Dynamik von Quanten-Vielteilchensystemen. Equilibration, Thermalisierung und Typikalität in quanten-statistischer Mechanik

Balz BN. Dynamik von Quanten-Vielteilchensystemen. Equilibration, Thermalisierung und Typikalität in quanten-statistischer Mechanik. Bielefeld: Universität Bielefeld; 2018

Equilibration of isolated many-body quantum systems with respect to general distinguishability measures

Balz BN, Reimann P. Equilibration of isolated many-body quantum systems with respect to general distinguishability measures. PHYSICAL REVIEW E. 2016;93(6): 62107.We demonstrate equilibration of isolated many-body systems in the sense that, after initial transients have died out, the system behaves practically indistinguishable from a time-independent steady state, i.e., non-negligible deviations are unimaginably rare in time. Measuring the distinguishability in terms of quantum mechanical expectation values, results of this type have been previously established under increasingly weak assumptions about the initial disequilibrium, the many-body Hamiltonian, and the considered observables. Here, we further extend these results with respect to generalized distinguishability measures which fully take into account the fact that the actually observed, primary data are not expectation values but rather the probabilistic occurrence of different possible measurement outcomes

Typical Relaxation of Isolated Many-Body Systems Which Do Not Thermalize

Balz BN, Reimann P. Typical Relaxation of Isolated Many-Body Systems Which Do Not Thermalize. PHYSICAL REVIEW LETTERS. 2017;118(19): 190601.We consider isolated many-body quantum systems which do not thermalize; i.e., expectation values approach an (approximately) steady longtime limit which disagrees with the microcanonical prediction of equilibrium statistical mechanics. A general analytical theory is worked out for the typical temporal relaxation behavior in such cases. The main prerequisites are initial conditions which appreciably populate many energy levels and do not give rise to significant spatial inhomogeneities on macroscopic scales. The theory explains very well the experimental and numerical findings in a trapped-ion quantum simulator exhibiting many-body localization, in ultracold atomic gases, and in integrable hard-core boson and XXZ models

Hydrophobicity-driven self-assembly of protein and silver nanoparticles for protein detection using surface-enhanced Raman scattering

Kahraman M, Balz BN, Wachsmann-Hogiu S. Hydrophobicity-driven self-assembly of protein and silver nanoparticles for protein detection using surface-enhanced Raman scattering. The Analyst. 2013;138(10):2906-2913.Surface-enhanced Raman scattering (SERS) is a promising analytical technique for the detection and characterization of biological molecules and structures. The role of hydrophobic and hydrophilic surfaces in the self-assembly of protein-metallic nanoparticle structures for label-free protein detection is demonstrated. Aggregation is driven by both the hydrophobicity of the surface as well as the charge of the proteins. The best conditions for obtaining a reproducible SERS signal that allows for sensitive, label-free protein detection are provided by the use of hydrophobic surfaces and 16 x 10(11) NPs per mL. A detection limit of approximately 0.5 mu g mL(-1) is achieved regardless of the proteins' charge properties and size. The developed method is simple and can be used for reproducible and sensitive detection and characterization of a wide variety of biological molecules and various structures with different sizes and charge status

Temporal relaxation of gapped many-body quantum systems

Reimann P, Balz BN, Richter J, Steinigeweg R. Temporal relaxation of gapped many-body quantum systems. PHYSICAL REVIEW B. 2020;101(9): 094302.Typicality of the orthogonal dynamics (TOD) is established as a generic feature of the temporal relaxation processes in isolated many-body quantum systems. The basic idea in the simplest case is that the transient nonequilibrium behavior is mainly governed by the component of the time-evolved system state parallel to the initial state, while the orthogonal component appears as equilibrated right from the beginning. The main emphasis is laid on the largely unexplored and particularly challenging case that one energy level exhibits a much larger population than all the others. Important examples are gapped many-body systems at low energies, for instance, due to a quantum quench. A general analytical prediction is derived and is found to compare very well with various numerically exact results