The dynamics of doping transformation fronts in organic semiconductor plasma is studied for application in light-emitting electrochemical cells. We show that new fundamental effects of the plasma dynamics can significantly improve the device performance. We obtain an electrodynamic instability, which distorts the doping fronts and increases the transformation rate considerably. We explain the physical mechanism of the instability, develop theory, provide experimental evidence, perform numerical simulations, and demonstrate how the instability strength may be amplified technologically. The electrodynamic plasma instability obtained also shows interesting similarity to the hydrodynamic Darrieus-Landau instability in combustion, laser ablation, and astrophysics.

We develop a model describing the electrochemical conversion of an organic semiconductor (specifically, the active material in a light-emitting electrochemical cell) from the undoped non-conducting state to the doped conducting state. The model takes into account both strongly concentrationdependent mobility and diffusion for the electronic charge carriers and the Nernst equation in the doped conducting regions. It is demonstrated that the experimentally observed doping front progression in light-emitting electrochemical cells can be accurately described with this model.

Recent experiments [W. Decelle et al., Phys. Rev. Lett. 102, 027203 (2009)] have discovered ultrafast propagation of spin avalanches in crystals of nanomagnets, which is 3 orders of magnitude faster than the traditionally studied magnetic deflagration. The new regime has been hypothetically identified as magnetic detonation. Here we demonstrate unequivocally the possibility of magnetic detonation in the crystals, as a front consisting of a leading shock and a zone of Zeeman energy release. We study the key features of the process and find that the magnetic detonation speed only slightly exceeds the sound speed in agreement with the experimental observations. For combustion science, our results provide a unique physical example of extremely weak detonation.

The stability of a magnetic deflagration front in a collection of molecular magnets, such as Mn 12 -acetate, is considered. It is demonstrated that stationary deflagration is unstable with respect to one-dimensional perturbations if the energy barrier of the magnets is sufficiently high in comparison with the release of Zeeman energy at the front; their ratio may be interpreted as an analogue to the Zeldovich number, as found in problems of combustion. When the Zeldovich number exceeds a certain critical value, a stationary deflagration front becomes unstable and propagates in a pulsating regime. Analytical estimates for the critical Zeldovich number are obtained. The linear stage of the instability is investigated numerically by solving the eigenvalue problem. The nonlinear stage is studied using direct numerical simulations. The parameter domain required for experimental observations of the pulsating regime is discussed.

Influence of quantum effects on the internal waves and the Rayleigh-Taylor instability in plasma is investigated. It is shown that quantum pressure always stabilizes the RT instability. The problem is solved both in the limit of short-wavelength perturbations and exactly for density profiles with layers of exponential stratification.In the case of stable stratification, quantum pressure modifies the dispersion relation of the inertial waves. Because of the quantum effects, the internal waves may propagate in the transverse direction, which was impossible in the classical case. A specific form of pure quantum internal waves is obtained, which do not require any external gravitational field. Studies of quantum plasmas was initiated byPines in the 1960's [1, 2], where the finite width of the electron wave function gives rise to dispersion, important in the high-density and/or low temperature regime. A number of quantum plasma studies has since appeared Ref. [3], e.g., kinetic models of the quantum electrodynamical properties of nonthermal plasmas [4] and covariant Wigner function descriptions of relativistic quantum plasmas [5]. There has recently been a surge in the interest of quantum plasmas, see e.g. Refs.[ 6,7,8,9,10,11,12,13], in particular the nonlinear properties of dense [14,15,16] or magnetized plasmas [13,17,18]. Many of these studies have motivated by new discoveries concerning nanostructured materials [19] and quantum wells [20], the discovery of ultracold plasmas [21,22,23], astrophysical applications [24], and inertial fusion plasmas [25]. For such quantum systems, the so called Bohm-de Broglie potential [6,7,8,9,10], as well as the zero temperature Fermi pressure [6,7,8,9,10] and other spin properties [11,12,13,17,18] can significantly modify the dynamics of the plasma. Moreover, quantum electrodynamical effects can give rise to completely new effects in plasma environments [26,27,28,29] that can be of relevance in high-intensity quantum plasmas. Within the fluid approach to quantum plasmas [6,7,8,9,10,11,12,27,28,29], collective effects can be described within a