Research Phase and Master's Thesis in the Physics programs

The recent detection of gravitational waves (GW) with the advanced LIGO/Virgo instruments in conjunction with a short gamma-ray burst (GRB) has surprised gamma-ray astronomers because of the substantially different properties of the GRB  signal as compared to canonical GRBs. This motivates an "open-mind" search for untriggered transient events in the data stream of the gamma-ray burst monitor (GBM) on the Fermi satellite. With two previous Bachelor theses we have developed a physical background model, paving the way for automated searches, and subsequent source and background fitting.
 
This thesis shall be devoted to establishing a Python program for identifying long-term (> few minutes up to a year) transients in Fermi/GBM data, localizing them on the sky, and deriving basic properties (spectrum, light curve). One pot\ential application is to determine the spectral properties of the predicted seasonal variation of the background due to axions. The project includes elements from computational and observational high-energy astrophysics, and will allow for obtaining extensive knowledge on the broad class of high-energy transients. 
 
Some background in astrophysics is advantegeous, but affinity with Python programming is a must. 
 
Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847

Background:
Microbeam radiation therapy (MRT) is a novel, still preclinical approach for cancer treatment that uses micrometer sized x-ray treatment fields. One of the major obstacles for a clinical application of MRT is the availability of appropriate radiation sources. Currently only large synchrotrons provide the necessary dose rates and radiation quality required for clinical treatments. In our team, we developed a system that generates microbeams for preclinical studies with a conventional x-ray tube. In order to analyze the MRT dose distribution with focus on the effect of pulse and breathing motion, we are currently seeking a motivated and curious master student.

Tasks:
- Design and fabrication of a phantom to analyze effects of motion on the physical dose distribution of microbeams
- Phantom measurement of the motion effects at our preclinical x-ray source
- Possible: Simulation of the motion effects with Monte Carlo (TOPAS)
- Ex-/In-vivo experiments at our preclinical treatment machine with an interdisciplinary team of physicists and biologists
- Possible: Development of in-vivo gating (e.g. ECG or breathing gating) including programming a user interface for our preclinical treatment machine

Profile:
- Genuine interest in medical physics
- Advantage: programming skills (e.g. Matlab, Python, or C++)
- Advantage: wet lab experience

Contact: stefan.bartzsch@tum.de

The ability to robustly assemble and maintain complex intracellular structures is fundamental for cell function. The budding yeast septin ring, which sets the basis for bud formation and downstream assembly of the contractile actomyosin ring, is one of the best-studied biological self-assembly processes and serves as an important model system to understand cell polarization and non-linear feedback dynamics. However, what determines the the diameter of the emerging ring structure is so far unclear.

Recently, our lab was able to demonstrate that cell size sets the septin ring diameter in an actin-dependent manner. Aim of this thesis is to use a combination of molecular biology, genetic manipulations, live-cell imaging and image analysis to reveal the molecular processes that underlie the observed scaling of ring diameter with cell volume. Ultimately, theoretical modelling will be used to obtain a quantitative understanding.

This project will be carried out together with the Schmoller lab, Helmholtz Zentrum Neuherberg

Quantum technologies are on the verge of revolutionizing high-security communication owing to advanced protocols such as teleportation and remote-state preparation. Development of quantum local area networks (QLAN) is an important milestone in this field. Such a microwave QLAN can be realized as  superconducting transmission line cooled down to millikelvin temperatures.  In practice, this system requires careful characterization measurements with quantum signals propagating over the cryogenic link in order to determine the effective losses, noise level, and other imperfections.

In this work, the main goal is to investigate a new prototype of a quantum local area network (QLAN) established between two neighboring laboratories. This includes analysis of experimental results with theoretical and numerical methods. This project will provide you an excellent opportunity to gather expertise in a broad range of topics from quantum physics to microwave engineering and cryogenic techniques.

Topic:

III-V semiconductor nanowire lasers combine the superior optical properties of the established III-V materials with the possibility of a site-selective and monolithic integration on a common silicon-on-insulator platform. Their recent integration on silicon waveguides marked a crucial milestone towards their usage as coherent light sources for future silicon photonics applications. However, so far pumping of nanowire lasers is done opticallywhile electrical injection is crucial for a useful application as on-chip light source.

The goal of this M.Sc. project is the realization of standing nanowire lasers on a silicon platform and the characterization of their electrical and electro-optical properties. Hereby, you will be closely working together with a PhD student. Your work will be settled over the whole fabrication process line from the first design of sophisticated nanowire heterostructures over their fabrication further to their analysis. The design will be guided by simulations for optimized laser cavity properties as well as electronic simulations of the doped heterostructures. Nanowire lasers should then be realized on lithographically patterned substrates by various bottom-up/top-down nanofabrication processes, including state-of-the-art processing in cleanroom environment. From electrical and optical characterization of the wires you should derive correlations between heterostructure design, electronic properties, contact behavior and electroluminescence to drive the optical emission properties of the nanowires into the lasing regime.

Requirements

Experience in the area of clean room fabrication and nanoanalytics as well as experience in simulations would be beneficial. Furthermore, some data analysis skills would be good:

·     Python or MATLAB

·     Origin

·     MS Office

Nevertheless, the most important requirements are motivation and commitment.  

What you will gain and learn

·     Advanced clean room processes for state-of-the-art 3D structured nanowires

·     Nanoanalytics and imaging techniques (SEM, AFM)

·     Expertise in measurements of electrical and optical properties of nanowire heterostructures (Low-noise I-V characterization, Photo- & Electroluminescence spectroscopy)

In summary, you are going to develop hands-on experience on a substantial pool of nanofabrication and -analytics methodologies available at WSI/ZNN, while contributing to a technologically and scientifically extremely relevant topic in integrated photonics. Additionally, you will get the chance to work in a top semiconductor research institute with a productive working atmosphere and a great team spirit.

Application

If you are interested in this topic or if you have any questions please send a mail to tobias.schreitmueller@wsi.tum.de or gregor.koblmueller@wsi.tum.de. Please include your CV, transcript of records and your Bachelor’s Thesis.

Quantum experiments often require fast and versatile data processing which allows for a quantum feedback operation. This approach opens the road to many fascinating experiments such as quantum teleportation, entanglement purification,  quantum error correction, among others. Here, we would like to develop a specific measurement and feedback setup, based on a field programmable gate array (FPGA), for experiments with propagating quantum microwaves.

The main goal is to program and experimentally test a specific image for an FPGA  which would allow for acquisition of microwave signals and feedback generation over few hundred of nanoseconds. This timescale is the prerequisite for exploiting quantum correlations effects for quantum communication and cryptography protocols with propagating squeezed microwaves which are conducted in our lab. This project will offer a deep insight into the state‑of‑the‑art FPGA devices, microwave measurements, and cryogenic experiments with superconductors.

Josephson junctions (JJs) represent a fundamental building block of modern quantum circuits such as superconducting qubits or Josephson parametric amplifiers. The JJs are conventionally fabricated with Al while the surrounding quantum circuits are often made of Nb. Henceforth, there is a need of galvanic connection between them which includes removing Nb oxide via ion milling.  As a consequence, one needs to develop a careful milling and fabrication technique in order to preserve a low-loss microwave environment in the close vicinity of JJs. This task is of paramount importance for achieving high coherence times of the related quantum devices.

The goal of this Master project is to develop a fabrication technique for Al/Nb superconducting circuits which will include Ar/O2 milling. This also includes cryogenic microwave studies of fabricated superconducting circuits (such as Josephson parametric amplifiers and transmon qubits) and participation in experiments towards quantum information processing with superconducting devices.

A member of the k-(ET)₂X family to be studied in this Master thesis exhibits a novel state of matter, quantum spin liquid at ambient pressure. Under a moderate pressure of about 3 kbar the material becomes metallic and superconducting. The aim of the work is to trace the evolution of the conducting system, particularly, of correlation effects, in close proximity to the superconductor-insulator phase boundary. The intrinsic properties of charge carriers will be probed by high-field magnetoresistance effects with the focus on magnetic quantum oscillations. A part of the experiments will be done at the European Magnetic Field Laboratory in steady fields up to 30 T or in pulsed fields up to 80 T.

Physics: Correlated electron systems; magnetic quantum oscillations; unconventional superconductivity.

Techniques: Strong magnetic fields; high pressures; cryogenic (liquid ⁴He; ³He; dilution fridge) techniques; high-precision magnetoresistance measurements.

Contact person:  Mark Kartsovnik (mark.kartsovnik@wmi.badw.de) 

NEPOMUC provides the world’s most intense positron beam. The positron is a applied as unique probe for material defect studies, surface investigation and fundamental research in quantum physics.
For the experiments we typically use electrostatic acceleration to implant the positrons in the material, with the sample holder being charged to tens of kilovolts with respect to ground. In these conditions it is extremely difficult to subject the sample to electric currents or potentials during the measurement, which limits the use of e+ for novel in-operando studies relevant for the construction of batteries, solar panels and integrated electronics.
At NEPOMUC we are now developing an active sample holder which makes use of light to
both power its onboard instrumentation and to communicate with the control system.
As an applicant you will be tasked, with the support of the NEPOMUC team and the TUM
facilities, to build a prototype of such sample holder, test it and program its onboard MCU.
The work will involve the following tasks:

1. Progressive assembling of the sample holder, performing electrical tests to ensure functionality after every assembling step.
2. Programing the onboard MCU and running all of the subsystems of the sample holder in a test environment.
3. Designing a control protocol to be run over an IRDA optical bridge and implement it.
4. esting the autonomous functioning of the sample holder, with the system being powered through light and communicating through an optical bridge.
5. Testing the system in UHV conditions with a 30 kV bias applied.

As an applicant you will be given the opportunity to experience first hand the development of
highly specialized scientific equipment. We attach particular importance to the training aspect
during the internship; as such you are not required to be able to carry out the entire task by
yourself, but you will be helped and tutored by our team. This said a certain level of autonomy
is expected from you.

Hybrid materials combining nontrivial conducting and magnetic properties are of high current interest, especially in the context of potential spintronic applications. The organic charge transfer salts (BETS)₂FeX₄ with X = Cl, Br provide perfect natural structures of conducting and magnetic layers alternating on the single-molecule level. Our project is aimed at a quantitative study of the interaction between the two subsystems and of the role of the subtle structural modifications in this family. To this end, high-precision measurements of quantum oscillations in the electrical resistance and magnetization will be carried out on single crystals of these compounds under strong magnetic fields. The results will be analyzed in terms of electronic correlation and magnetic interaction effects.

Physics: Correlated electronic systems; magnetic ordering and superconductivity; magnetic quantum oscillations.

Techniques: Strong magnetic fields; magnetotransport; magnetic torque; cryogenic (liquid ⁴He and ³He) techniques.

Contact person:  Mark Kartsovnik (mark.kartsovnik@wmi.badw.de)

Nano-mechanical strings are archetypical harmonic oscillators and can be straightforwardly integrated with other nanoscale systems. For example, the field of nano-electromechanics studies the coupling of nano-strings to microwave circuits, which resulted in the creation of mechanical quantum states and concepts for microwave to optics conversion. Here, we plan to investigate an alternative hybrid system based on ferromagnetic nanostructures integrated with nano-strings or nano-mechanical platforms. These hybrid devices enable the design and the investigation of spin-phonon coupling down to the single excitation level and are expected to allow the investigation of the Einstein-de Haas on the nanoscale, where the angular momentum change arising from magnetization reversal is transferred into a mechanical vibration of the beam. In addition, these systems are key for the investigation of strong magnon-phonon coupling.

We are looking for a motivated master student for a nano-mechanical master thesis in the context of magnon-phonon interaction. The goal of your project is to investigate the static and dynamic interplay between the mechanical and magnetic properties of a nano-mechanical system sharing an interface with a magnetic layer. In your thesis project you will fabricate freely suspended nanostructures based on silicon nitride or silicon and deposit on them ferromagnetic multi layers using state-of-the-art nano-lithography and metal deposition techniques. Further, you will probe the mechanical response of the nano-structures using optical interferometry while exciting the magnetization dynamics of the magnetic system

The field of magnonics deals with exploiting the collective spin dynamics (spin waves) of magnetically ordered materials for computational purposes. Efficient and scalable schemes for controlling spin waves in thin film ferromagnets thus have large application relevance. The magnetic torques arising due to the spin-orbit interaction allow to control spin waves by electric currents and acoustic waves at GHz frequencies. We are particularly interested in a spatially-resolved study of the interaction of spin waves with acoustic and current-induced torques in nanopatterned devices with application potential for spintronics.

We are looking for a talented and highly motivated master student who is interested in joining our spin dynamics project. During your thesis, you will use state-of-the-art nanolithography and thin film deposition tools to fabricate hybrid devices that allow for the interaction of spin waves with electrical currents and acoustic waves. You will study spin waves in these devices using optical and microwave spectroscopy methods

Nano-mechanical beams are prototype harmonic oscillators, and can be straightforwardly integrated with other nanoscale systems. For example, coupling nano-beams to coplanar microwave cavities yields so-called hybrid electro-mechanical systems with intriguing properties, e.g., electro-mechanically induced transparency. In a similar fashion, ferromagnetic nanostructures can be integrated with nano-beams. This enables the design and the investigation of spin-phonon coupling down to the single excitation level, or nanoscale Einstein-de Haas experiments, in which the angular momentum change arising from magnetization reversal is transferred into a mechanical vibration of the beam. 

We are looking for a motivated master student for a magnetic nano-beam oriented master thesis. The goal of your project is to investigate the static and dynamic interplay between the mechanical properties of double layer nano-beams and its magnetic properties. In your thesis project you will fabricate freely suspended nanostructures based on silicon nitride and ferromagnetic multi layers using state-of-the-art nano-lithography and metal deposition techniques. Further, you will probe the mechanical response of the nano-structures using optical interferometry while exciting the magnetization dynamics of the magnetic system. 

Fault Injection through Laser irradiation is an established attack method in the context of hardwarebased IT-security. Faulty data can be exploited in various ways to break the security measures of an Integrated Circuit. These techniques are referred to as “Fault Attacks”. This project will address fault injection employing a state of the art ultra-short pulse laser system. With semiconductors being inherently sensitive to light, it is feasible to induce transient currents in a chip by irradiation. The goal is to optimize the light source taking into account nonlinear optics to utilize the dominant physics in the best possible way.

The thesis is performed in cooperation with the Fraunhofer Research Institution for Applied and Integrated Security (AISEC) and comprises the following tasks:

                Development of a laser workbench including IR generation.

                Systematic studies of the laser source (focusing, wavelength, pulse duration . . . ).

                Study of the fault injection on a model system.

Hybrid solar cells combine an inorganic and an organic component into a photovoltaic cell. They combine the advantages of inorganic materials (e.g. metal oxides: TiO2 or GeO) such as high charge carrier mobility and very high stability with those of organic materials (e.g. conducting polymers: PTB7) such as cost-effectiveness and flexibility. In comparison with standard silicon solar cells, the hybrid solar cells can be easily manufactured and can allow for alternative processing techniques as for example spray-coating and printing. In contrast to dye sensitized solar cells (DSSCs), hybrid solar cell devices contain no dye as active components and consequently problems such as photo-bleaching are mitigated. Moreover, all materials in the hybrid solar cells are solid and thus no sealing to protect against leakage of aggressive solvents such as in DSSCs is required. Regarding application, the hybrid solar cells are more environmentally friendly. Compared to organic solar cells, which are composed purely out of organic components, hybrid solar cells are expected to have higher lifetime stability. In particular, a degradation of the morphology, which is one pathway in organic solar cell degradation, cannot happen in the hybrid solar cells. The inorganic component acts as a corset to the morphology and prevents structural changes. Despite all these advantages of hybrid solar cells, so far most research on alternative solar cells beyond the silicon solar cells, has been focused on DSSCs and organic solar cells. hybrid solar cells have gained much less attention and therefore have a high undiscovered potential, which will be investigated in the present thesis based on novel pathways.

Introduction:

Computed tomography is a three-dimensional imaging method in which X-rays can be used to calculate slices of an object. Dual Energy CT uses the energy dependence of X-rays: The respective object is measured with different X-ray spectra, and the images obtained are subsequently processed and reconstructed. With the help of different algorithms, Dual Energy CT can extract much more information from the image than conventional imaging (monoenergetic images, electron density, material images, ...). Dual Energy CT devices are in use in human medicine since a few years; in this work the method is used on a small animal irradiation device for mice. Our dual energy method uses a calibration using calibration cylinders and two different X-ray spectra.

Tasks:

The master thesis focuses on the optimization of X-ray spectra and calibration and its effect on the measurement. When choosing the X-ray spectra, many combinations are possible by using different voltages and filters. The optimal combinations should be found by using different criteria and verified with a phantom. The calibration cylinders should be examined and improved with regard to their geometry and material. It should also be considered whether different calibration phantoms are advantageous for different measurement objects. Furthermore, it should be checked how stable the calibration is depending on the position in the device and the time. In all optimizations, the focus is on ensuring that the subsequent measurement of the object provides the most accurate possible result.

Requirements:

You are interested in medical physics, especially in X-ray diagnostics/radiotherapy?

You like to work experimentally and can imagine working in a clean room?

You have basic experience with Python and enjoy programming?

Contact:

Manuela Duda

manuela.duda@tum.de

Medical Radiation Physics / Prof. Wilkens

Klinikum rechts der Isar (MRI)

Pure spin currents are generated and/or detected via the spin Hall and inverse spin Hall effect in heavy metals. These two effects crucially depend on the magnitude of the spin-orbit interaction. The goal of this thesis is to investigate the spin Hall physics in oxide systems, where large spin orbit interaction is prevailing like in the transition metal oxides. In particular, the realization of epitaxial multilayers of a spin Hall active material and a magnetically ordered insulator are a major task of this research project. Such all-oxide epitaxial structures are of current interest to better understand the underlying physics of pure spin current transport in heterostructures.

We are looking for an enthusiastic master student to work on this pure spin current physics related project. A crucial part of the thesis is the growth of oxide multilayers using laser-MBE under in-situ growth monitoring. The properties of these multilayers will then be investigated by structural, magnetic and magnetotransport techniques. As a next step, the tunability of relevant spin transport properties via the growth conditions will be analyzed

Materials for high energy density, solid-state batteries have been tremendously explored in the last decade. In particular, lithium-ion technology has attracted major interest. Among the many different types of batteries, the so-called polymer-based thin film batteries are very attractive as they can be incorporated into thin film devices. An inherent important part of such thin film lithium ion batteries is the membrane and solid-state polymer electrolyte membranes have attracted high attention in this respect. Lithium ions’ incorporation into solid-state polymer electrolyte membranes had shown a significant effect on both, the structure and properties, of the membranes in either the bulk or film format. The morphological reorganization and the thermodynamic properties of the solid-state polymer electrolyte membrane upon adding lithium salts and small molecules are the subjects of the experimental investigation. The polymer membranes will be prepared with printing. The structure and crystallinity of the lithium-doped membranes at different temperatures will be investigated with small/wide-angle X-ray scattering (SAXS/WAXS). The effects of morphology on the ionic conductivity of these ion-conducting membranes will be investigated using impedance spectroscopy. Aim of the present study is to increase conductivity with the help of small molecule additives, which can further improve the membrane morphology beyond the possibilities of the standard approach. Such high conductivity will be very beneficial for further downsizing of polymer-based thin film batteries.

Quantum optics is an extremely powerful approach towards quantum communication, quantum sensing, and quantum computing. In particular, quantum information stored in photons has very low decoherence and can be transmitted over large distances through optical fibers. To date, most experiments in quantum optics use optical tables full with mirrors and beam splitters that all have to be carefully aligned and stabilized. This may be good enough for initial demonstrations, but in order to bring quantum science into the realm of quantum technology, a more scalable approach is required.

With our expertise in making photonic chips using advanced nanofabrication, we are making putting these exciting quantum optics experiments on chips. Here, light is routed via optical waveguides. Furthermore, by bending a waveguide, one gets the equivalent of a free-space mirror; a beam splitter cube becomes a directional coupler and so on. By combining these elements, we can make the building block for e.g. an optical quantum computer. With that, the possibilities are almost unlimited.

For such large-scale optical quantum circuits we also want to incorporate single-photon sources, superconducting single-photon detectors, and optomechanical phase shifters. This all happens on a single chip. Making and characterizing the components is the first step and from there on, you are making more and more complex quantum chips. You will be doing the nanofabrication in the cleanroom, and then use our optical measurement setups to see how each device is performing. Depending on your preference, it may also be possible to add a modelling component to the project.

See http://www.groups.ph.tum.de/en/qtech/openings/ for a detailed description of this project.

In nature, quarks and gluons cannot exist as free particles. They are always confined into hadrons. Unfortunately, the equations of the strong interaction that governs the behavior of quarks and gluons cannot be directly solved at energy scales where hadrons form. Hence theoretical predictions of hadron properties such as their masses and decay modes are very difficult. This is in particular true for hadrons that are made of the three lightest quarks: „up“, „down“, and „strange“. Also on the experimental side much confusion exists on what concerns masses, decay widths, and the assignment of quantum numbers of some observed hadrons, let alone the interpretation of their internal structure.

Our group participates in the COMPASS experiment at CERN, where we study the production of mesons (hadrons with integer spin) in the scattering of a 190 GeV pion beam off a stationary proton target. The produced highly excited mesons have extremely short life times of the order of 10^-24 seconds and can hence be measured only via their decay products. Our group employs and develops mathematically involved statistical analysis tools in order to identify the produced mesons with high sensitivity and to measure their properties with high precision. We have recently found a new meson with surprising properties and also did groundbreaking work on precision measurements of the properties of the pion. This science is directly connected to the understanding of the strong force at large distances and low energies and the search for new forms of matter and therefore addresses one of the last open questions of the Standard Model.

This science project, involves the use of several state-of-the-art technologies:

• Building of analysis models in close collaboration with theorists
• Handling of very large data sets (several Petabytes)
• Elaborate data fitting with more than 1000 parameters
• Use of large computing clusters (200 cores at E18 + 2000 cores at LRZ/Excellence cluster)
• Software development to exploit new CPU/GPU technologies

In addition, we operate and maintain a large-scale scientific apparatus, which involves tasks like:

• Calibration of particle detectors
• Adaptation of large simulation codes

We offer thesis topics at various levels of difficulty, which cover a wide range of subjects in strong-interaction physics, statistics, and/or computer science. They include for example

• Data handling and event selection
• Simulation of high-energy scattering processes and detector response
• Estimation of model parameters from high-dimensional data
• Model building and model selection
• Parallelization of analysis software

You have the opportunity to perform your own science analysis, e.g. searching for new particles and determining their properties. The analysis work can start at different levels within the analysis chain: from the selection of a reaction process itself in order to study the feasibility of a full-fletched analysis up to the final fitting process leading to scientific publications. The topic can be chosen according to personal preference and interest. Thesis projects usually involve travels to CERN.

Experience in programming (C++, Python) is helpful, but not required.

Contact: Boris Grube , room PH1 3574, Tel. 089 289 12588

Whereas macroscopic sensors made of stimuli-responsive hydrogels are well established, in the nanoworld such sensors still face many challenges. Potential fields of application of such sensors extend from engineering to bioengineering and medicine, e.g. as nanosensors for the control of concentration of glucose for diabetes patients or as switchable surface in the frame of tissue engineering. In this experimental project smart hydrogels, made of stimuli-responsive hydrogels will be investigated. Hydrogel films with thicknesses of a few tens to some hundreds of nanometers and spontaneously deswell or swell due to external stimuli, like temperature or the concentrations of ions. The changes in thickness and in molecular interactions in swelling or collapsing hydrogels will be probed during the switching process by different lab-based techniques. A comprehensive understanding of the switching process can be achieved by complementary neutron scattering experiments at large scale facilities. The project will involve a literature review, preparation of hydrogels, as well as experimental investigations and interpretations of the repeated switching of the stimuli-responsive hydrogels.

The combination of ferromagnetic and superconducting materials leads to intriguing proximity effects at the interface of the two materials. The goal of this thesis is to investigate the spin transport of superconductor/ferromagnet interfaces and model the obtained results in the framework of proximity effects. To this end, we will use broadband ferromagnetic resonance and magnetoresistance effects to inject a spin current into the superconductor. This requires investigations at low temperatures around the critical temperature of the superconductor in large magnetic fields. For the superconductor/ferromagnet magnetoresistance effects, the magnetic field orientation dependence and its influence on the Andreev reflection contribution is the focus of this study.

We are looking for a talented master student to investigate spin transport in superconductor/ferromagnet heterostructures. The thesis deals with the fabrication of these heterostructures using our new UHV sputtering system and structuring of the blanket films with optical and electron beam lithography. In addition, characterization of theses heterostructures at low temperatures will be conducted in superconducting magnet cryostats. Here, high frequency spin dynamics as well magnetotransport studies will be conducted

Optomechanics provides extremely sensitive methods to measure the displacement of mechanical resonators. However, the forces are much smaller in optomechanics compared to those in nanoelectromechanical systems (NEMS). The goal of the project is to make, and measure opto-electromechanical devices which have strong electrostatic interactions. This includes the electrostatic spring effect where the resonance frequency depends strongly on the applied voltage. The next step is trying to measure the potential by measuring the ringdown of different mechanical modes. The devices will be made using advanced nanofabrication techniques such as electron beam lithography and reactive ion etching.

See http://www.groups.ph.tum.de/en/qtech/openings/ for a detailed description of this project.

The improvements of Silicon photo-multipliers (SiPM) over the last years qualify them as promising replacements for classical photo-multiplier tubes (PMT). This is particularly interesting for cases where the high voltages and large dimensions of PMTs are difficult to afford, such as for space applications. For the simplest version of gamma-ray detectors, a scintillator crystal read out by SiPMs, the size of the scintillator determines the sensitivity, and thus should stay large. This suggests an Anger camera principle as the most efficient way for a gamma-ray detector in space: a mosaic of sparsely distributed single-cell SiPMs instead of the coverage of the full scintillator area.

This Master thesis shall test and optimize a 5x5 cm^2 sized CeBr3 scintillator read out with a mosaic of SiPMs. Measurements of the spatial and spectral resolution as well as efficiency (noise) and power consumption are foreseen, and form the basic parameters for the trade-off study. The set-up has two potential applications: (i) in the ComPol Cubesat mission pursued within the Origins Cluster of Excellence, and (ii) the POLAR-2 gamma-ray burst polarisation mission developed within the SFB "Neutrinos and Dark Matter".

Interest in electronics and ASIC readout is required, and some background in astrophysics is advantegeous. The lab-work will be done at MPP Freimann, shared with Prof. S. Mertens group.
 
Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847

The broken inversion symmetry at the interface of thin film ferromagnets and normal metals with strong spin-orbit coupling can give rise to chiral magnetic order. These chiral magnetic materials show exotic magnetic properties such as a skyrmion lattice phase and have strong application potential for future spintronic devices. For these applications, a detailed understanding of the magnetization dynamics in these materials is required. The goal of this master thesis is to fabricate such thin film multilayer structures using sputter deposition techniques and analyze their dynamic magnetic properties using broadband ferromagnetic resonance spectroscopy.

We are looking for a highly motivated master student to carry out these experiments on interfacial effects in metallic multilayers. In this thesis you will work on the fabrication of these multilayer structures using UHV sputter deposition systems and subsequently determine their magnetic properties using broadband ferromagnetic resonance spectroscopy and SQUID magnetometry

Disorder has a drastic influence on transport properties. In the presence of a random potential, a system of electrons can become insulating; a phenomenon known as many-body localization (MBL) that has been envisioned by the Nobel laureate Phil Anderson. However, even beyond the vanishing transport such systems have very intriguing properties. For example, many-body localization describes an exotic state of matter, in which fundamental concepts of statistical mechanics break down. In this project we will explore these exciting aspects of many-body localization.

In 2011, a new solid lithium electrolyte was reported, featuring liquid-like Li-ion conduction in a crystalline solid matrix. The ultrafast room temperature transport of tetragonal Li10GeP2S12 (LGPS) with a conductivity of several mS/cm exceeds the values of most crystalline Li conductors by one order of magnitude. Accordingly, there has been a strong search in realizing LGPS-type materials based on the homologous elements Si and Sn. LXPS (X=Ge,Sn,Si) electrolytes appear in a tetragonal and orthorhombic modification. While the orthorhombic phase is an undesired inpurity in the LGPS electrolyte, orthorhombic LSPS leads to an enhancement of the conductivity. A possible explanation of the increased conductivity,
is an interplay of orthorombic and tetragonal LSPS, which distorts tetragonal LSPS. This distortion may lead to a favorable opening of Li-channels. The aim of this work is to investigate the effect of distortion on the materials conductivity for tetragonal LSPS. To do so a machine-learned force-field will be provided. The project will start with the construction of distorted LSPS structures and will then focus on Molecular Dynamics (MD) calculations for appropriate LSPS ensembles at finite temperatures. Finally, the conductivities will be calculated via the Nernst-Einstein relation.