Coulomb Interaction In Quantum Dot Research Articles

Thermoelectric transport through a finite-U quantum dot side-coupled to Majorana bound state

We study the thermoelectric transport through a single-level quantum dot (QD) coupled to two normal metallic leads and side-coupled to Majorana bound state (MBS). The Coulomb interaction in QD is considered. To investigate only the influence of MBS on thermoelectric transport, we focus on the relatively high temperature region ($T\gg T_K$), where Kondo effect does not appear. The electric and thermal conductance and thermopower as a function of gate voltage (i.e. QD level) are completely different whether the coupling between MBSs is zero or not. When the coupling between MBSs is finite, all thermoelectric characteristics are similar to the transport without MBS. However, for zero MBSs' coupling, the electric and thermal conductance peaks are reduced by 3/4. Especially, in the case of QD without MBS, the sign of thermopower changes three times, however, in the case of QD strongly side-coupled to ideal and isolated MBS, the sign of thermopower changes 9 or 5 times. It can be used for detecting of the signature of MBS. It has actual possibilities when the nanowire is long enough and pure without any defects.

Electronic transport through a Majorana bound state coupled to a T-shaped quantum-dot system with Coulomb interaction

Using the Green’s function technique, we respectively investigate the electron transport properties of two spin components through the system of a T-shaped double quantum dot structure coupled to a Majorana bound state, in which only one quantum dot is connected with two metallic leads. We explore the interplay between the Fano effect and the MBSs for different dot-MBS coupling strength λ, dot-dot coupling strength t, and MBS-MBS coupling strength e M in the noninteracting case. Then the Coulomb interaction and magnetic field effect on the conductance spectra are investigated. Our results indicate that G ↓(ω) is not affected by the Majorana bound states, but a “0.5” conductance signature occurs in the vicinities of Fermi level of G ↑(ω). This robust property persists for a wide range of dot-dot coupling strength and dot-MBS coupling strength, but it can be destroyed by Coulomb interaction in quantum dots. By adjusting the size and direction of magnetic field around the quantum dots, the “0.5” conductance signature damaged by U can be restored. At last, the spin magnetic moments of two dots by applying external magnetic field are also predicted.

A nonlinear Bloch model for Coulomb interaction in quantum dots

In this paper, we first derive a Coulomb Hamiltonian for electron–electron interaction in quantum dots in the Heisenberg picture. Then we use this Hamiltonian to enhance a Bloch model, which happens to be nonlinear in the density matrix. The coupling with Maxwell equations in case of interaction with an electromagnetic field is also considered from the Cauchy problem point of view. The study is completed by numerical results and a discussion about the advisability of neglecting intra-band coherences, as is done in part of the literature.

Control of shell filling with Coulomb interaction in quantum dots side‐coupled to quantum wires

AbstractWe report the control of the orbital occupation by using the intra‐orbital Coulomb interaction in quantum dots Tcoupled to quantum wires. With the change of the confinement potential, intra‐orbital Coulomb interaction exceeds orbital level spacing and influences the orbital occupation. We realize such potential modification by changing either the gate design or the voltages applied to the gates. The rearrangement of the orbital occupation is confirmed from the response of the addition energy spectroscopy to the magnetic field. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Phase breaking of nonequilibrium electrons in a ballistic quantum dot

A study of phase breaking of equilibrium and nonequilibrium electrons in a ballistic quantum dot is presented. Estimates for the phase breaking time are obtained from the magnitude of the weak-localization peak, observed in the conductance on sweeping either magnetic field or dc bias voltage. These investigations reveal that the phase breaking of equilibrium and nonequilibrium electrons exhibits the same functional dependence on energy. In particular, at sufficiently high energies the phase breaking time is found to vary as an inverse square law of energy, consistent with predictions for electron-electron scattering due to Coulomb interaction in quantum dots. At lower energies, however, a saturation in the phase breaking rate is observed, the onset of which is found to be well correlated to the average level spacing of the dot.

Ultrafast energy relaxation in quantum dots.

By use of femtosecond differential absorption spectroscopy the electron-hole pair relaxation times have been determined in CdSe quantum dots with excited state energies larger than the LO-phonon energy. The fast energy relaxation within 500 fs is independent of the relation between level spacing and LO-phonon energy and shows no bottleneck effect. The population dynamics is mainly governed by the hole relaxation process. With increasing intensity, the formation of two-pair states (biexcitons) of various energies dominates the population dynamics due to the strong influence of Coulomb interaction in quantum dots even in the strong confinement. At high pair densities, the created two-pair states mediate a new relaxation path due to their stimulated decay into one photon and one electron-hole pair with lower energy.