Veranstaltungsarchiv 2016

Hier finden Sie vergangene Veranstaltungen des MPSDs und der MPSD-Forschungsgruppen an der Universität Hamburg.

Disputation

7862 1480927714

Wei Liu - Advanced ultrafast fiber laser sources enabled by fiber nonlinearities

[mehr]

IMPRS-UFAST skills course

7691 1480511990

Presentation skills

“Poets are born – speakers are made.” Public speaking is a necessity in scientific life. Take part in this two-days course, find out what your strengths are and develop your individual presentation profile. Take steps to learn how to lead the audience from your first appearance on stage until the last question in the discussion. Be authentic, enthusiastic and convincing! [mehr]

MPSD Seminar

7526 1477570339

Designer nanostructures for visible light

There exists a size difference between molecules and visible wavelengths. Nanofabrication techniques can be adopted to obtain designed meta-molecules or meta-materials, with interesting optical properties. [mehr]

MPSD Seminar

6712 1474980087

Ultracold Fermions in Optical Lattices as a Testbed for Dynamically Driven Complex Materials

Complex quantum many-body systems are ubiquitous in nature, but their behaviour often remains very challenging to predict with analytical or numerical calculations - especially when it comes to dynamics. However, using ultracold atoms in optical lattices it is possible to create precisely tunable, yet very accessible artificial solids, which can be probed with a large arsenal of observables. Using this experimental set-up, we demonstrate how a periodically modulated lattice can be described by an effective Floquet-Hamiltonian on longer time scales - even when driving the system far from equilibrium. This allows for implementing Haldane's model for a topological insulator, and mapping out its topological transitions, by applying an oscillating force to a honeycomb lattice. Using an oscillating magnetic field gradient, we also engineer spin-dependent bands. By adding interactions to the optical lattice system, we create a pure realisation of the Hubbard model and study how the distribution of anti-ferromagnetic correlations therein depends on the geometry of the lattice. We investigate how fast correlations can re-arrange, by deforming the lattice geometry on time-scales ranging from the sudden to the adiabatic regime. Finally, we explore how an oscillating force applied to this interacting system may be used to tune and enhance the magnetic exchange energy beyond the regimes accessible within the Hubbard model. [mehr]

MPSD Seminar

6692 1474640231

Dynamical phase transitions in the long-range (powerlaw) interacting transverse-field Ising model

Dynamical phase transitions (DPTs) have gained a lot of interest in the past few years in a variety of quantum many-body systems, where a system in its groundstate is quenched by abruptly changing a control parameter of the Hamiltonian, such as interaction strength or external field. Afterwards, a DPT can be detected in one of at least two forms: a type-I DPT which is detected, after relaxation in time, through the nonanalyticity of an appropriate order parameter as a function of the control parameter through which the quench is effected; and a type-II DPT which is detected as a nonanalyticity of the Loschmidt echo return rate as a function in time, without giving care as to whether or not a stationary state has been reached in the time evolution. [mehr]

MPSD Seminar

6278 1470062336

Light induced enhancement of superconductivity via melting of competing bond-density wave order in underdoped cuprates

We develop a theory for light-induced superconductivity in underdoped cuprates in which the competing bond-density wave order is suppressed by driving phonons with light. Close to a bond-density wave instability in a system with a small Fermi surface, such as a fractionalized Fermi liquid, we show that the coupling of electrons to phonons is strongly enhanced at the bond-density wave ordering wavevectors, leading to a strong softening of phonons at these wavevectors. For a model of classical phonons with anharmonic couplings, we show that thecombination of strong softening and driving can lead to large phonon oscillations. When coupled to a phenomenological model describing the competition between bond-density wave order and superconductivity, these phonon oscillations melt bond-density wave order, thereby enhancing pairing correlations. [mehr]

Disputation

5880 1480499955

Generation and control of super-octave-spanning spectra

[mehr]

CFEL Theory Seminar

5927 1466690975

Nonequilibrium dynamics of strongly coupled phonon-mediated superconductors

Recent developments in ultra-fast laser techniques allow experimentalists to reveal intriguing aspects of the dynamics of superconductors such as the Higgs oscillations (amplitude oscillations of the order parameter) and photo-induced superconductivity. These experiments demonstrate the interesting possibility of manipulating superconductivity in nonequilibrium settings. However, the properties of nonequilibrium superconductors are not fully understood, and further theoretical explorations are needed. [mehr]

MPSD Seminar

5731 1465378311

Coupled Cluster Theory for Strong Correlations

Coupled cluster theory is the dominant method in wave function-based calculations in systems of small to moderate size. It provides exceptionally accurate predictions for a wide array of energetics and properties. Moreover, it is size extensive, meaning that it can fruitfully be applied to condensed systems, provided only that one has computational resources sufficient for the task. Unfortunately, coupled cluster theory often breaks down in the presence of strong correlations, such as those responsible for superconductivity or various magnetically-ordered states. [mehr]

CFEL Theory Seminar

5633 1464259543

Water splitting on hematite (Fe₂O₃) surfaces: insights from density-functional theory

The development of efficient ways to exploit the energy from the sun is an issue of major importance. Among possible solutions, the employment of solar energy to promote chemical reactions has the advantage of addressing the problems of harvesting, converting and storing energy at the same time. In this context, water splitting plays a central role both for direct hydrogen production and for the production of hydrocarbons. Therefore, great attention has been recently devoted to hydrogen production by means of photoelectrochemical (PEC) cells, via water splitting to molecular hydrogen and oxygen. The main challenge is to develop anode materials for these cells that can split water efficiently. [mehr]

CFEL Molecular Physics Seminar

5549 1464260111

The Art of Laser Ablation for Microwave Spectroscopy

Laser ablation has proved to be an extremely versatile sampling technique for non‐volatile samples in a range of gas phase experiments. [mehr]

MPSD Seminar

4315 1453997465

Ultrafast Electron Dynamics and Circular Dichroism in Dependence of the Stoichiometry of Topological Insulators

[mehr]

MPSD Seminar

4313 1453997587

Manipulating electronic structure and transport in correlated oxide heterostructures

[mehr]

 
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