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Technische Physik

Rudolf Gross

Forschungsgebiet

The research activities of the Walther-Meißner-Institute are focused on low temperature solid-state and condensed matter physics. The research program is devoted to both fundamental and applied research and also addresses materials science, thin film and nanotechnology aspects. With respect to basic research the main focus of the WMI is on

  • superconductivity and superfluidity,
  • magnetism, spin transport, and spin caloritronics,
  • quantum phenomena in mesoscopic systems and nanostructures,
  • and the general properties of metallic systems at low and very low temperatures.

The WMI also conducts applied research in the fields of

  • solid-state quantum information processing systems,
  • superconducting and spintronic devices,
  • oxide electronics,
  • multi-functional and multiferroic materials,
  • and the development of low and ultra low temperature systems and techniques.

With respect to materials science, thin film and nanotechnology the research program is focused on

  • the synthesis of superconducting and magnetic materials,,
  • the single crystal growth of oxide materials,
  • the thin film technology of complex oxide heterostructures including multi-functional and multiferroic material systems,
  • the fabrication of superconducting, magnetic, and hybrid nanostructures,
  • and the growth of self-organized molecular ad-layers.

The WMI also develops and operates systems and techniques for low and ultra-low temperature experiments. A recent development are dry mK-systems that can be operated without liquid helium by using a pulse-tube refrigerator for precooling. Meanwhile, these systems have been successfully commercialized by the company VeriCold Technologies GmbH at Ismaning, Germany, which meanwhile has been acquired by Oxford Instruments. As further typical examples we mention a nuclear demagnetization cryostat for temperature down to below 100µK, or very flexible dilution refrigerator inserts for temperatures down to about 20mK fitting into a 2inch bore. These systems have been engineered and fabricated at the WMI. Within the last years, several dilution refrigerators have been provided to other research groups for various low temperature experiments. The WMI also operates a helium liquifier with a capacity of more than 150.000 liters per year and supplies both Munich universities with liquid helium. To optimize the transfer of liquid helium into transport containers the WMI has developed a pumping system for liquid helium that is commercialized in collaboration with a company.

Adresse/Kontakt

Walther-Meißner-Straße 8
85748 Garching b. München
+49 89 289 14202
Fax: +49 89 289 14206

Mitarbeiterinnen und Mitarbeiter der Arbeitsgruppe

Professorinnen und Professoren

Mitarbeiterinnen und Mitarbeiter

Lehrangebot der Arbeitsgruppe

Lehrveranstaltungen mit Beteiligung der Arbeitsgruppe

Ausgeschriebene Angebote für Abschlussarbeiten an der Arbeitsgruppe

Electron spin dynamics in a strong coupling environment

Modern quantum circuits allow to study strong light-matter interaction in a variety of systems. This so-called strong-coupling regime requires that the coupling strength between the two subsystems exceeds their individual loss rates, rendering superconducting microwave resonators ideal due to their vanishingly low resistance. For this project, we use a paramagnetic spin ensemble of phosphorus donors in a silicon host as second system, as they show coherence and life-time in the order of seconds and minutes, respectively. The goal of this project is develop implement and develop pulse sequences to coherently control the spin ensemble and investigate the response of the coupled system.

We are looking for a highly motivated master student joining this project. The goal of your thesis is the implementation and development of adiabatic and optimal control pulse sequences for the investigation of the coherent dynamic of the coupled spin microwave system. Additionally, as microwave resonators play a vital role for the project, you will improve and tailor the existing microwave resonators for the specific needs of the project. The main goals of the project require simulation of the microwave circuits using finite element modelling, programming skills for the implementation of the pulse sequences and state of the art nano-fabrication techniques. 

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Hans-Gregor Hübl
Electron spin dynamics in a strong coupling environment

Modern quantum circuits allow to study strong light-matter interaction in a variety of systems. This so-called strong-coupling regime requires that the coupling strength between the two subsystems exceeds their individual loss rates, rendering superconducting microwave resonators ideal due to their vanishingly low resistance. For this project, we use a paramagnetic spin ensemble of phosphorus donors in a silicon host as second system, as they show coherence and life-time in the order of seconds and minutes, respectively. The goal of this project is develop implement and develop pulse sequences to coherently control the spin ensemble and investigate the response of the coupled system.

We are looking for a highly motivated master student joining this project. The goal of your thesis is the implementation and development of adiabatic and optimal control pulse sequences for the investigation of the coherent dynamic of the coupled spin microwave system. Additionally, as microwave resonators play a vital role for the project, you will improve and taylor the existing microwave resonators for the specific needs of the project. The main goals of the project require simulation of the microwave circuits using finite element modelling, programming skills for the implementation of the pulse squences and state of the art nano-fabrication techniques.

 
geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Engineering Magnetization Dynamics in a Magnetic Insulator

In magnetic resonance, a high frequency magnetic drive field is employed to excite the precessional motion of the magnetization of a magnet. Besides this fundamental excitation, where all spins are precessing in an orchestrated, collective motion, higher order magnetic resonance modes can be excited and investigated using broadband microwave spectroscopy techniques. Furthermore, as these properties rely on the „magnetic“ bandstructure of the material, they can also be tailored using nano-fabrication methods yielding engineered magnetic structures such as waveguides or resonators.

We are looking for a talented master student, who is eager to explore the different possibilities for tailoring the dynamic magnetic properties of yttrium iron garnet (YIG). The goal of your thesis is to design, fabricate and investigate tailored magnetic bandstructures in YIG, in particular also in freely suspended films. The thesis work involves simulation of the (magnetic) structures, advanced nano-patterning, as well as high frequency spectroscopy of the fabricated devices.

Contact: Hans.Huebl@wmi.badw.de, Mathias.Weiler@wmi.badw.deRudolf.Gross@wmi.badw.de

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Engineering topological magnetic phases in thin film heterostructures

In thin ferromagnetic films, the contribution from interface effects can give rise to novel magnetic properties not attainable in the bulk state of the ferromagnet. For example the magnetic anisotropy of the ferromagnet can be influenced by interfacing the ferromagnetic layer with other materials and allows to realize perpendicular magnetic anisotropy, which is now readily used in magnetic recording applications. In addition, the broken inversion symmetry at the interface leads to a Dzyaloshinskii-Moriya interaction, which allows to stabilize novel topological phases in the ferromagnetic layer (e.g. Skyrmionic lattice). The goal of this master thesis is to fabricate such thin film multilayer structures using sputter deposition techniques and analyze their magnetic properties with a focus on exploring pathways to tune the interfacial effects via different material combinations and deposition conditions.

A highly motivated master student is needed to carry out these experiments on interfacial effects in metallic multilayers. The thesis work will be split up into of the fabrication of these multilayer structures as well as the experimental study of these samples. An important aspect will be the fabrication of these multilayers using UHV sputter deposition systems. In addition, broadband ferromagnetic resonance spectroscopy and SQUID magnetometry are applied to investigate the magnetic properties of the thin film hetrostructures.

 
geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Entwicklung einer schnellen Rückkopplung für Quanteninformationsverarbeitungsprotokolle

Quantum information processing is based on rapid operations with fragile, and often short-lived, quantum states. In particular, superconducting nonlinear systems, such as quantum bits or Josephson parametric amplifiers, are offering outstanding capabilities in this field. In order to implement useful quantum protocols with these circuits, one often needs to perform local nonlinear operations on quantum states. One way to achieve the latter is to employ fast feedback schemes, when the state of interest is being quickly measured, and then, affected by an externally  generated signal, dependent on the measurement outcome. This allows one to implement many novel and important protocols such as quantum teleportation or quantum state stabilization. The particular implementation of is going to be based on FPGA-based real-time tomography measurements and a subsequent digital signal generation. To this end, one needs to program the FPGA and perform cryogenic  microwave measurements and data analysis in the framework of quantum physics.
Kategorie: Quantum information processing; Quantum microwaves; Feedback; FPGA programming.

Betreuer: Kirill.Fedorov@wmi.badw.de, Frank.Deppe@wmi.badw.de, Achim.Marx@wmi.badw.de , Rudolf.Gross@wmi.badw.de

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Entwicklung von experimentellen Millikelvin-Techniken für die supraleitende Quantentechnologie

Quantum science with superconducting circuits has recently been recognized as the most promising quantum technology hardware platform by industry (IBM, Google, various startups) and large efforts have been started to develop the underlying technologies. For this reason, 'quantum engineering' has become an important qualification for physicists. In this master thesis, you take one of the central experimental tool into operation: a cryostat operating only few hundreds of millikelvin above absolute zero. You then use this cryostat  to characterize low-loss superconducting quantum circuits.
Categoy: Cryogenics, Quantum information processing, Qunatum technology

Betreuer: Kirill.Fedorov@wmi.badw.de, Frank.Deppe@wmi.badw.de, Achim.Marx@wmi.badw.de , Rudolf.Gross@wmi.badw.de

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Herstellung und Charakterisierung von breitbandigen parametrischen Verstärkern auf der Basis von Josephson-Kontakten

Josephson parametric amplifiers (JPAs) are microwave devices based on nonlinear superconducting resonators. JPAs are important building blocks in experiments with quantum circuits as they allow for  quantum-limited amplification of incoming signals, which is crucial for fast and reliable operation of future quantum computers. A critical limitation of conventional JPAs is their relatively narrow  bandwidths. One possible way to increase the bandwidth, is to carefully engineer the resonator quality factor and the strength of its nonlinearity. Another, a more novel and difficult approach, is to use a microwave transmission line, instead of the resonator, strongly coupled to an ensemble of nonlinear elements provided by Josephson junctions. Such devices are also known under the name of traveling-wave Josephson parametric amplifiers (TWPA) and present a more flexible way of building of quantum-limited broadband microwave amplifiers. The main goal of this thesis is to design, fabricate, and characterize prototypes of broadband JPAs, and possibly TWPA. The fabrication is going to be based on the thin-film aluminum shadow evaporation process.                                                                                                                                                                                                             
Kategorie: Thin-film fabrication; Microwave measurements; Cryogenics.

Betreuer: Kirill.Fedorov@wmi.badw.de, Frank.Deppe@wmi.badw.de, Achim.Marx@wmi.badw.de , Rudolf.Gross@wmi.badw.de

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
High-field magnetotransport in an organic superconductor in proximity to the quantum spin-liquid Mott-insulating state

One of topical issues of the modern condensed matter physics is the interplay between superconducting and insulating instabilities of the normal metallic state in materials with strong electronic correlations. Organic metals and superconductors, thanks to their high crystal quality, simple conduction bands, and a great diversity of electronic states, offer a perfect laboratory for studying fundamental problems of the correlated electron physics. A member of the κ-(ET)2X family to be studied in this Master thesis is believed to represent 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 electronic properties, particularly, of correlation effects, in close proximity to the metal-insulator phase boundary. The position with respect to the phase boundary will be precisely tuned by applying quasi-hydrostatic pressure. Magnetoresistance and especially its quantum oscillations in strong magnetic fields will be used to probe the electronic properties of the system. Observation of the oscillations requires sufficiently low temperatures which will be achieved by use of a 3He cryostat (down to 0.4 K) and of a 3He-4He dilution refrigerator (down to below 100 mK). A part of the experiment will be done at the European Magnetic Field Laboratory in steady fields up to 30 T or in pulsed fields up to 80 T. The experimental results will be analyzed in comparison with recent theoretical predictions of correlation effects and violations of the Fermi-liquid behavior in proximity to the spin-liquid Mott-insulating state.

Physics: Correlated electron systems; metal-insulator transition; 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)

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Interaction between magnetic and conducting subsystems in molecular antiferromagnetic superconductors

Multifunctional materials combining nontrivial conducting and magnetic properties are one of hot topics in the modern condensed matter physics. Prominent examples are charge transfer salts of the organic donor BETS with anions containing a transition metal. They represent perfect multilayer structures of conducting and magnetic subsystems separated on a nanometer scale. The interplay between the two subsystems results in a variety of electronic and magnetic ground states depending on subtle chemical substitutions as well as on external magnetic field and pressure. The goal of this master thesis is a quantitative study of the interaction between the itinerant electrons and localized spins in the antiferromagnetic superconductors (BETS)2FeX4 with X = Cl, Br. To this end, comparative measurements of quantum oscillations in the magnetoresistance and magnetization will be carried out at strong magnetic fields, at temperatures down to 0.4 K. The results will be analyzed in terms of the exchange field dependent spin-splitting effect in a quasi-two-dimensional metal.

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)

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Korrelationsmessungen in einem Bose-Hubbard Dimer

Nonlinear superconducting quantum circuits allow one to model artificial matter in a bottom-up approach the laboratory. At the WMI, we have recently implemented a Bose-Hubbard dimer with tunable on-site nonlinearity. Your task will be to participate in correlation measurements of such structures. By means of this technique, which is a specialty of our group, you will investigate phase transitions of this system in the driven-dissipative regime.
Kategorie: Superconducting quantum circuits; Quantum simulation; Bose-Hubbard model

Betreuer: Kirill.Fedorov@wmi.badw.de, Frank.Deppe@wmi.badw.de, Achim.Marx@wmi.badw.de , Rudolf.Gross@wmi.badw.de

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Magnetization dynamics in chiral magnets

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. At WMI, we routinely use broadband magnetic resonance spectroscopy to study magnetization dynamics as a function of magnetic field, temperature and frequency in a wide range of different materials. Now, magnetization dynamics in thin film and bulk chiral magnets shall be explored, with a focus on novel resonance phenomena.

We are looking for a highly motivated and talented master student who is interested in joining our magnetization dynamics project. During your thesis, you will use state-of-the-art microwave equipment such as vector network analyzers as well as magnet cryostats and will work on the forefront of a rapidly developing scientific field.

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Magneto-acoustic torques

The magnetization dynamics of magnetic materials can be manipulated by acoustic waves through magnetoelastic coupling. Corresponding experiments using GHz-frequency surface acoustic waves are routinely performed at WMI and we have a broad range of spectroscopy tools - including optical and microwave techniques - at our disposal. Now, the interaction of acoustic waves and magnetization shall be studied 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 magneto-acoustics project. During your thesis, you will use state-of-the-art nanolithography tools and thin film deposition techniques to fabricate hybrid acoustic/magnetic devices. You will characterize these devices using both optical and microwave spectroscopy methods. 

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Nano-strings excited by magnetic torques

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. 

 
geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Pufferschichten für technische Leiter auf der Basis von Hochtemperatur-Supraleitern

The fabrication of ReBa2Cu3O7-δ (Re: rare earth element) (ReBCO) high temperature superconductor (HTS) based coated conductors requires the development of buffer layers (intermediate layers between a metal tape and a  superconductor). These buffer layers have to fulfill a list of requirements among which are chemical stability and  compatibility with adjacent films. Inclined substrate deposited MgO, developed by THEVA, is used as incident buffer  layer, because it creates a texture on metal substrate for the growth of HTS film and serves as a diffusion barrier for substrate elements. However, MgO is a hygroscopic material and has a high lattice mismatch with HTS, and therefore creates some technical issues for the consecutive deposition process. LaMnO3 is a perspective candidate as a terminal buffer layer due to its compatibility with MgO surfaces and is expected to provide a good template for growing ReBCO.

Depending on your qualification, following tasks will be performed during your work:
• Optimization of LaMnO3 deposition parameters
• Structural and compositional analysis (XRD, SEM, EDS, ICP)
• Deposition of GdBa2Cu3O7-δ HTS films on LaMnO3 buffered substrates
• Analysis of superconducting properties of the HTS films (Ic, Tc)

The experimental work of the master/bachelor thesis will be performed at THEVA GmbH, Ismaning. THEVA GmbH is an international, medium-sized high-tech company in the area of superconducting technology and special-purpose  systems for vacuum coating technology. For more than two decades THEVA has been developing process technologies for the manufacture of high temperature superconductors for power transmission and power  engineering. In our pilot production facility in Ismaning near Munich, we manufacture and distribute superconductors with a high power density.

Please send your application via e-mail with keywords "LMO bachelor" or "LMO master" to:
THEVA Dünnschichttechnik GmbH
Oleksiy Troshyn
Rote-Kreuz-Str. 8, 85737 Ismaning,
Tel.: 089 923346 0, E-Mail: hr@theva.com

geeignet als
  • Bachelorarbeit Physik
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Transmons play the strings: Coupled mechanical and superconducting quantum circuits for probing vibrational modes and the transfer of quantum states

Circuit nano-electro mechanics is a new field in the overlap region between solid-state physics and quantum optics with the aim of probing quantum mechanics in macroscopic mechanical structures. We employ superconducting circuits to address fundamental questions like, the preparation of phonon number states in the vibrational mode and the conversion of quantum states between the mechanical element and the microwave domain. The initial successful experiments of the group include hybrid devices based on superconducting transmon qubits, microwave resonators and mechanical nano-string resonators. You should aim at the next, important step to integrate the nanomechanical string resonator into the transmon qubit to experimentally realize a new type of interaction in light matter coupling. 

We are looking for a highly motivated master student joining this project. The goal of your thesis is the development of hybrid devices based on superconducting transmon qubits, nanomechanical string-resonators and superconducting microwave resonators as well as their spectroscopy. This includes the design and fabrication of these devices, where you will use state of the art simulation and nano-fabrication techniques. The second main aspect of your thesis is their investigation using highly sensitive microwave spectroscopy techniques in a low-temperature environment.

 
geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Transmons play the strings: Coupled mechanical and superconducting quantum circuits for probing vibrational modes and the transfer of quantum states

Circuit nano-electro mechanics is a new field in the overlap region between solid-state physics and quantum optics with the aim of probing quantum mechanics in macroscopic mechanical structures. We employ superconducting circuits to address fundamental questions like, the preparation of phonon number states in the vibrational mode and the conversion of quantum states between the mechanical element and the microwave domain. The initial successful experiments of the group include hybrid devices based on superconducting transmon qubits, microwave resonators and mechanical nano-string resonators. You should aim at the next, important step to integrate the nanomechanical string resonator into the transmon qubit to experimentally realize a new type of interaction in light matter coupling.

We are looking for a highly motivated master student joining this project. The goal of your thesis is the development of hybrid devices based on superconducting transmon qubits, nanomechanical string-resonators and superconducting microwave resonators as well as their spectroscopy. This includes the design and fabrication of these devices, where you will use state of the art simulation and nano-fabrication techniques. The second main aspect of your thesis is their investigation using highly sensitive microwave spectroscopy techniques in a low-temperature environment. 

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Hans-Gregor Hübl

Abgeschlossene und laufende Abschlussarbeiten an der Arbeitsgruppe

An Exploration of Quantum Magnetic Materials
Abschlussarbeit im Masterstudiengang Physics (Applied and Engineering Physics)
Themensteller(in): Rudolf Gross
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