I currently propose two master internships (M2) in theory of condensed matter, cosupervised by two colleagues at LPMMC. To formally apply, please send me a brief email presenting yourself, including your CV, your grades of the previous year/semester and any reports you made for previous internships. If you have recommendation letters, it is a plus, but not mandatory.
Important note: due to administrative constraints, non-EU applications need to be done at least two months before the beginning of the internship. For EU applications, administration is far less strict but at least a month is needed to set-up the contracts.
Feel free to send me an email should you be interested by something else than what is presented below (or a PhD/postdoc position). I am always happy to talk about physics.
Numerical simulations of SU(N) spin chains and ladders
Codirector: Pierre Nataf
Large-spin models have recently gained significant attention due to experimental breakthroughs in cold atom systems. These setups enable highly controlled experiments that simulate complex theoretical models. However, large-spin models present considerable challenges for numerical modeling. The large spin dimensions and intricate symmetries of these systems make simulations extremely difficult, and standard methods often fall short, failing to access certain experimental regimes of interest.
In this context, an alternative approach was recently proposed by one of the project supervisors. This method bypasses the calculation of Clebsch-Gordan coefficients, thereby overcoming the limitations of traditional approaches. Given its demonstrated potential, there are now several promising avenues for further development. The proposed internship will explore these avenues in multiple stages. Initially, the student will delve into group theory, with a particular focus on SU(N) group representations, which are crucial for modeling large-spin systems. A solid grasp of these concepts is essential for the later stages of the project.
Subsequently, the student will implement a numerical method (exact diagonalization) to model quantum systems with high accuracy. Several theoretical models are under consideration, including variants of Heisenberg chains and ladders, where analytical approaches fail to provide clear predictions.
Finally, with a view towards continuing in a PhD, the student will explore tensor network methods. These have become one of the most powerful and efficient tools for modeling low-dimensional quantum systems. Tensor networks are particularly well-suited to simulating one-dimensional systems like spin chains, offering unmatched precision in capturing their fundamental properties. Our goal is to adapt existing algorithms to integrate this new computational approach.
Exploring Spin-Orbit Coupling in Quantum Hall Systems
Codirector: Thierry Champel
The quantum Hall effect (QHE) has long been a key area of research in condensed matter physics, exemplifying the role of topology in quantum mechanics. In QHE systems, the Hall conductance becomes quantized with significant applications in quantum metrology. The fractional quantum Hall effect, which arises due to electron-electron interactions, leads to the creation of exotic quasi-particles with fractional charge and statistics that are neither fermionic nor bosonic.
Recent experimental progress [1] has unveiled numerous fractional Hall plateaus, particularly in bilayer systems like graphene or double quantum wells. These bilayer structures introduce new complexities [2] due to strong interlayer interactions. Spin-orbit coupling can also be present – or engineered – in these materials. The spin-orbit coupling complicates the traditional picture of spin being a good quantum number and alters the nature of the QHE states [3]. Near Landau level crossings, these effects are further amplified, leading to rich and intricate physics [4] that demands theoretical attention.
This internship project will focus on the effects of spin-orbit coupling on integer QHE systems. It will begin by analyzing how spin-orbit coupling modifies the wavefunctions and edge states of non-interacting electrons in a single Landau level in the presence of trapping potentials. The second phase will consider Landau level crossings effects in bilayer structures and address electron interactions through a mean-field Hartree-Fock approach. Combining both analytical and numerical work, this research will contribute to a better understanding of topological phases. Long-term (PhD) goals include extending this analysis to study transport and disorder effects, light-matter coupling to a QED cavity, or a more precise numerical treatments of interactions to study fractional phases.
[1] K. Huang et al, Phys. Rev. X 12, 031019 (2022)
[2] E. McCann et al, Rep. Prog. Phys. 76 056503 (2013)
[3] Y. Xing et al., Phys. Rev. B 77, 114346 (2008)
[4] P. Nataf et al., Phys. Rev. Lett. 123, 207402 (2019)