Description du projet
Des modèles perfectionnés pour étudier le comportement des métaux exotiques
Le modèle du liquide de Fermi permet de prédire les propriétés des métaux classiques à des températures suffisamment basses. Il existe cependant une classe de liquides non-Fermi ou de métaux exotiques qui s’écartent de ce modèle et présentent des propriétés extraordinaires. Les exemples les plus marquants sont notamment certains composés de fermions lourds et les semi-conducteurs à haute température. Financé par le programme Actions Marie Skłodowska-Curie, le projet EXOMETALS a pour vocation de construire des modèles d’impuretés quantiques avancés qui décrivent ce type de métaux. Ces modèles pourraient décrire les interactions entre les degrés de liberté locaux (spin) des particules et les électrons de conduction environnants. L’objectif ultime du projet est de créer de nouveaux états de la matière dans les matériaux en vrac et d’explorer le comportement de ces métaux exotiques dans les dispositifs à points quantiques.
Objectif
The standard theory of electrons in metals, Landau’s Fermi liquid theory from 1956 has been very successful in predicting the low-temperature properties of many metals. Its greatest success was its ability to describe many heavy fermion metals, whose name comes from the huge apparent masses acquired by their conduction electrons. However increasingly many metals have been synthesized where Fermi-liquid predictions fail. They are called non-Fermi liquid (NFL) or exotic metals. Prominent examples are certain heavy fermion compounds and high-temperature superconductors. These materials are of interest because of the emergence of new properties that could be used in future technologies. In most cases NFL behaviors lack the understanding, as only a handful of solvable, microscopic models describe NFL phenomena. To make strides I will construct a novel class of NFL quantum impurity models. Quantum impurity models describe the interaction between local degrees of freedom, like a spin, and the surrounding conduction electrons. The simplest NFL quantum impurity model was considered to be the so-called two-channel Kondo model (2CKM). One of the new quantum impurity models—which I call the one-and-a-half-channel Kondo model and whose low-energy solution gives the topological Kondo effect—has less degrees of freedom and is, in this sense, simpler than the 2CKM, yet it also exhibits NFL behavior. Generally, this new family of NFL quantum impurity models includes all those overscreened Kondo-type models where the number of conduction electron species are not integer multiples of the number of impurity states. I will study the new quantum impurity models using Wilson’s numerical renormalization group method (recognized by the 1982 Nobel Prize). My further aims are to experimentally realize the corresponding NFL behavior, i.e. create new states of matter in bulk materials, and also to theoretically explore alternative realizations of the novel NFL physics in quantum dot devices.
Champ scientifique
Mots‑clés
Programme(s)
Régime de financement
MSCA-IF - Marie Skłodowska-Curie Individual Fellowships (IF)Coordinateur
EH8 9YL Edinburgh
Royaume-Uni