Open positions of CRC 1242

What we offer:

You will be a key player in one of the scientific projects of the Collaborative Research Centre (CRC) 1242 and will do research in a highly cooperative and excellent scientific environment. We provide you with research experience in an international context and ensure that you develop scientific independence and the skills to work successfully in a team. In addition, the Internal Research Training Group (IRTG) will help you to develop the skills necessary for a future career in academics or industry.

Since several types of activities organised by the graduates among themselves act as catalysts for team building, participation in these also will allow you to develop and test your self-reliance. Moreover, the IRTG supports a one-month exchange visit to a partner laboratory abroad during the course of your PhD work

What we expect:

Aside from excellent performance in your studies, we anticipate that you have a great enthusiasm for science and a keen interest in attaining research goals. Furthermore, we expect your participation in the joint organisation of the IRTG and its activities, such as workshops, training courses and presentations

How to apply:

Send your application form and a CV to Prof. Eckart Hasselbrink. Qualified Master of Science or comparable degree (i.e. 4 years of studies) required.

 

Salaries are according to the TV-L scale up to 75% of level E13.

Description

The PhD student will be involved in setting up a new scanning tunnelling microscopy (STM) experiment that combines STM with pump-probe schemes using THz radiation and electronic voltage pulses.

In this project, the PhD student will familiarize with time resolved pump-probe STM and acquire knowledge about charge carrier dynamics on the atomic scale to compete with the leading experts in the field of the charge transport dynamics at the nanoscale.

Desired skills and experience

Applicants should be interested in challenging experimental setups and experienced with STM instrumentation and design. In the initial stage, the THz part of the experiment shall be performed under ambient conditions. During further progress the experiments shall be extended to ultra-high vacuum (UHV) so that experience with vacuum equipment is beneficial.

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B1 (Ligges, Bovensiepen): Local and Non-Local Relaxation Dynamics of Hot Carriers

Description

An experimental analysis of the spatio-temporal correlation of hot electrons propagating in heterostructures using time-resolved photoelectron spectroscopy shall be carried out by this project’s student. The activity comprises preparation and the conduction of first experiments on Fe/Au heterostructures, in which optical excitations in a Fe layer generated by femtosecond laser pulses are analyzed by pump-probe techniques at a different position in space on the Au surface similar to a time-of-flight experiment inside a material.

 

The PhD student will acquire expert knowledge in a variety of fields, including ultrafast laser systems and physics, ultrahigh vacuum technology, surface preparation and characterization methods and photoelectron spectroscopy. He or she will be incorporated into a well established research group that combines expertise in these and other fields in the context of ultrafast science.

Desired skills and experience

You should have a degree in physics, laser science or related field and should be interested in challenging, state-of-the-art experimental setups. Knowledge and/or experience in one or more of the above mentioned areas is desired, but by no means necessary.

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Description

The PhD student shall study the time evolution after a quench/excitation for experimentally relevant model Hamiltonians (e.g., Fermi-Hubbard model), especially in the regime of strong correlations. The goal is the theoretical understanding of the dependence of this temporal evolution on the intrinsic dynamics of the system, the initial conditions (e.g. temperature), and the specific mechanism of excitation or quenching.

To this end, mainly analytical methods shall be developed and applied (possibly supplemented by numerical simulations, when appropriate).

Thereby, the PhD student will develop expertise with advanced analytical approaches to many-body quantum dynamics.

Desired skills and experience

Master in Theoretical Physics, preferably with emphasis on analytical methods. Experience with many-body quantum dynamics (e.g., in solid state physics or optical lattices) are advantageous.

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Description

This challenging experimental PhD project is devoted to the ultra-fast non-equilibrium structural dynamics of the phonon system of surfaces and thin films. Upon excitation of the electrons with fs-laser pulses the lattice system reacts delayed due to electron-phonon coupling on a time scale of a few ps. The dynamics of such processes and the underlying fundamental processes are so far “terra incognita” and will be studied by ultrafast time resolved electron diffraction in a pump-probe setup.

As the project relies on several modern experimental methods, the PhD student will gain a profound knowledge in a variety of techniques. Ultrafast reflection high energy electron diffraction (RHEED) with an unmatched temporal resolution of 330 fs together with femtosecond laser pulses form the experimental basis for the project. Samples are in-situ prepared using molecular beam epitaxy. Scientifically, the PhD student will study electron phonon coupling, mode conversion in adsorbate systems, nanoscale heat transport in thin films, and ultrafast phenomena at surfaces of solid state matter.

Desired skills and experience

 

A degree in Physics (experimental physics) is required, preferably with a background in surface science or ultrafast phenomena. A keen interest in dynamics of ultrafast processes at surfaces and surface electron diffraction is needed, along with a talent to manage and maintain extensive experimental setups. 
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Description

This challenging PhD project is devoted to nonlinear electron emission triggered by surface plasmon polaritons. Surface plasmon polaritons are longitudinal electron density waves that can be excited by a femtosecond laser pulse and that propagate along the surface of a noble metal. It is the aim to understand the electron emission in the presence of extremely intense plasmonic excitations, and to manipulate the electron emission pathways by forming plasmonic foci both in the presence and absence of nanoparticles. The distinction between light- and plasmon-induced emission processes in time and space is accomplished in a femtosecond time-resolved photoemission microscopy experiment.

As the project relies on several modern experimental methods, the PhD student will gain a profound knowledge in a variety of techniques. Low Energy Electron Microscopy and Photoemission Electron Microscopy in conjunction with femtosecond laser pulses form the experimental basis for the project. Samples are prepared using molecular beam epitaxy and focused ion beam milling. In collaboration with project A1, the PhD student will integrate nanoparticles into the plasmonic focusing structures. Scientifically, the PhD student will learn about surface plasmon polaritons, nonlinear electron emission, ponderomotive acceleration of electrons in confined structures, and plasmon-nanoparticle interaction.

Desired skills and experience

A degree in Physics (experimental physics) is required, preferably with a background in surface science, plasmonics, or ultrafast phenomena. A keen interest in surface plasmon related phenomena and surface electron microscopy is needed, along with a talent to manage and maintain extensive experimental setups.

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Description (position 1)

It is the task of this PhD project to perform simulations of electronic relaxation in both weakly and strongly correlated electronic materials using methods from non-equilibrium statistical physics. For this purpose, a computer code solving quantum-statistical rate equations should be developed and tested. Moreover, suitable model Hamiltonians governing electron dynamics will be developed, using external input from DFT calculations of specific systems and/or from quantum-mechanical many-body  approaches. The goal is to understand equilibration of the electronic system after an excitation by a stimulus on the femtosecond scale, and to identify regimes where different relaxation mechanisms (electron-electron interaction, electron-phonon interaction, etc.) are dominating.

The PhD student will gain a profound understanding of modern methods in non-equilibrium statistical physics. Numerical techniques and code development will be an important part of the work. This includes access to supercomputers with thousands of CPU cores.

Desired skills and experience

Studies in Physics with a focus on condensed-matter physics or many-particle physics. Acquaintance with computers running under Unix/Linux, good programming skills in Fortran or C. Knowledge in numerical techniques for rate equations / transport equations is an advantage.

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Description (position 2)

The goal of this PhD project is to develop a theoretical approach for treating the non-equilibrium quantum dynamics of many particles on a lattice, where these particles interact with each other and with an external environment/bath. This goal shall be achieved by intertwining different theoretical approaches, such as strong-coupling perturbation theory, to hierarchy of correlations, Lindblad master equations, and diagrammatic real-time methods.

Thereby, the PhD student will get familiar with advanced analytical approaches to many-body quantum dynamics.

Desired skills and experience

Master in Theoretical Physics, preferably with emphasis on analytical methods. Experience with many-body quantum dynamics (e.g., in solid state physics or optical lattices) are advantageous.

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Description

This challenging experimental PhD project is devoted to the ultra-fast non-equilibrium structural dynamics of photo induced phase transitions at surfaces. The initial dynamics of the atoms, the evolution of so-called hidden states and the recovery to the ground state shall be studied by means of ultrafast time resolved electron diffraction in a pump-probe setup. The phd student will contribute to the design and setup of a new ultra-compact diffraction chamber aiming for a temporal resolution of less than 200 fs (FWHM).

As the project relies on unique experimental methods, the PhD student will gain a profound knowledge in a variety of modern techniques. Ultrafast reflection high energy electron diffraction (RHEED) with an attempted temporal resolution of less than 200 fs together with femtosecond laser pulses form the experimental basis for the project. Samples are in-situ prepared using molecular beam deposition. Scientifically, the PhD student will become an expert in the fundamental quantum processes which drive a system into a non-equilibrium state when undergoing a phase transition.

 

 

Desired skills and experience

 A degree in Physics (experimental physics) is required, preferably with a background in surface science or ultrafast phenomena. A keen interest in dynamics of ultrafast processes at surfaces and surface electron diffraction is needed, along with a talent to manage and maintain extensive experimental setups.

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Description

This PhD student will work with a brand-new, state-of-the-art lasersystem allowing to time-resolve the energy flow between molecular vibrations in an adsorbate layer in unprecedented detail. She/He will conduct with this instrument studies on organic monolayers prepared in our laboratory. 

He/she will ain hands-on-experience with a very advanced lasersystem and its application in molecular sciences. She/he will need to learn modern techniques of non-linear IR laser spectroscopy and the fundamentals of molecular vibrations. Data analysis requires the modelling of complex spectra. The experiment mandates the managing of a most complex experiment which nevertheless fits on a table top.

Desired skills and experience

The candidate should have a keen interest in experimental studies of molecular processes. Expertise in laser spectroscopy, non-linear optics and/or preparation of organic monolayers are of advantage. The project is suitable for a person with a background either in physics or chemistry.

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Description

This project will study particle induced non-equilibrium in solids in a novel, challenging way. The student will be involved in the design, building and optimizing of a novel ion source with (sub)-picosecond pulse duration as well as suitable diagnostic concepts.

She/he will have the opportunity to deepen her/his experimental skills, to gain significant expertise in the field of solid state, ion and laser physics.

Tasks:

  • Design and construction of a high repetition pulsed supersonic nozzle expansion beam
  • Set-up of optical components for short-pulse photo-ionisation and pump-probe experiments
  • Quantitative characterization of photo-ionized particles by means of mass spectroscopy
  • Design and construction of pulse diagnostics: adaption of a streak camera, layout and construction of the UHV ionization chamber, design and implementation of ion pulse duration measurement

Desired skills and experience

As this project requires the combination of several complex techniques (see tasks above), we are looking for a candidate with a strong background in experimental physics, and preferably with experience in ultra-high-vacuum, pulsed atomic and molecular beams, surface science, or laser physics. The successful candidate must be able to collaborate in a team, to take responsibility for assigned tasks, and to deal with the requirements and difficulties of a challenging long-term project.

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