Louis Felix Feiner

Single-electron tunneling in InP nanowires

We report on the fabrication and electrical characterization of field-effect devices based on wire-shaped InP crystals grown from Au catalyst particles by a vapor–liquid–solid process. Our InP wires are n-type doped with diameters in the 40–55-nm range and lengths of several micrometers. After being deposited on an oxidized Si substrate, wires are contacted individually via e-beam fabricated Ti/Al electrodes. We obtain contact resistances as low as ? 10?k?, with minor temperature dependence. The distance between the electrodes varies between 0.2 and 2 ?m. The electron density in the wires is changed with a back gate. Low-temperature transport measurements show Coulomb-blockade behavior with single-electron charging energies of ? 1?meV. We also demonstrate energy quantization resulting from the confinement in the wire.

Quantum melting of magnetic order due to orbital fluctuations

We have studied the phase diagram and excitations of the spin-orbital model derived for a three dimensional perovskite lattice, as in KCuF_3. The results demonstrate that the orbital degeneracy drastically increases quantum fluctuations and suppresses the classical long-range order near the multicritical point in the mean-field phase diagram. This generates a qualitatively new spin liquid, providing the first example of a valence bond ground state in three dimensions.

The effect of temperature and dot size on the spectral properties of colloidal InP/ZnS core-shell quantum dots.

Visual color changes between 300 and 510 K were observed in the photoluminescence (PL) of colloidal InP/ZnS core-shell nanocrystals. A subsequent study of PL spectra in the range 2-510 K and fitting the temperature dependent line shift and line width to theoretical models show that the dominant (dephasing) interaction is due to scattering by acoustic phonons of about 23 meV. Low temperature photoluminescence excitation measurements show that the excitonic band gap depends approximately inversely linearly on the quantum dot size d, which is distinctly weaker than the dependence predicted by current theories.

Electronic origin of magnetic and orbital ordering in in sulating LaMnO3

We derive a spin-orbital model for insulating

Orbital and spin physics in LiNiO2 and NaNiO2

{\mathrm{LaMnO}}_{3}

Exploring Crystal Phase Switching in GaP Nanowires.

which fulfills the SU(2) symmetry of

Quantum melting of magnetic long-range order near orbital degeneracy : Classical phases and Gaussian fluctuations

S=2

The blocking and Néel temperature in exchange-biased Fe3O4/CoO multilayers

spins at

MAGNETIC AND ORBITAL ORDERING IN THE MANGANITES

{\mathrm{Mn}}^{3+}

Orbital Order Versus Orbital Liquid in Doped Manganites

ions. It includes the complete