Periodic Reporting for period 1 - 2DMAGICS (Two-dimensional magnetism in correlated systems)
Période du rapport: 2020-12-01 au 2022-11-30
Using materials from this class for technological applications requires an accurate theoretical understanding and, ideally, prediction of their properties. These materials are characterized by a complex interplay between spin-orbit coupling and strong non-local Coulomb correlations, which represents an outstanding challenge for a consistent theoretical description. Within 2DMAGICS the proposed low-dimensional systems have been studied using a combination of already existing theoretical approaches and novel methods. The latter were developed in the framework of the project in order to provide a realistic multiscale description of many-body effects beyond the state-of-the-art. This allowed 2DMAGICS to resolve a number of fundamental issues in the general field of magnetism and, based on these accomplishments, to achieve an accurate description and prediction of various properties of realistic materials.
A multi-mode generalization of the fluctuating field method that allows one to describe dynamical symmetry breaking towards a magnetically ordered phase has been introduced. The free energy of a prototypical one-dimensional molecule with strong magnetic fluctuations has been calculated. The results have been published in Phys. Rev. B 105, 035118 (2022). Further, a multi-channel extension of this method was developed. The improved method allows one to describe the interplay between the leading collective electronic fluctuations in the system numerically exactly. The multi-channel fluctuating field approach has been applied to an electronic model with long-range Coulomb interactions in order to investigate the competition between the charge- and spin-density wave instabilities that emerge in the system. The results of this study have been submitted to a peer reviewed journal for publication.
A novel method, dubbed D-TRILEX, for describing collective electronic effects in realistic multi-orbital systems has been developed and implemented as a program package. The method was benchmarked against existing exact solutions in the single- and multi-orbital cases. The results and description of the D-TRILEX program package are published in Phys. Rev. B 103, 245123 (2021) and in SciPost Phys. 13, 036 (2022).
The D-TRILEX method has been applied to study many-body effects in two-dimensional indium selenide (InSe), a material with unique characteristics of the electronic spectrum. We have demonstrated that the monolayer phase of InSe is a rare example of a system, where collective electronic fluctuations lead to the formation of exotic states of matter, such as coexisting charge density wave and ferromagnetic orderings. The results of this study have been published in npj Comput. Mater. 8, 118 (2022).
The magnetic susceptibilities for a system of lead adatoms on a silicon surface have been calculated using the D-TRILEX method. This allowed us to investigate the temperature vs doping level phase diagram of the material. As a result, we have found several charge- and spin-density wave phases, a signature of which has recently been observed experimentally. The results of this study have been submitted to a peer reviewed journal for publication.
While working on the project the PI obtained a permanent researcher position at CNRS, France. The PI regularly gives scientific seminars and also participates in several collaborations at the host institution (Ecole Polytechnique, France). To disseminate the results of the research, the PI gave invited talks in scientific groups at University Paris-Saclay, University of Manchester, University of Hamburg, and at the TRIQS meeting at College de France (Paris, France). The PI also attended the GDR 2426 Quantum Mesoscopic Physics meeting (Aussois, France) and the Psi-k conference (Lausanne, Switzerland) with poster presentations. Results of the research are regularly prepared for scientific publication. In addition, the PI contributed to a review paper entitled “Quantitative theory of magnetic interactions in solids”.