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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
Elektrisch gesteuerter Magnontransport in magnetisch geordneten Isolatoren

Angular momentum transport in magnetically ordered insulators is carried by magnetic excitation quanta in contrast to magnetic conductors, where mobile charge carrier also carry angular momentum. In magnetically ordered insulator/normal metal hybrids it is possible to study the transport of angular momentum by all-electrical means via the spin Hall and inverse spin Hall effect in the normal metal. The focus of this project is the investigation of possibilities to manipulate the angular momentum transport in the magnetically ordered insulator by electrical means and by finite size effects. In addition, another goal is the enhancement of the sensitivity of the currently existing measurement setup and the realization of new measurement protocols in hard- and software.

An ambitious master student with good analytical skills is required to carry out these experiments on all-electrical magnon transport. One part of the thesis is the fabrication of nanometer sized devices for the experiments via electron beam lithography and UHV sputtering. The properties of these devices will be analyzed using magnetotransport experiments in superconducting magnet cryostats. Another important aspect is the realization of more sophisticated measurement methods, aiming for a enhancement in sensitivity, a better signal-to-noise ratios and a higher versatility of the measurement protocols

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
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
Manipulation von Spin-Wellen durch Spin-Bahn-Drehmomente

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.

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
Oxidische Heterostrukturen für Experimenten mit reinen Spinströmen

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

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.

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Gross
Topologische magnetische Phasen in Dünnschicht-Heterostrukturen

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. The thesis work will be split up into of the fabrication of these multilayer structures using UHV sputter deposition systems and determining their magnetic properties by broadband ferromagnetic resonance spectroscopy and SQUID magnetometry.

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): 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
Untersuchung von Fluktuationen und Spin Anregungen in magnetisch entzwillingtem Eu122

Eu122 is a member of the iron-based pnictides which exhibit magnetism and superconductivity in close proximity. By slightly changing the stoichiometry the phases can be controlled. In wide ranges of the phase diagram fluctuations exist indicating a high susceptibility to perturbations and are therefore considered important for the formation of superconductivity. In this thesis magnetic ordering and the related fluctuation shall be studied by light scattering in the parent compound. For better understanding the magnetic anisotropy monocrystalline samples are required. The de-twinning process can be achieved here by the application af a magnetic field at low temperature rather than mechanical stress. After switching off the field intrinsic and extrinsic properties can be observed separately.

geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Rudolf Hackl

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
A Transport Laser with Shape and Amplitude Control for Ultracold Strontium Atoms
Abschlussarbeit im Masterstudiengang Physics (Applied and Engineering Physics)
Themensteller(in): Rudolf Gross
Quantum Process Tomography of a 3D Quantum Memory
Abschlussarbeit im Masterstudiengang Physics (Applied and Engineering Physics)
Themensteller(in): Rudolf Gross
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