PhD position in Quantum Many-body Theory with Focus on Superfluidity/superconductivity in Flat Band Systems in the Presence of Disorder
Aalto University is a community of bold thinkers where science and art meet technology and business. We are committed to identifying and solving grand societal challenges and building an innovative future. Aalto University has six schools with nearly 11 000 students and nearly 400 professors. Our campuses are located in Espoo and Helsinki, Finland.
The newly formed group lead by Academy Research Fellow Sebastiano Peotta is looking for one PhD student on quantum many-body theory. This position is part of the project “Superfluidity, topology and disorder in lattice models with flat bands (SuperFlat)” funded by the Academy of Finland. In your research work, you will tackle the problem of how disorder affects the transport properties of a superfluid phase occurring in a flat band (a so-called flat band superfluid). An example of a flat band superfluid is the recently discovered magic angle-twisted bilayer graphene, which has attracted enormous interest in the condensed matter physics community, therefore this is a very timely research topic.
The workplace is located on the university campus near Helsinki and offers a motivating and state-of-the-art research environment. The research group is part of the Department of Applied Physics at Aalto University. For more information you can refer to website of the Department (https://www.aalto.fi/en/department-of-applied-physics) and the homepage of the principal investigator (https://users.aalto.fi/~peottas1/).
Research topics and major responsibilities
Electronic bands with very narrow bandwidth, also called flat bands or quasi-flat bands, are a viable route to increase the critical temperature of the superconducting transition, as proposed in 2011 by researchers working at Aalto University. A new class of materials with quasi-flat bands has been recently identified in twisted van der Waals materials, of which twisted bilayer graphene is just the first example. Lattice models with flat bands have also been realized with ultracold gas quantum simulators in recent years.
Disorder in the form of lattice imperfections and impurities is unavoidable in condensed matter systems and can also be introduced in a controlled way in ultracold gas systems. In your research you will investigate how disorder affects a flat band superfluid, in particular what is the effect of disorder on the superfluid weight. The superfluid weight is an observable quantifying the ability of a superfluid/superconductor to sustain a nondissipative current. It has also been shown that the superfluid weight is connected to the geometric and topological properties of the band structure [S. Peotta and P. Törmä, Nature Communications 6, 8944 (2015)]. Your goal will be to unveil the interplay between disorder and topology of the band structure, which is expected to be particularly interesting and rich in flat bands, as suggested by these previous results.
The aim is also to provide immediate experimental verification of the theoretical results obtained during the project using as a preferred platform ultracold gases in optical lattices, taking advantage of ongoing collaborations with leading experimental groups in Switzerland and Japan. Therefore you will have the chance to work in close contact with these groups and have your ideas implemented in state of the art experimental facilities.
We are looking for an outstanding candidate with a good background in quantum physics, mastering both analytical and numerical skills. The candidate should hold a Master’s degree in physics or equivalent. The motivation to learn about topics such as topological properties of condensed matter systems, quantum many-body theory, many-body localization, macroscopic quantum phenomena such as superconductivity and superfluidity and realizations thereof in ultracold gas systems is an essential prerequisite. Any previous exposure to any of these topics is considered an advantage.
During the doctoral studies the PhD student will learn and use advanced methods to tackle the quantum many-body problem, for instance numerical techniques such as exact diagonalization and density matrix renormalization group, therefore some experience with computational methods in physics is also an important asset.
The ability to collaborate and interact with other researchers and research communities are important. You should have good communication skills and ability to work independently towards the goals of the project. This will be especially important for effectively developing the collaborations with other theoretical groups within the Department of Applied Physics and also with both theoretical and experimental groups at the international level.
The position will be filled for a four-year period between 2020 and 2025. The position is subject to a mid-term evaluation at the end of the second year, as required by the Department of Applied Physics. At the end the candidate is expected to successfully complete the doctoral dissertation at Aalto University. The salary will be based on the salary system of Finnish universities. The gross starting salary amounts approx. to 2530 €/month.
Candidates should send the following documents (all in English) as a single pdf-file.
- Motivation letter
- List of publications if any
- Copy of the Master’s thesis
- Master’s degree certificate
- Contact information of two references, possibly including the Master’s thesis supervisor
Apply through the link “Apply now !” at the bottom of the page
The deadline for applications is 20th September 2020, but the position will remain open until filled. For questions, please contact Dr. Sebastiano Peotta (see contact information below). Aalto University reserves the right for justified reasons to leave the position open, to extend the application period, reopen the application process, and to consider candidates who have not submitted applications during the application period.
As a living and work environment, Finland is consistently ranked highly in quality-of-life and competitiveness studies. It is the happiest place in the world according to a 2019 World Happiness Report. Finland is the most stable, freest and safest country in the world in 2019. Helsinki is the third best city in the world to live in according to a 2016 report by Metropolis magazine. The air in Finland is the cleanest in the world and the food cleanest in Europe. Finland has also been ranked the 10th in the Global Competitiveness Index 2017-2018 of the World Economic Forum. And Finns drink the most coffee per capita in the world; by the way, coffee is free at our institute! For sources see https://www.stat.fi/ajk/satavuotiassuomi/suomimaailmankarjessa_en.html and http://www.stat.fi/tup/tilastokirjasto/itsenaisyyspaiva-2019_en.html
Aalto University offers support for moving of international staff to Finland. Some useful information is available at: https://www.aalto.fi/en/careers-at-aalto/for-international-staff