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Register a new userTheoretical foundations of quantum hydrodynamics for plasmas
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Beginning from the semiclassical Hamiltonian, the Fermi pressure and Bohm potential for the quantum hydrodynamics application (QHD) at finite temperature are consistently derived in the framework of the local density approximation with the first order density gradient correction. Previously known results are revised and improved with a clear description of the underlying approximations. A fully non-local Bohm potential, which goes beyond of all previous results and is linked to the electron polarization function in the random phase approximation, for the QHD model is presented. The dynamic QHD exchange correlation potential is introduced in the framework of local field corrections, and considered for the case of the relaxation time approximation. Finally, the range of applicability of the QHD is discussed.
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This thesis investigates geometric approaches to quantum hydrodynamics (QHD) in order to develop applications in theoretical quantum chemistry. Based upon the momentum map geometric structure of QHD and the associated Lie-Poisson and Euler-Poincare equations, alternative geometric approaches to the classical limit in QHD are presented. These include a new regularised Lagrangian which allows for singular solutions called Bohmions as well as a cold fluid classical closure quantum mixed states. The momentum map approach to QHD is then applied to the nuclear dynamics in a chemistry model known as exact factorization. The geometric treatment extends existing approaches to include unitary electronic evolution in the frame of the nuclear flow, with the resulting dynamics carrying both Euler-Poincare and Lie-Poisson structures. A new mixed quantum-classical model is then derived by considering a generalised factorisation ansatz at the level of the molecular density matrix. A new alternative geometric formulation of QHD is then constructed. Introducing a $mathfrak{u}(1)$ connection as the new fundamental variable provides a new method for incorporating holonomy in QHD, which follows from its constant non-zero curvature. The fluid flow is no longer irrotational and carries a non-trivial circulation theorem, allowing for vortex filament solutions. Finally, non-Abelian connections are then considered in quantum mechanics. The dynamics of the spin vector in the Pauli equation allows for the introduction of an $mathfrak{so}(3)$ connection whilst a more general $mathfrak{u}(mathscr{H})$ connection is introduced from the unitary evolution of a quantum system. This is used to provide a new geometric picture for the Berry connection and quantum geometric tensor, whilst relevant applications to quantum chemistry are then considered.
Surface plasmons (SP) in a semi-bounded quantum plasma with degenerate electrons (e.g., a metal) is considered, and some interesting consequences of electron Pauli blocking for the SP dispersion and temporal attenuation are discussed. In particular, it is demonstrated that a semi-bounded degenerate plasma with a sharp boundary supports two types of SP with distinct frequencies and qualitatively different temporal attenuation, in contrast to a non-degenerate plasma that only supports one type of SP citep{Guernsey_1969}.
We report a theoretical equation of state (EOS) table for boron across a wide range of temperatures (5.1$times$10$^4$-5.2$times$10$^8$ K) and densities (0.25-49 g/cm$^3$), and experimental shock Hugoniot data at unprecedented high pressures (5608$pm$118 GPa). The calculations are performed with full, first-principles methods combining path integral Monte Carlo (PIMC) at high temperatures and density functional theory molecular dynamics (DFT-MD) methods at lower temperatures. PIMC and DFT-MD cross-validate each other by providing coherent EOS (difference $<$1.5 Hartree/boron in energy and $<$5% in pressure) at 5.1$times$10$^5$ K. The Hugoniot measurement is conducted at the National Ignition Facility using a planar shock platform. The pressure-density relation found in our shock experiment is on top of the shock Hugoniot profile predicted with our first-principles EOS and a semi-empirical EOS table (LEOS 50). We investigate the self diffusivity and the effect of thermal and pressure-driven ionization on the EOS and shock compression behavior in high pressure and temperature conditions We study the performance sensitivity of a polar direct-drive exploding pusher platform to pressure variations based on comparison of the first-principles calculations with LEOS 50 via 1D hydrodynamic simulations. The results are valuable for future theoretical and experimental studies and engineering design in high energy density research. (LLNL-JRNL-748227)
Semiconductor devices are strong competitors in the race for the development of quantum com-putational systems. In this work, we interface two semiconductor building blocks of different di-mensionality and with complementary properties: (1) a quantum dot hosting a single exciton andacting as a nearly ideal single-photon emitter and (2) a quantum well in a 2D microcavity sustain-ing polaritons, which are known for their strong interactions and unique hydrodynamics propertiesincluding ultrafast real-time monitoring of their propagation and phase-mapping. In the presentexperiment we can thus observe how the injected single particles propagate and evolve inside themicrocavity, giving rise to hydrodynamics features typical of macroscopic systems despite their in-trinsic genuine quantum nature. In the presence of a structural defect, we observe the celebratedquantum interference of a single particle that produces fringes reminiscent of a wave propagation.While this behaviour could be theoretically expected, our imaging of such an interference pattern,together with a measurement of antibunching, constitutes the first demonstration of spatial mappingof the self-interference of a single quantum particle hitting an obstacle.
We study the underlying theory of dielectric haloscopes, a new way to detect dark matter axions. When an interface between different dielectric media is inside a magnetic field, the oscillating axion field acts as a source of electromagnetic waves, which emerge in both directions perpendicular to the surface. The emission rate can be boosted by multiple layers judiciously placed to achieve constructive interference and by a large transverse area. Starting from the axion-modified Maxwell equations, we calculate the efficiency of this new dielectric haloscope approach. This technique could potentially search the unexplored high-frequency range of 10--100 GHz (axion mass 40--400 $mu$eV), where traditional cavity resonators have difficulties reaching the required volume.
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