The bias voltage applied to a weakly coupled n-doped GaAs/AlAs superlattice increases the amplitude of the coherent hypersound oscillations generated by a femtosecond optical pulse. This bias-induced amplitude increase and experimentally observed spectral narrowing of the superlattice phonon mode with a frequency 441 GHz provides the evidence for hypersound amplification by stimulated emission ...

The electrical resistivity of Co/Ni and Cu/Ni superlattices exhibit resistivity oscillations as a function of superlattice period L, while Ag/Pd does not. Moreover, the resistivity of Co/Ni superlattices shows quantum size effects and a resistivity enhancement with L, as a function of total film thickness d . These results are consistent with a model which assumes d-electron localization in the...

The effect of the bulk Longitudinal-Optical (LO) phonon on the binding energy is investigated for a shallow donor impurity in a superlattice in the effective mass approximation by using the variational approach. The results are obtained as a function of parameters which characterize the superlattice and the position of the impurity center. The results show that the bulk Longitudinal-Optical (LO...

In this paper, we discuss optical emission, energy transfer and electroluminescence from a superlattice structure containing small ( 2nm diameter) amorphous silicon (Si) clusters coupled to erbium (Er) ions. The superlattice structure is fabricated by direct co-sputtering of thin ( 3–5nm) Er-doped siliconrich nitride/Si (Er:SRN/Si) layers subsequently annealed at different temperatures in order...

Reduction and oxidation in transition-metal oxides are keys to develop technologies related to energy and the environment. Here we report the selective topochemical reduction observed when artificial superlattices with transition-metal oxides are treated at a temperature below 300 °C with CaH(2). [CaFeO(2)](m)/[SrTiO(3)](n) infinite-layer/perovskite artificial superlattice thin films were obtai...

The observation of the quantum Hall effect in an electronic system does not depend on the strict two-dimensionality of the system, but rather that the conductivity in the direction of the magnetic field (ozz) vanishes. This condition can be acheived in a superlattice when the Landau level spacing exceeds the zero-field miniband width of the superlattice. It is now possible to test this criterio...

We develop a theory of interaction effects in graphene superlattices, where tunable superlattice periodicity can be used as a knob to control the gap at the Dirac point. Applied to graphene on hexa-boron-nitride (G/h-BN), our theory predicts substantial many-body enhancement of this gap. Tunable by the moiré superlattice periodicity, a few orders of magnitude enhancement is reachable under opti...

Given the paucity of single phase multiferroic materials (with large ferromagnetic moment), composite systems seem an attractive solution to realize magnetoelectric coupling between ferromagnetic and ferroelectric order parameters. Despite having antiferromagnetic order, BiFeO3 (BFO) has nevertheless been a key material due to excellent ferroelectric properties at room temperature. We studied a...

We discuss a magneto transport and magneto-optical investigation of [211 ]-oriented HgTe-CdTe superlattices. Measurements were performed on seven n-type samples with well widths in the range 41-125 A and energy gaps between 0 and 128 meV. Both magnetotransport and magneto-optical results give evidence for an additional electron species besides the superlattice electrons and holes usually observ...