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Accueil > Événements > Actualités > Seminars

Séminaire théorie

Cécile Répellin (MIT)
Stability of the spin-1/2 kagome ground state with breathing anisotropy
Lieu : Amphithéâtre, maison des Magistères,
le lundi 18 décembre 2017 à 11h00
Personne à contacter : Serge Florens ()

Quantum spin liquids (QSLs) are strongly correlated phases which cannot be characterized by a spontaneous symmetry breaking at zero temperature. Their exotic features (such as fractionalized excitations and topological properties) and the prospect of realizing them in frustrated magnets have aroused a lot of interest. The kagome lattice antiferromagnet is one the main model candidates which may realize a QSL. It poses a challenge to theorists and experimentalists alike: materials such as herbertsmithite can be approximated by this model but additional terms and disorder may change the nature of the ground state entirely. On the theoretical front, the ground state of the ideal model is generally admitted to be a QSL whose precise nature remains one of the most debated questions of the field, the (gapped) topological Z2 spin liquid and (gapless) dirac spin liquid being two of the strongest candidates. We study the spin-1/2 breathing (or trimerized) kagome lattice. In this variation of the kagome Heisenberg antiferromagnet (which appears in a recently synthesized vanadium compound), the spins belonging to upward and downward facing triangles have different coupling strengths. Beyond the experimental motivation, connecting the ideal kagome ground state to its fully trimerized counterpart may bring important insight into the nature of the kagome ground state, as strong coupling approaches have suggested the importance of the trimerized model as an effective model capturing most low energy degrees of freedom. Using DMRG and exact diagonalizations, we show the large stability of the kagome ground state upon introducing the breathing anisotropy. Exploration of the entanglement properties of the ground state confirm this picture, and reveal the persistence of signatures of Dirac excitations even for relatively large breathing anisotropy. Finally, we closely examine the limit of strong breathing anisotropy and find indications of a transition to a nematic phase.


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