Area dependence of interlayer tunneling in strongly correlated bilayer two-dimensional electron systems at ν_T = 1

The area and perimeter dependence of the Josephson-like interlayer tunneling signature of the coherent ν_T = 1 quantum Hall phase in bilayer two-dimensional electron systems is examined. Electrostatic top gates of various sizes and shapes are used to locally define distinct ν_T = 1 regions in the same sample. Near the phase boundary with the incoherent ν_T = 1 state at large layer separation, our results demonstrate that the tunneling conductance in the coherent phase is closely proportional to the total area of the tunneling region. This implies that tunneling at ν_T = 1 is a bulk phenomenon in this regime

Charge Imbalance and Bilayer 2D Electron Systems at νT=1\nu_T = 1

We use interlayer tunneling to study bilayer 2D electron systems at $\nu_T = 1$ over a wide range of charge density imbalance, $\Delta \nu =\nu_1-\nu_2$, between the two layers. We find that the strongly enhanced tunneling associated with the coherent excitonic $\nu_T = 1$ phase at small layer separation can survive at least up to an imbalance of $\Delta \nu$ = 0.5, i.e $(\nu_1, \nu_2)$ = (3/4, 1/4). Phase transitions between the excitonic $\nu_T = 1$ state and bilayer states which lack significant interlayer correlations can be induced in three different ways: by increasing the effective interlayer spacing $d/\ell$, the temperature $T$, or the charge imbalance, $\Delta \nu$. We observe that close to the phase boundary the coherent $\nu_T = 1$ phase can be absent at $\Delta \nu$ = 0, present at intermediate $\Delta \nu$, but then absent again at large $\Delta \nu$, thus indicating an intricate phase competition between it and incoherent quasi-independent layer states. At zero imbalance, the critical $d/\ell$ shifts linearly with temperature, while at $\Delta \nu$ = 1/3 the critical $d/\ell$ is only weakly dependent on $T$. At $\Delta \nu$ = 1/3 we report the first observation of a direct phase transition between the coherent excitonic $\nu_T = 1$ bilayer integer quantum Hall phase and the pair of single layer fractional quantized Hall states at $\nu_1$ = 2/3 and $\nu_2=1/3$.Comment: 13 pages, 8 postscript figures. Final published versio

The reactions and ashes of thermonuclear explosions on neutron stars

This paper reports on the detailed rp-process reaction flow on an accreting neutron star and the resulting ashes of a type I X-ray burst. It is obtained by coupling a 298 isotope reaction network to a self-consistent one-dimensional model calculation with a constant accretion rate of dM/dt=1.0e17g/s (0.09 Eddington).Comment: 4 pages, 2 figures, submitted to the INPC2004 proceeding

Second-Order Nonlinear Optical Properties of Multiaddressable Indolinooxazolidine Derivatives: Joint Computational and Hyper-Rayleigh Scattering Investigations

The linear and nonlinear optical (NLO) properties of two indolinooxazolidine derivatives acting as multiaddressable switches are reported. The second-order hyperpolarizability contrasts upon commutation between their closed and open forms are characterized using hyper-Rayleigh scattering (HRS) measurements, and rationalized by means of density functional theory and post Hartree–Fock ab initio calculations. It is evidenced that the addition of a withdrawing substituent on the indolinic subunit leads to a more effective photoinduced charge transfer while decreasing the transition energy of the S0 → S1 transition, which induces a significant enhancement of the HRS response of the open form. This substitution is however detrimental to the NLO contrast, due to the concomitant increase of the HRS response of the closed form

Development and Characterisation of a Gas System and its Associated Slow-Control System for an ATLAS Small-Strip Thin Gap Chamber Testing Facility

A quality assurance and performance qualification laboratory was built at McGill University for the Canadian-made small-strip Thin Gap Chamber (sTGC) muon detectors produced for the 2019-2020 ATLAS experiment muon spectrometer upgrade. The facility uses cosmic rays as a muon source to ionise the quenching gas mixture of pentane and carbon dioxide flowing through the sTGC detector. A gas system was developed and characterised for this purpose, with a simple and efficient gas condenser design utilizing a Peltier thermoelectric cooler (TEC). The gas system was tested to provide the desired 45 vol% pentane concentration. For continuous operations, a state-machine system was implemented with alerting and remote monitoring features to run all cosmic-ray data-acquisition associated slow-control systems, such as high/low voltage, gas system and environmental monitoring, in a safe and continuous mode, even in the absence of an operator.Comment: 23 pages, LaTeX, 14 figures, 4 tables, proof corrections for Journal of Instrumentation (JINST), including corrected Fig. 8b