Magnetic-field-induced nonthermal occupation of higher subbands in a three-barrier tunneling structure

When injected electrons in a quantum well first experience an intersubband relaxation process before their escaping by tunneling through a double-barrier structure behind, the magnetic suppression of intersubband LO or LA phonon scattering can give rise to a noticeable nonthermal occupation in higher-lying subbands. That is clearly verified by the relative intensity ratio of the interband photoluminescence spectra for E-2-HH1 and E-1-HH1 transitions. The observed phenomenon may provide an effective method for controlling intersubband scattering rate, a central issue in so-called quantum cascade lasers, and facilitating the population inversion between subbands in quantum wells.

Influence of transverse interdot coupling on transport properties of an Aharonov-Bohm structure composed by two dots and two reservoirs

We derive the modified rate equations for an Aharonov-Bohm (AB) ring with two transversely coupled quantum dots (QD's) embedded in two arms in the presence of a magnetic field. We find that the interdot coupling between the two QD's can cause a temporal oscillation in electron occupation at the initial stage of the quantum dynamics, while the source-drain current decays monotonically to a stationary value. On the other hand, the interdot coupling equivalently divides the AB ring into two coupled subrings. That also destroys the normal AB oscillations with a period of 2pi, and generates new and complex periodic oscillations with their periods varying in a linear manner as the ratio between two magnetic fluxes (each penetrates one AB subring) increases. Furthermore, the interference between two subrings is also evident from the observation of the perturbed fundamental AB oscillation.

Occupation modulation of higher subbands in a three-barrier tunnelling structure with a magnetic field

We verify that the magnetic suppression of intersubband LO or LA phonon scattering can give rise to a noticeable nonthermal occupation in higher-lying subbands. This is clearly determined by the relative intensity ratio of the interband photoluminescence spectra for the E-2 - HH1 and E-1 - HH1 transitions. The observed phenomenon may provide an effective method to control the intersubband scattering rate, which is a key factor of the so-called quantum cascade lasers. This is helpful for the population inversion between both the subbands in quantum wells.

Ground-state properties of an artificial molecule: a simple model calculation for the double quantum dot

The ground state of a double quantum-dot structure is studied by a simplified Anderson-type model. Numerical calculations reveal that the ground-state level of this artificial molecule increases with the increasing single particle level of the dot, and also increases with the decreasing transfer integrals. We show the staircase feature of the electron occupation and the properties of the ground-state eigenvector by varying the;single particle level of the dot.