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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Heat-flux control and solid-state cooling by regulating chemical potential of photons in near-field electromagnetic heat transfer

We consider near-field heat transfer with nonzero chemical potential for photons, as can occur between two semiconductor bodies, held at different temperatures with at least one of the bodies under external bias.We show that the dependence of radiative heat flux on chemical potential enables electronic control of both the direction and magnitude of near-field heat transfer between the two bodies. Moreover such a configuration can operate as a solid-state cooling device whose efficiency can approach the Carnot limit in the ideal case. Furthermore, significant cooling can also be achieved in the presence of inherent nonidealities including Auger recombination and parasitic phonon-polariton heat transfer.

42 ENGINEERING↗
DOE OSTI2017

Particle-hole symmetry and electromagnetic response of a half-filled Landau level

We derive exact physical consequences of particle-hole symmetry of the ν = 1/2 state of electrons in a strong magnetic field. We show that if the symmetry is not spontaneously broken, the Hall conductivity and the susceptibility satisfy an exact relationship, valid at any wave numbers and any frequencies much below the cyclotron frequency. The relationship holds for clean systems and also for systems with statistically particle-hole symmetric disorder. We work out the constraints this relationship imposes on the theory of the Dirac composite fermion. Here, we also argue that that the exact relationship is violated in the Halperin-Lee-Read (HLR) field theory and present an explicit calculation within a Galilean invariant mean-field approximation to the HLR theory to illustrate the breakdown.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Study of electromagnetic Dalitz decays χ c J → μ + μ - J / ψ

Using 4.48 × 10 8 ψ (3686) events collected with the BESIII detector, we search for the decays χ cJ → μ + μ – J/ψ through the radiative decays ψ(3686) → γχ cJ , where J = 0,1,2. The decays χ c1,2 → μ + μ – J/ψ are observed, and the corresponding branching fractions are measured to be B(χ c1 → μ + μ – J/ψ) = (2.51 ± 0.18 ± 0.20) × 10 –4 and B(χ c2 → μ + μ – J/ψ) = (2.33 ± 0.18 ± 0.29) × 10 –4 , where the first uncertainty is statistical and the second one systematic. No significant χ c0 → μ + μ – J/ψ decay is observed, and the upper limit on the branching fraction is determined to be 2.0×10 –5 at 90% confidence level. Furthermore, we present a study of dimuon invariant mass dependent transition form factor for the decays χ c1,2 → μ + μ – J/ψ.

astronomy & astrophysics↗