Open Positions

Demsar 1: Ultrafast manipulation of magnetic order with strain pulses

A PhD position is available in the field of ultrafast phenomena in magnetic systems. In particular, the focus of this project is to investigate an interplay between structure and magnetic order and to study magnetic switching triggered by picosecond strain pulses. Here (sub)picosecond strain pulses will be generated using femtosecond laser pulses. By studying the resulting changes in magnetization by means of magneto-optical Kerr effect (MOKE) we will be able to track the response of magnetization on structural distortion in real time with (sub)picosecond time resolution. Furthermore, the interplay between structural distortions and magnetism in magnetic shape memory alloys will be investigated. These studies are aimed to study the fundamental speed limits of potential spintronics devices, the nature of the coupling between the spin and lattice degrees of freedom, and their potential applications.
Our lab hosts several femtosecond time-resolved spectroscopic methods, ranging from time-domain THz methods, broadband white-light spectroscopy, time-resolved MOKE, to ultrafast transmission electron diffraction. In addition, advanced sample fabrication and characterization techniques are available at the Institute.
Potential candidate should hold a MSc or an equivalent degree in Physics or Materials Science. Preference will be given to candidates with experience in ultrafast laser technology/spectroscopy, magnetic materials or spintronics.

For further information and/or applications please contact, preferably via e-mail:
Prof. Dr. Jure Demsar (JGU Mainz)
http://www.demsar-lab.physik.uni-mainz.de/


Everschor-Sitte 1: PhD Position in Spintronics, JGU Mainz (Germany)

We are pleased to announce the opening of a PhD position in theoretical condensed matter in the Institute of Physics at the Johannes Gutenberg-Universität Mainz to work with Karin Everschor-Sitte and Jairo Sinova on skyrmion physics in topological materials with a focus on spintronics.
The institute and the Spin Phenomena Interdisciplinary Center (SPICE) provides a stimulating environment due to an active workshop program and a broad range of research activities.

A background in theoretical techniques in condensed matter physics is required. Candidates interested and/or experienced in skyrmion physics, magnetization dynamics, and micromagnetic modelling are highly suited for this opportunity. Programming experience, preferably in Python, are desired.
Further information can be found on the website. The prospective group member must hold a M.Sc. or equivalent diploma.

Johannes Gutenberg-Universität Mainz is an equal opportunity, affirmative actions employer in compliance with German disability laws. Women and persons with disabilities are encouraged to apply.

Review of applications begins immediately and will continue until the position is filled. Interested applicants should send a curriculum vitae, a list of publications, and at least two letters of recommendation to . When sending applications please use the subject line “Skyrmion PhD position application”.

Dr. Karin Everschor-Sitte
Head of the Emmy Noether Research Group “TWIST – Topological Whirls In SpinTronics”
Johannes Gutenberg-Universität Mainz
FB 08 – Institut für Physik
Staudingerweg 7
55128 Mainz
Germany
E-mail:
Phone (office): +49 6131 39 23645
http://www.twist.uni-mainz.de/
http://www.sinova-group.physik.uni-mainz.de/
http://www.spice.uni-mainz.de/


Heinze 1: Chromophores for dye-sensitized solar cells and light-emitting electrochemical cells

Transition metal complexes with strong metal-to-ligand charge transfer bands can be successfully employed in the area of photochemical energy generation, photocatalysis and in light-emitting devices as phosphorescent materials. Especially complexes with tridentate ligands are highly suitable due to their chemical and photochemical stability. The aim of replacing expensive noble metals by earth abundant metals is quite challenging as the photophysics and chemical stability requirements are typically hardly fulfilled with 3d metal ions. The PhD student will explore the feasibility of using 3d metal ions with thoroughly designed ligands in these applications.

Prof. K. Heinze (JGU Mainz)
https://www.blogs.uni-mainz.de/fb09ak-heinze/


Heinze 2: Electron transfer along molecular wires

Towards an increasingly smaller scale of electronic devices molecular entities capable of transferring charges over large distances are required. Furthermore, these molecular systems are required to be assembled/oriented in a defined fashion. The PhD student will explore the synthesis of oligomeric ferrocene peptides as well as oligomeric porphyrin amides and their application as molecular wires on surfaces.

Prof. K. Heinze (JGU Mainz)
https://www.blogs.uni-mainz.de/fb09ak-heinze/


Hillebrands 1: Magnon caloritronics

The realization of insulator-based spintronics, operating with pure spin currents decoupled from electron motion, potentially provides the basis for a fundamentally new signal-processing paradigm. In magnetic insulators spin angular momentum and energy can be transferred by magnons, the quanta of spin waves. The purpose of our studies is to find new ways to utilize coherent magnon currents for information processing in modern microwave devices by understanding the mechanisms responsible for the interplay between planar spin and heat transport in thin films and waveguides. Also our studies will focus on the mechanisms of generation, detection, and amplification of spin waves or magnons by electron currents using both the direct and inverse spin Hall effects. Time-, space- and wavevector-resolved Brillouin light scattering spectroscopy as well as microwave techniques and infrared thermography will be used in our study. The work will establish milestones in the development of magnon based spintronics and its integration with conventional electronics.

Applicants should have a Master degree (or equivalent) in Physics or Engineering, or a related discipline. They should be interested in experimental research and a background in the fields of basic magnetism, wave physics, and thermodynamics is appreciated.

Prof. Dr. Burkard Hillebrands (TU KL), Dr. Vitaliy Vasyuchka (TU KL)
http://www.physik.uni-kl.de/hillebrands/home/


Jakob 1: Thermoelectrics

Research on thermoelectric materials has strongly increased in recent years due to their high application potential. With steadily rising energy costs and carbon dioxide concentration in the atmosphere, the possibility to generate electricity from otherwise unused heat by using thermoelectric materials is becoming ever more attractive.

In the proposed project thin film superlattices of nanostructured Heusler compounds with C1b structure will be utilized as thermoelectric model systems. The theoretical study of the materials will go hand in hand with the experimental realization of nanostructured epitaxial C1b superlattices and measurement of their thermal and electrical parameters.

TiNiSn and Zr0.5Hf0.5NiSn will be used as a starting combination of materials. Both materials possess a high thermoelectric power factor. However, due to the different atomic masses one expects pronounced differences of the phonon related properties. By magnetron sputtering deposition epitaxial superlattices will be produced of this material combination. The inner interfaces of the superlattices will enhance the phonon scattering. As substrates we intend to use also dissolvable materials, which will allow us to measure free standing films.  A strong interaction between the project partners (Zuerich Switzerland and Mainz) will guarantee the information feedback between theoretical modelling, nanostructured film growth and measurement in order to optimize and understand the model system.  

Prof. G. Jakob (JGU Mainz)
http://www.klaeui-lab.physik.uni-mainz.de/290.php


Jakob/Kläui 1: Spincaloritronics

The interplay between spin and heat transport has recently stirred much attention. It was shown that temperature gradients associated with heat currents can generate spin currents in magnetic nanostructures. Furthermore, these thermal spin currents can also be used to manipulate magnetization.

We want to show how the electron spin can be used to modify the heat conductivity in spin caloritronic devices and materials. In the field of spintronics most materials are used as thin film systems or as complex heterostructures. While the electrical transport is well investigated in such systems, the corresponding transport of energy in form of heat is scarcely considered up to now. Using a 3ω method one can get access to the heat conductivity in thin film geometry. We want to measure and manipulate the heat conductivity of thin film systems. A second part of the project will be dedicated to the Spin Seebeck effect, where the spin is manipulated by the heat current.

During the PhD programme, the student will have the opportunity to collaborate with partners from other universities within the Priority Program.

Prof. G. Jakob and Prof. Dr. M. Kläui (JGU Mainz)
http://www.klaeui-lab.physik.uni-mainz.de/


Jourdan 1: Strain induced magnetic anisotropy

The relation between structural and magnetic, i.e. spin-related, properties is one of the most fundamental aspects of solid state physics. The magnetically ordered state of solids can be influenced by various externally controllable parameters. For spintronics applications in most cases Oersted fields, spin-transfer torques (STT) and spin-orbit torques (SOT) are employed. Alternatively, structural distortions modify magnetic properties. Such modifications provide means for voltage controlled switching of thin magnetic films on piezoelectric substrates, presenting new pathways for future spintronics with low energy consumption. Combined with new compounds, like the antiferromagnet Mn2Au with strong spin-orbit coupling and broken inversion symmetry on the spin sublattices, novel spintronics devices may emerge.

PD Dr. Martin Jourdan (JGU Mainz)
http://www.klaeui-lab.physik.uni-mainz.de/


Kläui 1: Graphene Spintronics

We are working on novel effects that occur due to the interaction of spin currents andmagnetization, spin dynamics and quantum effects in novel materials such as graphene nanoribbons and turbostratic graphene. These materials are very topical and highly interesting from scientific point of view (a large number of high impact publications in Nature, Science and Physical Review Letters have been published). Furthermore they are also promising for applications in data storage, sensors, logic and high frequency microwaves sources.
 
Prof. Mathias Kläui, JGU Dpt. of Physics
http://www.klaeui-lab.physik.uni-mainz.de/


Kläui 2: Graphene and Organic Spintronics

In the Department of Physics, University of Mainz, a PhD position is available in the field of spintronics in graphene and other carbon-based nanostructures. In particular we are working on novel effects that occur due to the interaction of spin currents and magnetization, spin dynamics and quantum effects in novel materials such as graphene nanoribbons and turbostratic graphene. The work is carried out in an interdisciplinary environment at the forefront of chemistry, physics and polymer science. These materials are very topical and highly interesting from scientific point of view as they exhibit high mobilities, long spin diffusion lengths and long spin lifetimes, which are the prerequisites for spin-based quantum computing. Furthermore they are also promising for applications in data storage, sensors, logic and high frequency microwaves sources.

The lab boasts advanced fabrication techniques (full clean room with lithography and pattern transfer techniques), a range of materials deposition tools (molecular beam epitaxy, sputtering, pulsed laser deposition, etc.) and a number of sophisticated characterization techniques. Low temperature magneto-transport measurements (10mK to room temperatures with fields up to 15T) will be carried out to detect spin injection, spin dynamics and quantum transport effects. A novel scanning electron microscope with polarization analysis was recently acquired within a Starting Independent Researcher Grant of the European Research Council that allows for high resolution magnetic imaging.

Possible applicants need to hold a Masters or equivalent degree in Physics or Materials Science. Experience in magnetic materials or spintronics is an advantage. For enquiries and applications including a full CV contact Prof. Dr. M. Kläui (Email: klaeui@uni-mainz.de, Tel. +49-6131-3924345) and see http://www.klaeui-lab.physik.uni-mainz.de/

Prof. Dr. M. Kläui (JGU Mainz)


Orus 1: Tensor Network algorithms with non-abelian symmetries: frustrated quantum antiferromagnets and beyond
A number of recent results in the field of quantum information science have lead to new and fresh ideas to attack old, long-standing problems in condensed matter physics. The study of quantum correlations (or
entanglement) has motivated the development of a host of new methods to understand quantum many-body systems based on entanglement and tensor networks. The research of the PhD student will concern the development and application of these new methods. In particular, the student will focus on devising and programming a library to manipulate tensors with non-abelian symmetries such as SU(2), which will be later used to simulate important physical models, focusing on frustrated quantum antiferromagnets and the search of novel states of quantum matter.

Students with a good background on quantum mechanics, statistical mechanics, computer programming and linear algebra would be desirable.

 

J-Prof. Dr. Roman Orus (JGU Mainz)
www.romanorus.com


Ott 1: Dissipative engineering of many-body quantum states

Dissipative processes can be a powerful resource for the controlled formation of complex many-body quantum states. Despite the presence of losses, dephasing or decoherence, a system can evolve into a state which is stable against these mechanisms. In turn, the precise engineering of dissipative processes allows for the formation of a specific state. Such states are then robust against perturbations. In our experimental group, we study ultracold quantum gases which are subjected to local losses and dephasing. To this end, we employ high resolution manipulation techniques which are based on laser and electron beams. The PhD student will investigate different scenarios to engineer stable many-body states in optical lattices or bulk systems and will look for dissipation induced quantum phase transitions.

Prof. Dr. Herwig Ott (TU KL)
http://www.physik.uni-kl.de/en/ott/home/


Palberg 1: Electrokinetic behaviour of charged sphere mixtures

Binary mixtures of charged spheres in aqueous suspension are an important model system to study soft matter transport phenomena in external electric fields. While much is already well understood about their behaviour at moderate to high concentrations, their behaviour in the dilute regime shows qualitative and quantitative deviations from theoretical predictions. Of particular interest are questions like the dependence of electrophoretic motion on total concentration and composition, on the physico-chemical processes conecting charging processes to mobilities, and on the surface potential of spheres in environments of like and unlike spheres. The PhD student will employ state of the art light scattering techniques (Integral Super heterodyne Small Angle Reference Beam Doppler Velocimetry) and high resolution microscopy with image processing. The electrokinetic characterization will be followed by application of the results to binary charged sphere phase behaviour, possible phase separation under shear and modular micro-swimming

Prof. T. Palberg (JGU Mainz)
http://kolloid.physik.uni-mainz.de/


Palberg 2: Liquid-solid interfaces under stress

Granular matter like sand is known to form ripples and/ or dunes if overflown by a fluid or air. If the granule size is reduced to colloidal scales (100nm-1µm) systems become buoyant andsolid-liquid phase separation under flow can be controlled applying e.g. electric fields normal to the flow direction. Again ripples are formed. If in addition the particle size is made monodisperse, the solid may take a crystalline order and one obtaines crystallized dunes wandering with the applied flow in the supernatant fluid phase. Proof of principle has already been given. Starting from a well performing flat cell of variable height The PhD will concentrate on realiziation of a new Hele-Shaw flow cell allowing precise control of experimental conditions and reproducible, systematic data recording. In addition to this practical task, numerical developments are necessary to adapt existing software for image analysis to the needs of determining in solid flow fields, monitoring dislcation motion, characterizing ripple size and speed etc.

Prof. T. Palberg (JGU Mainz)
http://kolloid.physik.uni-mainz.de/


Palberg 3: Crystallization from a Wigner Glass

Colloids are formidable experimental models for an analog simulation of statistical mechanics problems. The hard spher glass transition and its connection with crystallization has been studied extensively and with quite some success. The present PhD will pursuit the topic of crystallization from a glasy state in another model: highly charged spheres suspended in deionized water. If the spheres are sufficiently monodisperse, one observes long lived glassy states just above the freezing concentration. The full range of state of the art light scattering techniques will be employed to first comprehensively characterize the systems and then study both their vitrification and crystallization dynamics. Torsional Resonance spectroscopy provides insights about the development of elastic properties, Photon-Correlation Spectroscopy allows to study self- and collective diffusion processes, Two-Color-DLS features investigations of highly concentrated samples.

Prof. T. Palberg (JGU Mainz)
http://kolloid.physik.uni-mainz.de/


Rentschler 1: Phosphonate Ligands in Extended Organic/Inorganic Hybrids

Inorganic oxides display a variety of useful properties e.g. as molecular sieves, catalysts and magnetic storage. Modifying inorganic materials by incorporating organic ligands is one to build novel materials retaining some properties of the parent structures. An important field of interest is the investigation of the magnetic behaviour of hybrid inorganic-organic framework compounds. Creating low-dimensional magnetic materials in a rational way by having control over the kind of connectivity offers is still a challenging subject in the field of molecular magnetism. The PhD student will focus on new transition metal phosphonates for which control over the dimensionality of the resulting transition metal(II) phosphonate compound is gained. The structural characterization will be followed by detailed investigations of the electronic and magnetic properties.

Prof. E. Rentschler (JGU Mainz)
www.ak-rentschler.chemie.uni-mainz.de  


Rentschler 2: Linking high spin transition metal cages using polyfunctional ligands

Molecular clusters of 3d transition metals continue to be a main research area due to their fascinating physical properties and their complex structures. In particular, they often show high-spin ground states and easy-axis-type magnetic anisotropy, giving a significant energy barrier to reversal of the magnetization. Thus, at sufficiently low temperatures they behave as nanoscale single domain magnets (SMMs). Magnetic molecules have been proposed as a novel route to a spin-based implementation of quantum-information processing. Within this field, the assembly of pre-formed polymetallic clusters by covalent bonds in a step-by-step strategy has become a quite desirable goal for chemists. However, very few examples has been reported of discrete covalently attached 3d transition metal clusters and even in a less number of examples a rational strategy has been employed. The PhD student will focus on linking basic carboxylate cores of transition metals with appropriate bridging units through covalent bonds. The structural characterization of all compounds will be followed by detailed investigations of the electronic and magnetic properties.

Prof. E. Rentschler (JGU Mainz)
www.ak-rentschler.chemie.uni-mainz.de 


Rizzi 1: Frustration, topology and other exotic many-body effects

The research activity will be focusing on many-body effects generated by the interplay of geometry, interactions and gauge fields. Examples range from localization effects and uncommon superfluid pairings to topological states of matter and their possible use for quantum technologies. Particular attention will be devoted, according to the inclination of the candidate, to one of the following directions:
a) development of quantum simulation schemes with cold atoms or trapped ions;
b) theoretical analysis to identify some minimal requirements to generate interesting states;
c) numerical investigations to determine phase diagrams and to support the other two research lines.
Point a) will profit from the vicinity of experimental groups like the ones of Prof. Schmidt-Kaler and Prof. Windpassinger, and point c) also from the neighboring group of Jun.-Prof. Orus.

Jun.-Prof. Dr. Matteo Rizzi (JGU Mainz)
http://www.rizzi-matteo.com/


Speck 1: Interplay of structure and dynamics in dense amorphous materials

Dense amorphous materials such as glasses and gels play an important role for both our fundamental understanding and in technical applications. For example, the prediction (and avoidance) of devitrification represents a major challenge. What is puzzling is that these systems respond to a change of temperature/density with seemingly small changes in structure but enormous changes in the dynamical behavior. In this project, we study dynamic processes and pathways in several, initially disordered model systems by means of molecular dynamics simulations and analytic theory. Students interested in the project should have a Masters degree in Physics (or a related discipline), a working knowledge of statistical mechanics, and be interested in advanced statistical physics and stochastic processes.

Prof. Dr. T. Speck (JGU Mainz)
http://www.komet331.physik.uni-mainz.de


Sulpizi 1: Liquid/Solid interfaces: Structure and spectroscopy from first principles simulations

Liquid-solid interfaces play an important role in a number of phenomena encountered in biological, chemical and physical processes. Surface-induced changes of material properties are not only important for the solid support but also for the liquid itself. In particular it has been shown that water at the interface is substantially different from bulk water, even in proximity of apparently inert surface, such as a simple metal.The complex chemistry at solid-liquid interfaces is fundamental to heterogeneous catalysis and electrochemistry and has become especially topical in connection with the search for new materials for energy production. A quite remarkable example is the development of cheap yet efficient solar cells, whose basic components are dyes molecules grafted to the surface of an oxide material and in contact with an electrolytic solution. This PhD project propose the use of first principle molecular dynamics simulation to investigate the structural and spectroscopic properties of solid/liquid interface. First principle simulations permits to give a realistic description of interfaces where polarization effects (including electronic polarization) and finite temperature dynamics are naturally included. Collaboration with experimental groups working on vibrational spectroscopy of solid/liquid interface will permit to validate the computational approach and to verify theoretical predictions.

Jun.-Prof. Dr. M. Sulpizi (JGU Mainz)
http://www.komet331.physik.uni-mainz.de/index.php


Sulpizi 2: First principles computational modelling of bio-hybrid interfaces for energy conversion

This PhD project focuses on the computational investigation of the microscopic mechanisms underlying energy conversion processes in bio-hybrid systems. The final aim is to predict the impact of the properties of the system on the reaction rates, which may guide the design of more efficient catalysts.Expanding and diversifying the sources of energy available to mankind arguably represents one of the most fundamental challenge now faced by society. Harvesting energy directly from the Sun and refining and concentrating the energy content of low-grade biomass are two of the most promising options for our future. The success of life and its ability to exploit nearly all forms of energy, including the lowest grade ones, is the motivation of bio-hybrid approaches to recover, concentrate, transform and store energy. Enzymes and bio-inspired synthetic catalysts can be merged with materials to develop cost-effective, renewable alternatives to the expensive noble-metal catalysts (e.g., platinum) that are currently used in artificial devices. However scaling up the processes for a commercial exploitation requires the engineering of interfaces which are both catalytically efficient and stable. A microscopic view of the chemical reactions taking place in those systems can be obtained by computer simulations, which complement the experimental observation and help to interpret it. This work aims to (i) identify the detailed steps in the energy staircase followed by the electrons from the catalytic centre to the electrode/ conducting material; (ii) quantify how fast they can move across the molecular bridges and conducting supports. The novelty stems from the application of my original modelling approach, based on first principles description of the reactive centres AND their heterougeneous environment, to fundamental electrochemical processes. In particular we will consider bio-hybrids where a nature-inspired catalyst is combined with conducting materials based on carbon.

Jun.-Prof. Dr. M Sulpizi (JGU Mainz) 
http://www.komet331.physik.uni-mainz.de/index.php


Zabel/Elmers 1: Spin dynamics of spintronic materials in the frequency and time domain

X-ray magnetic circular dichroism (XMCD) and resonant x-ray magnetic scattering (XRMS) are powerful methods for the element specific analysis of magnetic materials on the nanoscale. They are particularly important for the understanding of spintronic materials and their interfaces. In recent years these methods have been carried forward into the time and frequency domain by utilizing the time structure of modern synchrotron radiation sources of the third (undulator insertion devices) and fourth generation (x-ray free-electron laser). With laser pump – x-ray probe techniques the free precessional spin dynamics can be studied on the picosecond time scale up to the ultrafast demagnetization of ferro- and antiferromagnets on the femtosecond timescale. Vice versa, using time resolved and element specific ferromagnetic resonance techniques (XFMR), additional information can be gained on the phase relationship between microwave excitation and precessing magnetization in heterostructures such as spin valves. In the proposed PhD work the candidate will study with state-of-the-art experimental methods based at x-ray synchrotron radiation sources the dynamics of spintronic materials in the frequency and time domain.

Applicants should have a Master degree (or equivalent) in Physics or Engineering, or a related discipline. They should be interested in experimental condensed matter research and a background in one of the following fields: femtosecond lasers/photoemission/x-ray or neutron scattering, pulse-probe techniques.

Prof. Dr. Hartmut Zabel (JGU Mainz) http://www.mainz.uni-mainz.de/1655.php
Prof. Dr. Elmers (JGU Mainz) http://www.komet335.physik.uni-mainz.de/index_ENG.php