The dependence of two-particle energies on plasma density is investigated using Green's functions. An effective exciton equation is derived taking into account dynamically screened potential and one-particle self-energies. A variational calculation shows that the bound state levels (exciton energies) remain practically constant whereas the continuum edge (band gap) shifts to lower energies with increasing density, which is in accordance with experimental observations. Die Abhiingigkeit der Zwei-Teilchen-Energien von der Plasmadichte wird im Formalismus Greenscher Funktionen untersucht. Es wird eine effektive Exziton-Gleichung abgeleitet, die ein dynamisch abgeschirmtes Potential und Ein-Teilchen-Selbstenergien beriicksichtigt. Eine Variationsrechuung zeigt, deD Energieniveaus gebundener Zustiinde (Exzitonenenergien) praktisch konstant bleiben, wiihrend sich die Kontinuumskante (die Bandliicke) mit wachsender Dichte zu kleineren Energien verschiebt, was mit experimentellen Ergebnissen ubereinstimmt.
The electrical conductivity of fully ionized, nondegenerate hydrogen plasma is expressed within the Zubarev method by equilibrium correlation functions. Using the Green’s function technique, the Lenard–Balescu–Gurnsey collision integral of a generalized Boltzmann equation is derived that accounts for the effects of dynamic screening. Applying the usual random phase approximation, numerical results for the collision integral and the electrical conductivity are compared with the case of static screening (ω=0) and the long-wavelength limit (q→0) for the dielectric function Ε(q,ω). Effective low-density expansions are given for the collision integrals as well as for the electrical conductivity that are applicable for a wide range of density and temperature.
Thermodynamic functions of an electron-hole plasma in an optically excited semiconductor are derived in the nondegenerate region. The existence of excitons and the ionization equilibrium are discussed in the me-T (electron density-temperature) plane. Above the Mott curve (r, = 0.84 a,, r, screening length, a, Bohr's radius) excitons do not exist. Besides the well known electron-hole droplet phase transition the critical point of which lies above the Mott curve, a region of instability is found below the Mott curve which might correspond t o a plasma phase transition (weakly ionized plasma -+ strongly ionized plasma). Outside of this instability region a t the Mott curve a diffuse phase transition (Mott-transition) exists.Es werden thermodynamische Bunktionen fur ein Elektron-Loch-Plasma in einem optisch angeregten IIalbleiter fur den nichtentarteten Fall berechnet. Die Bildung von Exzitonen und das Ioriisationsgleichgewicht werden in der ne-T (Elektronendichte-Temperatur)-Ebene diskutiert. Oberhalb der Mott-Kurve (yo = 0.84 a,, r, Abschirmlange, a, Bohrscher Radius) existieren keine Exzitonen. AuDer dem bekannten Elektronen-Loch-TropfenPhasenubergang, dessen kritischer Punkt oberhalb der Mott-Kurve liegt, findet man ein Instabilitatsgebiet unterhalb der Mott-Kurve, welches moglicherweise einem Plasma-Phaseniibergang entsprioht (schwach ionisiertes Plasma + stark ionisiertes Plasma). AuBerhalb dieses Instabilitlitsgebietes findet man an der Mott-Geraden einen diffusen Phasenubergang (Mott -Uberg ang ).
Variations of the spectral lines in high dense ion plasmas with temperature and pressure may be characterized by the broadening aa well as by t@ shift of spectral lines. For dense hydrogen-and alkali-plasmas (free carrier density larger than lW$3m3) one of the possible mechankms responsible for line profiles is considered to be the Coulomb interaction with free charged mrriers. Using thermodynamic Green's functions, a systematic approach to the theory of spectral lines starting from the complex dielectric function is outlined. "he line shift is derived from a perturbiltive treatment of the two-particle Green's function in the sufrounding plasma. The shift of several lines proportional to the carrier density is evaluated as a function of the temperature and compared with experimental results.Inhaltsiibersicht. Bnderungen im Linienspektrum hochdichter Ionenplasmen mit Temperatur und Druck konnen durch eine Verbreitemg sowie durch eine Verschiebung der Spektrallinien beschrieben werden. Fiir dichte Wasserstoff-und Alkaliplasmen (Dichte der freien Ladungstriiger g r o h r als 1016/cms) wird als ein moglicher Mechanismus fiir die hderung im Linienprofil die Coulombwechselwirkung mit freien Ladungstriigern betrachtet. Ein systematischer Zugang zur Theorie von Spektrallinien ausgehend von der komplexen dielektrischen Funktion und unter Verwendung thermcdynamischer Greenscher Funktionen wird benutzt. Die Linienverschiebung wird aus einer stijrungstheoretischen Behandlung der Qreenschen Funktion zweier Teilchen in einem Plasma abgeleitet. Die Verschiebung verschiedener Spektrallinien, die proportional zur Dichte der freien Ladungstriiger ist, wird in Abhiingigkeit von der Temperatur ausgewertet und mit experimentellen Werten verglichen.
In a plasma (electrons and holes, ab = eh, or electrons and protons, a b = ep, density n = n = n) the two-particle energies a r e influenced by the interaction with a b the plasma which results in a shift of the energy levels and a finite life time. In detail, the plasma gives rise to a change of single particle energies and to a dynamical screening of the Coulomb interaction between the particles. Recently, the influence of the dynamical screening on the complex two-particle energies (excitons) was investigated /1, 2/. The a i m of the present work is to take into account the selfenergy effects in a consistent way.We start with the following Bethe-Salpeter equation (BSE) /1, 3/ for the twoparticle Green's function f o r different species a ,,b: r a a b with Matsubara frequencies fizV =~cv/(-iB) + pa( Y odd) and%Qh =rA/(-if3) + pa + pb ( h even). The dynamica!ly screened Coulomb potential is given by V (q,sZ ) = =V(q)/r(q,sZ ), V(q) = 4 x e / Eoq , Green's functionG is connected to the self-energy (mass operator) c by Dyson's equation S 2 2 E ( q , n ) dielectric function. The one-particle a a -1 a a 2 aGa (p, z ) =ii z -P /21na -C, (P, zv) .
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