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.Comment: 7 pages, 3 figures, Accepted for publication in Phys. Rev. Let

Short timescale behavior of colliding heavy nuclei at intermediate energies

An Antisymmetrized Molecular Dynamics model is used to explore the collision of $^{114}$Cd projectiles with $^{92}$Mo target nuclei at E/A=50 MeV over a broad range in impact parameter. The atomic number (Z), velocity, and emission pattern of the reaction products are examined as a function of the impact parameter and the cluster recognition time. The non-central collisions are found to be essentially binary in character resulting in the formation of an excited projectile-like fragment (PLF$^*$) and target-like fragment (TLF$^*$). The decay of these fragments occurs on a short timescale, 100$\le$t$\le$300 fm/c. The average excitation energy deduced for the PLF$^*$ and TLF$^*$ `saturates for mid-central collisions, 3.5$\le$b$\le$6 fm, with its magnitude depending on the cluster recognition time. For short cluster recognition times (t=150 fm/c), an average excitation energy as high as $\approx$6 MeV is predicted. Short timescale emission leads to a loss of initial correlations and results in features such as an anisotropic emission pattern of both IMFs and alpha particles emitted from the PLF$^*$ and TLF$^*$ in peripheral collisions.Comment: 19 pages, 17 figure

Electrochemical synthesis and properties of CoO2, the x = 0 phase of the AxCoO2 systems (A = Li, Na)

Single-phase bulk samples of the "exotic" CoO2, the x = 0 phase of the AxCoO2 systems (A = Li, Na), were successfully synthesized through electrochemical de-intercalation of Li from pristine LiCoO2 samples. The samples of pure CoO2 were found to be essentially oxygen stoichiometric and possess a hexagonal structure consisting of stacked triangular-lattice CoO2 layers only. The magnetism of CoO2 is featured with a temperature-independent susceptibility of the magnitude of 10-3 emu/mol Oe, being essentially identical to that of a Li-doped phase, Li0.12CoO2. It is most likely that the CoO2 phase is a Pauli-paramagnetic metal with itinerant electrons.Comment: 12 pages, 3 figure

First-principles study on field evaporation for silicon atom on Si(001) surface

The simulations of field-evaporation processes for silicon atoms on various Si(001) surfaces are implemented using the first-principles calculations based on the real-space finite-difference method. We find that the atoms which locate on atomically flat Si(001) surfaces and at step edges are easily removed by applying external electric field, and the threshold value of the external electric field for evaporation of atoms on atomically flat Si(001) surfaces, which is predicted between 3.0 and 3.5 V/\AA, is in agreement with the experimental data of 3.8 V/\AA. In this situation, the local field around an evaporating atom does not play a crucial role. This result is instead interpreted in terms of the bond strength between an evaporating atom and surface.Comment: 5 pages and 4 figure