arXiv subjects

H. Z. Song

Publications and source records attributed to H. Z. Song.

5 recordsLinked to original sources

arXiv2006

Time domain optical manipulation of exciton and nuclear spin in a single self-assembled quantum dot

We have demonstrated experimentally the manipulation of exciton and nuclear spins in a single self-assembled In$_{0.75}$Al$_{0.25}$As/Al$_{0.3}$Ga$_{0.7}$As quantum dot. The oscillation of exciton and nuclear spin polarizations were clearly observed. The switching of the emissions in Zeeman split pair indicates that the exciton pair with opposite spins was created coherently via the continuum states and that we can control the electron and nuclear spin polarizations only by changing the delay time of the cross-linearly-polarized pulses. These suggest the high potentiality of electron and nuclear spin manipulation in a single QD via the continuum state.

cond-mat.other↗

arXiv2005

Few-electron molecular states and their transitions in a single InAs quantum dot molecule

We study electronic configurations in a single pair of vertically coupled self-assembled InAs quantum dots, holding just a few electrons. By comparing the experimental data of non-linear single-electron transport spectra in a magnetic field with many-body calculations, we identify the spin and orbital configurations to confirm the formation of molecular states by filling both the quantum mechanically coupled symmetric and anti-symmetric states. Filling of the anti-symmetric states is less favored with increasing magnetic field, and this leads to various magnetic field induced transitions in the molecular states.

cond-mat.mes-hall↗

arXiv2004

Polarization-dependent shift in excitonic Zeeman splitting of self-assembled InAlAs quantum dots

We report the optical spectroscopic results of a single self-assembled InAlAs/Al GaAs quantum dot. The polarization-dependent shift of the Zeeman splitting in a single InAlAs QD has been observed. The induced Overhauser field is estimated to be 0.16 T in this InAlAs QD and the magnitude is shown to be controllable by the degree of circular polarization of excitation light.

cond-mat.other↗

arXiv2004

Single-dot spectroscopy via elastic single-electron tunneling through a pair of coupled quantum dots

We study the electronic structure of a single self-assembled InAs quantum dot by probing elastic single-electron tunneling through a single pair of weakly coupled dots. In the region below pinch-off voltage, the non-linear threshold voltage behavior provides electronic addition energies exactly as the linear, Coulomb blockade oscillation does. By analyzing it, we identify the s and p shell addition spectrum for up to six electrons in the single InAs dot, i.e. one of the coupled dots. The evolution of shell addition spectrum with magnetic field provides Fock-Darwin spectra of s and p shell.

cond-mat.mes-hall↗

arXiv2004

Molecular states observed in a single pair of strongly coupled self-assembled InAs quantum dots

Molecular states in a SINGLE PAIR of strongly coupled self-assembled InAs quantum dots are investigated using a sub-micron sized single electron transistor containing just a few pairs of coupled InAs dots embedded in a GaAs matrix. We observe a series of well-formed Coulomb diamonds with charging energy of less than 5 meV, which are much smaller than those reported previously. This is because electrons are occupied in molecular states, which are spread over both dots and occupy a large volume. In the measurement of ground and excited state single electron transport spectra with magnetic field, we find that the electrons are sequentially trapped in symmetric and anti-symmetric states. This result is well-explained by numerical calculation using an exact diagonalization method.

cond-mat.mes-hall↗