Tutorial 11. Correlation and Topology in Flat Band Quantum Materials
ANCILLARYEVENT · MAR-11T · ID: MAR-11T
Strongly correlated quantum materials display a rich array of unconventional properties that often require the development of new theoretical frameworks for proper understanding. To advance in this field, it is highly desirable to realize tunable systems that inherently support strong electron correlations. Recent studies have shown that active flat electronic bands, such as originating from geometric frustration, provide a promising platform for realizing such strongly correlated behavior [1]. These systems exhibit flat bands in the close vicinity of the Fermi energy, leading to a large density of states that allows the Coulomb interaction to readily induce a host of instabilities. Accordingly, they feature amplified quantum fluctuations that drive novel quantum behavior. Importantly, a set of bulk materials with frustrated lattices have been discovered in this context. They are especially advantageous compared to the two-dimensional moiré systems in that a whole array of physical properties can be experimentally determined at energy and temperature scales readily accessible by established probes. The correlated flat bands in such systems are also topological in nature – catalyzing the development of a new theoretical framework that describes the strong correlation effects in the presence of topological obstruction, with a key ingredient that strong correlations pin the emergent flat bands to the Fermi energy [2,3]. This surprising feature leads to a variety of novel phenomena which have been experimentally observed, including strange metallicity [1,3-6], unconventional superconductivity [7], and correlated topology [1]. The tutorial will bring together experts from both theory and experiment who are leading the advances. Topics to be discussed include new design principles for emergent flat bands in quantum materials, latest progress on identifying new quantum phases in topological flat bands, topology driven by strong correlations, and new correlation physics enabled by topology. Price:
Presenters:
Experimental:
Theoretical:
Key recent references:
[1] Flat bands, strange metals and the Kondo effect. Nat. Rev. Mater. 9, 509 (2024).
[2] Coupled topological flat and wide bands: Quasiparticle formation and destruction. Sci. Adv. 9, eadg0028 (2023).
[3] Non-Fermi liquid behaviour in a correlated flat-band pyrochlore lattice. Nat. Phys. 20, 603 (2024).
[4] Hopping frustration-induced flat band and strange metallicity in a kagome metal. Nat. Phys. 20, 610 (2024).
[5] Quantum critical metals and loss of quasiparticles. Nat. Phys. 20, 1863 (2024).
[6] Resolving the Kagome Origin of the Strange Metallicity in Ni3In. arXiv: 2503.09704.
[7] Superconductivity under pressure in a chromium-based kagome metal. Nature 632, 1032 (2024).