Phase transitions beyond the Landau-Ginzburg-Wilson paradigm.

• Applicant: Professor Dr. Fakher Fakhry Assaad
• Subject Area: Theoretical Condensed Matter Physics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 493886309

In the Landau-Ginzburg-Wilson theory of phases and phase transitions, a state of matter is characterized by a local order parameter that is generically tied to the symmetry breaking properties of the phase: a complex number for superconductivity, a vector for magnetism. There are many phases of matter that escape this classification and that are at the forefront of research at the interface between the solid state, topology, and quantum information. They include symmetry protected topological phases such as topological insulators that are characterized by a topological invariant. Topologically ordered phases such as certain quantum spin liquids, exhibit geometry-dependent ground state degeneracy and hence cannot be described by a local order parameter. These phases can be detected only by using entanglement measures, and are uniquely defined by a sub-leading correction to the area law. Finally Kondo destruction phases remain challenging to characterize uniquely. Here, the only possible route is to use quantum information techniques based on the notion that Kondo destruction and heavy fermion phases exhibits different entanglement properties between the localized and itinerant degrees of freedom. In this project part, we will use state approximation free quantum Monte Carlo methods to address the following questions. (A) What are the unique signatures of the Kondo destruction transition from the perspective of entanglement? (B) Can we achieve a synergy between numerical calculations of thermodynamic properties of generalized Kitaev models and Kitaev materials such as RuCl3 ? (C) Can we provide experimentally realizable protocols to measure entanglement in correlated materials?

• DFG Programme: Research Grants
• International Connection: Austria
• Cooperation Partner: Professorin Dr. Silke Bühler-Paschen