In the field of condensed matter physics, a groundbreaking theorem known as Luttinger’s theorem has been instrumental in understanding the behavior of particles within a system. Introduced by Joaquin Luttinger in 1960, this theorem establishes a connection between the total number of particles a system can accommodate and its behavior under low-energy excitations. While initially believed to hold true in all scenarios, recent research has revealed the failure of Luttinger’s theorem in certain instances of strongly correlated phases of matter.
The failure of Luttinger’s theorem in specific and exotic instances of strongly correlated phases of matter has garnered significant attention within the scientific community. These exceptions have had profound implications for our understanding of quantum matter and have opened up new avenues of research in condensed matter physics. The discrepancies observed in these scenarios have sparked intense research efforts to comprehend the underlying mechanisms responsible for the failure of Luttinger’s theorem.
Parallel to the investigations into the failure of Luttinger’s theorem, researchers have dedicated substantial efforts to the classification and characterization of correlated insulating states. These states of matter have distinct transport properties and have been a subject of interest due to their potential applications in various technological advancements. A significant milestone in the classification of insulating states came with the discovery that a single integer, known as the Ishikawa-Matsuyama invariant, could fully capture the transport properties of a broad class of topological insulators.
However, recent theoretical advancements have revealed the existence of exotic models of correlated insulators that do not adhere to the classification based solely on the Ishikawa-Matsuyama invariant. These models defy the simple prescription provided by the invariant for classifying insulating states in the presence of strong interactions. Given this, researchers have identified the need for corrections to the Ishikawa-Matsuyama invariant in these peculiar settings.
In a groundbreaking research article published in Physical Review Letters, Lucila Peralta Gavensky and Nathan Goldman from ULB, together with Subir Sachdev from Harvard, have unveiled a fundamental relation connecting the failure of Luttinger’s theorem and the classification of insulating states of matter. Their work demonstrates that the Ishikawa-Matsuyama invariant effectively characterizes correlated insulators when Luttinger’s theorem is satisfied. However, when Luttinger’s theorem is violated, the topological invariant falls short in labeling the correlated phases accurately. The authors have provided explicit expressions for the necessary corrections to the Ishikawa-Matsuyama invariant, relying on relevant physical quantities.
This remarkable connection between Luttinger’s theorem and the topological classification of quantum matter offers new insights into the emergence of exotic phenomena in strongly correlated quantum matter. By understanding the failure of Luttinger’s theorem and its connection to the classification of correlated insulating states, researchers can make significant strides in unraveling the mysteries of quantum matter and pushing the boundaries of condensed matter physics. The findings from this research serve as a stepping stone towards a deeper understanding of the complex behavior exhibited by quantum systems.