Placement Information
Year you started your placement
2012
Placement period
May – August, September – December
Supervisor’s name
Christian Ast
Project Details
Overview
During the past five months here at the Max Planck Institute for Solid State Research, I have been working with surface alloys and studying various affects such as Anderson Localization in their context. At the beginning of my time here, I followed a former PhD student in his task of collecting STM (Scanning Tunneling Microscope) data of a specific surface alloy. This surface alloy was made by evaporating Bismuth/Antimony particles onto a Silver(111) surface in the form of a hexagonal lattice. Having collected this data and looking at experimental measurements of the local density of states, I started developing a simulation program on MATLAB with the goal of seeing how accurately the theoretical models fit the observations. The program in its current state will take an arrangement of atoms as an input and then will measure the Hamiltonian of the system using the tight bonding model. The Hamiltonian measurements take various on-site and hopping energy terms into account including spins and external magnetic fields. After the Hamiltonian is calculated, the eigenvalues and eigenvectors of the system can be determined. These represent the wave functions at various energies. From this, the probability densities at various energies are determined and are compared to the experiment. Taking the Fourier transforms of the wave functions, we get the momentum distribution of electrons in reciprocal space. By plotting these in the lattice Brilluoin zone, we extract the band structure. This gives us much information about the lattice.
With this simulation at hand, the effects of changing various parameters on the band structure can be studied. The concentrations of the atoms in the alloy, the on-site atomic potentials, the hopping energies, among other factors, are being looked at. Going forward, I am going to be using Green functions to calculate the self-energy of impurities and characterize its dependence on a number of the above-mentioned factors.
Project objectives
My goal in this project is to determine the self-energies of impurities as a function of the on-site energies of the atoms and the concentrations at which they are present in the surface alloy. Beyond providing a refined theoretical understanding, this information will have implications in the interpretation of photo-emission spectroscopy data.
Project status
Completed
My Co-op Experience at MPI
Why did you apply for a placement with Max Planck Institute?
My motivation for applying for a placement with the Max Planck Institute was two fold. First, I wanted to work in a research laboratory where I would be able to study the fundamental physics we learn in our classes on a personal level and in an in-depth project. The Max Planck Institute seemed to be the realization of this vision. It is one of the worlds most respected and acclaimed research centers. The scientists working here have consistently been engaged in interesting fundamental research, and have year after year come up with remarkable results that are shared in high-impact publications with the world scientific community. Doing an 8 month co-op term here for me was equivalent to teaming up with highly motivated and knowledgeable individuals to conduct experiments exploring unknown scientific territory.
Second, I found the prospect of living in another country and culture, learning another language, meeting people from around the world, and making memories travelling around Europe enticing. Applying to come to the Max Planck Institute for Solid State Research in Stuttgart, Germany, was at this point a matter of common sense. The experience had everything I was looking for in this co-op term.
What recommendations do you have for students who wish to participate in MPI-UBC exchange program?
The opportunity to come to the Max Planck Institute is a unique one, and one should make the most of it. In an environment where you are surrounded by Master students, PhDs, Post-docs, and seasoned scientists working on their own passions and fields of interest, you have to take initiative and work hard. There is a saying that goes: “you determine your own level of involvement”. As an undergraduate student starting out in this environment, you have to prove yourself, your ability to learn and adapt, and your eagerness to pick up new projects. In this way, your responsibilities will grow and you will become an integral member of the tight-knit research community. I believe this is how you will get the full worth out of a co-op term at the Max Planck Institute.
Tell us about your travels and cultural experiences in Germany and the rest of the Europe
Living in Europe has been quite an experience. Every country has its own unique culture, history, and traditions, and with the help of trains and low-cost airlines one can explore freely. Having Stuttgart as a home base for the past five months, I have been able to visit cities and places that have captured my imagination me since childhood. Some of the highlights have been: watching the Italy-Spain Group C match of the UEFA Football championships in a bar in Florence, Italy. Reuniting with a high-school friend in Prague and going to a five-story nightclub on the Vltava riverbank at nighttime. Driving a Smart car from one ancient castle to another in the Bamberg country-side in northern Bavaria for a whole day and taking breaks for some short hikes. Ordering “gambas” or fresh prawns by mistake in Seville and being slightly scared of eating them. The list goes on. These have been incredible times and I will look back on them warmly for the rest of my life.
