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People currently working in our group:

Andris Gulans
Markus Scheidgen
Archana Manoharan
Christian Vorwerk
Claudia Draxl
Dmitrii Nabok
Helen Jurscha
Lorenzo Pardini
Maria Troppenz
Nora Illanes Salas
Olga Turkina
Pasquale Pavone
Santiago Rigamonti
Benedikt Hoock
Sven Lubeck
Eric Pierschel
Georg Huhs
Jungho Shin
Konstantin Lion
Martin Kuban
Sebastian Tillack
Axel Hübner
Ka Wai Lau
Saeideh Edalati-Boostan
Fabio Caruso
  • Andris Gulans
  • Markus Scheidgen
  • Archana Manoharan
  • Christian Vorwerk
  • Claudia Draxl
  • Dmitrii Nabok
  • Helen Jurscha
  • Lorenzo Pardini
  • Maria Troppenz
  • Nora Illanes Salas
  • Olga Turkina
  • Pasquale Pavone
  • Santiago Rigamonti
  • Benedikt Hoock
  • Sven Lubeck
  • Eric Pierschel
  • Georg Huhs
  • Jungho Shin
  • Konstantin Lion
  • Martin Kuban
  • Sebastian Tillack
  • Axel Hübner
  • Ka Wai Lau
  • Saeideh Edalati-Boostan
  • Fabio Caruso

Job opportunities

Master topics

Photon-energy dependence and final-state effects in photoemission spectroscopy

(contact: F. Caruso / C. Draxl)

Based on the photoelectric effects, angle-resolved photoemission spectroscopy (ARPES) provides information on the electronic structure of a system by measuring the kinetic energy of the electron which is emitted upon absorption of a photon. The photoemission intensity thereby typically exhibits a strong dependence on the photon energy and the polarization of light which is critical to achieve a realistic comparison between theory and experiment but most often negelcted in calculations.

Green function methods, such as the GW approximation, provide an ideal framework for a systematic and accurate theoretical description of ARPES experiments. Within this master project, the student will develop a theoretical and computational approach to predict the intensity of ARPES measurements on the energy and polarization of the probing photon. This will be accomplished by state-of-the-art methodology and it will provide numerous opportunities for collaboration with experimental groups.

 

Highly precise electronic band structures of metals

(contact: D. Nabok / C. Draxl)

Density-functional theory is the state of the art for computing materials properties without any parameters. Typical DFT functionals that describe the quantum-mechanical contributions to the electron-electron interaction are particularly well-suited for metals, such that DFT results are often interpreted as "real" band structures. Having high-resolution photoemission experiment in hand, we can assess the shortcomings of doing so. We propose corrections obtained by many-body perturbation theory to go beyond.

Within the master thesis, our GW code (D. Nabok, et al., Phys. Rev. B. 94, 035418 (2016).) should be used and slightly modifed to explore excitations in metallic systems.


Spectroscopic fingerprints of clathrate materials

(contact: C. Draxl)

Clathrate compounds are very promising materials in view of their excellent thermoelectric properties. They consist e.g., of Si cages which host heavier atoms like Ba and Sr. By substitution of Si, e.g. by Al, the physical properties can be tuned. Depending on the atomic site, the dopant may impact the material in a specific manner. In this thesis, we will explore, how the Al substitution affects excitation spectra.

Recent publications:
Maria Troppenz, Structural stability and electronic properties of the thermoelectric clathrates Ba8AlxSi46−x and Sr8AlxSi46−x, Master Thesis, Humboldt-Universität zu Berlin (2015).
M. Troppenz, S. Rigamonti, and C. Draxl, Predicting ground-state configurations and electronic properties of the thermoelectric clathrates Ba8AlxSi46-x and Sr8AlxSi46-x, Chem. Mater. 29, 2414 (2017).


Optical excitations in van der Waals heterostructures: Role of vacancies and defects

(contact: C. Draxl )

Van der Waals heterostructures are attracting increasing interest as potential materials for novel opto-electronic applications. They consist of single layers of two-dimensional materials stacked together through weak dispersive interactions. In this way, new exciting features may appear at the interfaces. Even more intriguing phenomena can be triggered by the presence of defects. The scope of this project is to study optical excitations graphene/h-BN heterostructures hosting vacancies and/or substitutional atoms.

 

Bachelor topics


Lattice vibrations in clathrate materials

(contact: S. Rigamonti / C. Draxl)

Clathrate compounds are very promising materials in view of their excellent thermoelectric properties. They consist e.g., of Si cages which host heavier atoms like Ba and Sr. By substitution of Si, the physical properties can be tuned. In this context, vibrational properties are important quantities that will be explored for various Al concentrations.

Recent publications:
Maria Troppenz, Structural stability and electronic properties of the thermoelectric clathrates Ba8AlxSi46−x and Sr8AlxSi46−x, Master Thesis, Humboldt-Universität zu Berlin (2015).
M. Troppenz, S. Rigamonti, and C. Draxl, Predicting ground-state configurations and electronic properties of the thermoelectric clathrates Ba8AlxSi46-x and Sr8AlxSi46-x, Chem. Mater. 29, 2414 (2017).

 

Reference data of electronic-structure theory

(contact: A. Gulans / C. Draxl)

There exist many ab-initio methods and computer packages to calculate ground-state properties, the electronic structure or various excitation spectra of materials. The exciting code, developed in the group, is able to provide results of highest precision. It is used to generate materials-science data that are valuable benchmarks for the international community.

Recent publications:
Kurt Lejaeghere et al., Reproducibility in density-functional theory calculations of solids, Science 351, aad3000 (2016); DOI: 10.1126/science.aad3000
A. Gulans, A. Kozhevnikov, and C. Draxl, Microhartree precision in density functional theory calculations, Phys. Rev. B 97, 161105(R) (2018).