 Publication Date:
 NSFPAR ID:
 10342477
 Journal Name:
 Journal of High Energy Physics
 Volume:
 2021
 Issue:
 7
 ISSN:
 10298479
 Sponsoring Org:
 National Science Foundation
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Resonant tunneling diodes (RTDs) have come fullcircle in the past 10 years after their demonstration in the early 1990s as the fastest roomtemperature semiconductor oscillator, displaying experimental results up to 712 GHz and fmax values exceeding 1.0 THz [1]. Now the RTD is once again the preeminent electronic oscillator above 1.0 THz and is being implemented as a coherent source [2] and a selfoscillating mixer [3], amongst other applications. This paper concerns RTD electroluminescence – an effect that has been studied very little in the past 30+ years of RTD development, and not at room temperature. We present experiments and modeling of an ntype In0.53Ga0.47As/AlAs doublebarrier RTD operating as a crossgap light emitter at ~300K. The MBEgrowth stack is shown in Fig. 1(a). A 15μmdiammesa device was defined by standard planar processing including a top annular ohmic contact with a 5μmdiam pinhole in the center to couple out enough of the internal emission for accurate freespace power measurements [4]. The emission spectra have the behavior displayed in Fig. 1(b), parameterized by bias voltage (VB). The long wavelength emission edge is at = 1684 nm  close to the In0.53Ga0.47As bandgap energy of Ug ≈ 0.75 eV at 300 K.more »

Abstract It is one of the biggest issues in black hole (BH) astrophysics how to evaluate BH feedback to its environments precisely. Aiming at studying the unique gas dynamics of superEddington flow around supermassive black hole (SMBH) seeds at high redshift, we carried out axisymmetric twodimensional radiation hydrodynamic simulations using a nested simulationbox method. Here we divide the simulation box into an inner zone at (2–3 × 103)rSch (with rSch being the Schwarzschild radius) and an outer zone at (2 × 103–3 × 106)rSch, with smooth connection of the physical quantities, such as gas density, velocity, and radiation energy. We start the calculation by injecting mass through the outer boundary of the inner zone at a constant rate of $\dot{M}_{\rm {inj}}=10^3L_{\rm {Edd}}/c^2$, where LEdd is the Eddington luminosity and c is the speed of light. A powerful outflow is generated in the innermost region and it propagates from the inner zone to the outer zone. The outflows are characterized by a velocity of 0.02c (0.7c) and density of 10−17 (10−19) g cm−3 for near the edgeon (faceon) direction. The outflow is gradually accelerated as it travels by accepting radiationpressure force. The final mass outflow rate at the outermost boundary is $\dot{M}_{\rm {out}}\simmore »

ABSTRACT Direct collapse black holes (BHs) are promising candidates for producing massive z ≳ 6 quasars, but their formation requires finetuned conditions. In this work, we use cosmological zoom simulations to study systematically the impact of requiring: (1) low gas angular momentum (spin), and (2) a minimum incident Lyman–Werner (LW) flux in order to form BH seeds. We probe the formation of seeds (with initial masses of $M_{\rm seed} \sim 10^4\!\!10^6\, \mathrm{M}_{\odot }\, h^{1})$ in haloes with a total mass >3000 × Mseed and a dense, metalpoor gas mass >5 × Mseed. Within this framework, we find that the seedforming haloes have a prior history of star formation and metal enrichment, but they also contain pockets of dense, metalpoor gas. When seeding is further restricted to haloes with low gas spins, the number of seeds formed is suppressed by factors of ∼6 compared to the baseline model, regardless of the seed mass. Seed formation is much more strongly impacted if the dense, metalpoor gas is required to have a critical LW flux (Jcrit). Even for Jcrit values as low as 50J21, no $8\times 10^{5}~\mathrm{M}_{\odot }\, h^{1}$ seeds are formed. While lower mass ($1.25\times 10^{4},1\times 10^{5}~\mathrm{M}_{\odot }\, h^{1}$) seeds do form, they are strongly suppressed (by factors of ∼10–100) comparedmore »

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