Tunneling spectra of layered strongly correlated d-wave superconductors

Tunneling conductance experiments on cuprate superconductors exhibit a large diversity of spectra that appear in different nano-sized regions of inhomogeneous samples. In this letter, we use a mean-field approach to the tt't''J model in order to address the features in these spectra that deviate from the BCS paradigm, namely, the bias sign asymmetry at high bias, the generic lack of evidence for the Van Hove singularity, and the occasional absence of coherence peaks. We conclude that these features can be reproduced in homogeneous layered d-wave superconductors solely due to a proximate Mott insulating transition. We also establish the connection between the above tunneling spectral features and the strong renormalization of the electron dispersion around (0,pi) and (pi,0) and the momentum space anisotropy of electronic states observed in ARPES experiments.Comment: 4 pages, 3 figures. Added comment on the role of sample inhomogeneity. Published version. Homepage http://dao.mit.edu/~wen

Sustainable forest management of miombo woodlands in Niassa National Reserve, northern Mozambique: a multidisciplinary approach of fire resistance analysis.

Poster presented at XIII World Forestry Congress. Buenos Aires (Argentina). 18 - 23 Oct 2009

Microstrip resonator for microwaves with controllable polarization

In this work the authors implemented a resonator based upon microstrip cavities that permits the generation of microwaves with arbitrary polarization. Design, simulation, and implementation of the resonators were performed using standard printed circuit boards. The electric field distribution was mapped using a scanning probe cavity perturbation technique. Electron spin resonance using a standard marker was carried out in order to verify the polarization control from linear to circular.Comment: 3 pages, 3 figures, submitted to Appl. Phys. Let

Nuclear State Preparation via Landau-Zener-Stueckelberg transitions in Double Quantum Dots

We theoretically model a nuclear-state preparation scheme that increases the coherence time of a two-spin qubit in a double quantum dot. The two-electron system is tuned repeatedly across a singlet-triplet level-anticrossing with alternating slow and rapid sweeps of an external bias voltage. Using a Landau-Zener-Stueckelberg model, we find that in addition to a small nuclear polarization that weakly affects the electron spin coherence, the slow sweeps are only partially adiabatic and lead to a weak nuclear spin measurement and a nuclear-state narrowing which prolongs the electron spin coherence. This resolves some open problems brought up by a recent experiment [D. J. Reilly et al., Science 321, 817 (2008).]. Based on our description of the weak measurement, we simulate a system with up to n=200 nuclear spins per dot. Scaling in n indicates a stronger effect for larger n.Comment: 4.1 pages, 2 figure