The complex relation between production and scattering amplitudes

The unitarity relation, Im(A)=T* A, is derived for a three-body production amplitude, A, that consists of a complex linear combination of elements of the two-body scattering amplitude, T. We conclude that the unitarity relation does not impose a realness condition on the coefficients in the expansion of, A, in terms of, T.Comment: 4 pages plain LaTe

Low temperature transport on surface conducting diamond

Magneto-transport measurements were performed on surface conducting hydrogen-terminated diamond (100) hall bars at temperatures between 0.1-5 K in magnetic fields up to 8T.Comment: 2 pages Optoelectronic and Microelectronic Materials & Devices (COMMAD), 2012 Conferenc

Single-shot readout of electron spin states in a quantum dot using spin-dependent tunnel rates

We present a method for reading out the spin state of electrons in a quantum dot that is robust against charge noise and can be used even when the electron temperature exceeds the energy splitting between the states. The spin states are first correlated to different charge states using a spin dependence of the tunnel rates. A subsequent fast measurement of the charge on the dot then reveals the original spin state. We experimentally demonstrate the method by performing read-out of the two-electron spin states, achieving a single-shot visibility of more than 80%. We find very long triplet-to-singlet relaxation times (up to several milliseconds), with a strong dependence on in-plane magnetic field.Comment: 4 pages, 4 figure

Semiconductor few-electron quantum dot operated as a bipolar spin filter

We study the spin states of a few-electron quantum dot defined in a two-dimensional electron gas, by applying a large in-plane magnetic field. We observe the Zeeman splitting of the two-electron spin triplet states. Also, the one-electron Zeeman splitting is clearly resolved at both the zero-to-one and the one-to-two electron transition. Since the spin of the electrons transmitted through the dot is opposite at these two transitions, this device can be employed as an electrically tunable, bipolar spin filter. Calculations and measurements show that higher-order tunnel processes and spin-orbit interaction have a negligible effect on the polarization.Comment: 4 pages, 3 figure

Control and Detection of Singlet-Triplet Mixing in a Random Nuclear Field

We observe mixing between two-electron singlet and triplet states in a double quantum dot, caused by interactions with nuclear spins in the host semiconductor. This mixing is suppressed by applying a small magnetic field, or by increasing the interdot tunnel coupling and thereby the singlet-triplet splitting. Electron transport involving transitions between triplets and singlets in turn polarizes the nuclei, resulting in striking bistabilities. We extract from the fluctuating nuclear field a limitation on the time-averaged spin coherence time T2* of 25 ns. Control of the electron-nuclear interaction will therefore be crucial for the coherent manipulation of individual electron spins.Comment: 4 pages main text, 4 figure

Mixing among light scalar mesons and L=1 q\bar{q} scalar mesons

Following the re-establishment of the \sigma(600) and the \kappa(900), the light scalar mesons a_0(980) and f_0(980) together with the \sigma(600) and the \kappa(900) are considered as the chiral scalar partner of pseudoscalar nonet in SU(3) chiral symmetry, and the high mass scalar mesons a_0(1450), K^*_0(1430), f_0(1370) and f_0(1710) turned out to be considered as the L=1 q\bar{q} scalar mesons. We assume that the high mass of the L=1 q\bar{q} scalar mesons is caused by the mixing with the light scalar mesons. For the structure of the light scalar mesons, we adopted the qq\bar{q}\bar{q} model in order to explain the "scalar meson puzzle". The inter-mixing between the light scalar nonet and the high mass L=1 q\bar{q} nonet and the intra-mixing among each nonet are analyzed by including the glueball into the high mass scalar nonet.Comment: 16 pages, 5 figure

Spin filling of a quantum dot derived from excited-state spectroscopy

We study the spin filling of a semiconductor quantum dot using excited-state spectroscopy in a strong magnetic field. The field is oriented in the plane of the two-dimensional electron gas in which the dot is electrostatically defined. By combining the observation of Zeeman splitting with our knowledge of the absolute number of electrons, we are able to determine the ground state spin configuration for one to five electrons occupying the dot. For four electrons, we find a ground state spin configuration with total spin S=1, in agreement with Hund's first rule. The electron g-factor is observed to be independent of magnetic field and electron number.Comment: 11 pages, 7 figures, submitted to New Journal of Physics, focus issue on Solid State Quantum Informatio

Cross-sectional association between metabolic parameters and psychotic-like experiences in a population-based sample of middle-aged and elderly individuals

Background: Metabolic alterations are often found in patients with clinical psychosis early in the course of the disorder. Psychotic-like experiences are observed in the general population, but it is unclear whether these are associated with markers of metabolism. Methods: A population-based cohort of 1890 individuals (mean age 58.0 years; 56.3% women) was included. Metabolic parameters were measured by body-mass index (BMI), concentrations of low-density and high-density lipoprotein cholesterol (LDL-C and HDL-C), total cholesterol, triglycerides, and fasting glucose and insulin in blood. Frequency and distress ratings of psychotic-like experiences from the positive symptom dimension of the Community Assessment of Psychic Experience questionnaire were assessed. Cross-sectional associations were analysed using linear regression analyses. Results: Higher BMI was associated with higher frequency of psychotic-like experiences (adjusted mean difference: 0.04, 95% CI 0.02–0.06) and more distress (adjusted mean difference: 0.02, 95% CI 0.01–0.03). Lower LDL-C was associated with more psychotic-like experiences (adjusted mean difference: −0.23, 95% CI −0.40 to −0.06). When restricting the sample to those not using lipid-lowering medication, the results of BMI and LDL-C remained and an association between lower HDL-C and higher frequency of psychotic-like experiences was found (adjusted mean difference: −0.37, 95% CI −0.69 to −0.05). We observed no significant associations between cholesterol, triglycerides, glucose, insulin or homeostatic model assessment and psychotic-like experiences. Conclusions: In a population-based sample of middle-aged and elderly individuals, higher BMI and lower LDL-C were associated with psychotic-like experiences. This suggests that metabolic markers are associated with psychotic-like experiences across the vulnerability spectrum.</p

Analysis of the vector meson transitions among the heavy quarkonium states

In this article, we study the vector meson transitions among the charmonium and bottomonium states with the heavy quark effective theory in an systematic way, and make predictions for the ratios among the vector meson decay widths of a special multiplet to another multiplet. The predictions can be confronted with the experimental data in the future.Comment: 14 pages, published versio