with large quantum effects (quantum zone) and a part where quantum effects are negligible (classical zone). We give boundary conditions at the classic-quantum interface which are current preserving. Collisions within the quantum zone are introduced via a Pauli master equation. To illustrate the validity we apply the model to three resonant tunneling diodes.

Modulational instability and generation of self-induced transparency solitons in resonant optical fibers

2009

International audience; We consider continuous-wave propagation through a fiber doped with two-level resonant atoms, which is described by a system of nonlinear Schrodinger-Maxwell-Bloch (NLS-MB) equations. We identify the modulational instability (MI) conditions required for the generation of ultrashort pulses, in cases of both anomalous and normal GVD (group-velocity dispersion). It is shown that the self-induced transparency (SIT) induces non-conventional MI sidebands. The main result is a prediction of the existence of both bright and dark SIT solitons in the anomalous and normal GVD regimes.

Exact quantum dynamics of interacting spin systems subjected to controllable time dependent magnetic fields

2020

Soliton solutions for an higher order nonlinear Schroedinger equation in optical fiber

2008

The new improvements to increase the bit rate in optical fiber require the propagation of pulse whose temporal width is always lesser. This causes the presence of further terms, linear and nonlinear, in the evolution equation of the pulse. The analysis on the complete integrability of the evolution equation, in a fiber optics with local properties and achieved in a previous paper, is improved dealing with the normal dispersion case, which allows the dark soliton propagation. In the last section special efforts are made to propose some interesting soliton solutions both bright and dark.

Properties of the radiation Emitted by a Laser driven quantum Ring

2015

We present the electromagnetic emission from one electron confined in a quantum ring driven by an intense laser field. We consider both a plain ring and one structured by six potential wells that produce a static tangential force. Through a suitable one-dimensional model we numerically solve the associated Schroedinger equation obtaining the correspondent time evolution of the wave-function. We show that the emission is formed by a wide plateau that can be both quasi-continuum or resolved in discrete lines. We study the dependence of the emitted spectra from the polarization status of the external laser field and in particular we concentrate on the intensity of the emitted lines and of thei…