Strongly Correlated Systems

The Strongly Correlated Systems (FFC) group focuses on the theoretical study of quantum many-body systems, especially those with strong correlations and magnetic frustration. The group is dedicated to understanding the complex behaviors of quantum models and materials that do not follow the classical regime, often leading to the emergence of exotic phases of matter such as quantum spin liquids, topological insulators, many-body localization, skymions, and various other strongly correlated unconventional states. The FFC group maintains strong collaborations with experimental groups and other theoretical teams worldwide, contributing to a broad network of research in quantum condensed matter physics. Their work not only advances the fundamental understanding of quantum materials, but also has implications for emerging technologies such as quantum computing and quantum information science.

Research Areas

The work of the FFC group spans several cutting-edge topics in condensed matter physics, with an emphasis on quantum magnetism, disorder, and strongly correlated systems. These systems are characterized by the intricate interplay between quantum mechanics and many-body interactions, leading to highly non-trivial ground states and low-temperature phases. Some key research areas are:

 

  • Quantum magnetism and frustration
    The group studies magnetic systems where the interactions between spins lead to competing tendencies, resulting in frustrated configurations that prevent the system from settling into a conventional magnetic order, leading to novel quantum states, including spin liquids where long-range magnetic order is absent even at absolute zero temperature.

 

  • Strongly correlated quantum systems
    In materials with strong electron-electron interactions (cuprates, organic conductors, iron pnictides, etc…), classical descriptions break down, giving rise to phenomena such as unconventional superconductivity or magnetic textures (like skymions). Moreover, the role of quantum fluctuations is very pronounced in one-dimensional correlated quantum systems, where advanced analytic and numerical techniques are needed to go beyond mean-field theories.

 

  • Topological phases.
    The group is also active in the study of topologically-ordered systems and symmetry-protected topological phases, where quantum phases are distinguished not by local order parameters but by global topological invariants. This area is crucial for understanding quantum computing and topological quantum computing.

 

  • Disorder and Many-Body Localization
    A key area of the group’s work is the study of disordered quantum systems, especially in the context of many-body localization. MBL is a fascinating phenomenon in which disorder can prevent thermalization in an interacting quantum system, leading to non-ergodic behavior and the persistence of quantum coherence at infinite times.

 

Methods
The FFC group uses a combination of analytical techniques and state-of-the-art numerical methods to study these systems. Analytical approaches include effective field theories and renormalization group techniques, which provide a conceptual framework for understanding low-energy excitations and phase transitions in quantum materials. Numerically, the group is skilled in exact diagonalization, quantum Monte Carlo simulations, tensor network approaches, and density matrix renormalization group. These tools allow them to handle both large systems and complicated quantum phases that are beyond the reach of simple analytical calculations.

Team members

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