Structure-Assembly Relations in Viruses: From Density Waves to Spherical Crystallography

A variational theory is presented of A1− and A2− centers, i.e., of a negative acceptor ion localizing one and two conduction electrons, respectively, in a GaAs/GaAlAs quantum well in the presence of a magnetic field parallel to the growth direction. A combined effect of the well and magnetic field confines conduction electrons to the proximity of the ion, resulting in discrete repulsive energies above the corresponding Landau levels. The theory is motivated by our experimental magnetotransport results which indicate that, in a heterostructure doped in the GaAs well with Be acceptors, one observes a boil-off effect in which the conduction electrons in the crossed-field configuration are pushed by the Hall electric field from the delocalized Landau states to the localized acceptor states and cease to conduct. A detailed analysis of the transport data shows that, at high magnetic fields, there are almost no conducting electrons left in the sample. It is concluded that one negative acceptor ion localizes up to four conduction electrons.

We exploit the potential of the spin noise spectroscopy (SNS) for studies of nuclear spin dynamicsinn-GaAs. The SNS experiments were performed on bulkn-type GaAs layers embedded into ahigh-finesse microcavity at negative detuning. In our experiments, nuclear spin polarisation ini-tially prepared by optical pumping is monitored in real time via a shift of the peak position in theelectron spin noise spectrum. We demonstrate that this shift is a direct measure of the Overhauserfield acting on the electron spin. The dynamics of nuclear spin is shown to be strongly dependenton the electron concentration.

Indirect excitons in coupled quantum wells are long-living quasiparticles, explored in the studies of collective quantum states. We demonstrate that, despite the extremely low oscillator strength, their spin and population dynamics can by addressed by time-resolved pump-probe spectroscopy. Our experiments make it possible to unravel and compare spin dynamics of direct excitons, indirect excitons, and residual free electrons in coupled quantum wells. Measured spin relaxation time of indirect excitons exceeds not only one of direct excitons but also one of free electrons by two orders of magnitude.

This article introduces a stochastic thermodynamics for driven out-of-equilibrium open quantum systems. A stochastic Schrodinger equation allows to construct quantum trajectories describing the dynamics of the system state vector in presence of an environment. Thermodynamic quantities are then defined at the single quantum trajectory level. We thereby identify coherent contributions, without classical counterparts, leading to quantum fluctuations of thermodynamic quantities. This formalism eventually leads to central fluctuation theorems for entropy, extending in the quantum regime results obtained in classical stochastic thermodynamics. The thermal imprint of coherences on a simple implementation of Jarzynski equality is investigated, opening avenues for a thermodynamic approach to decoherence.