Agenda

Prochain séminaire LANEF/Matériaux Quantiques :

Jeudi 13 juin 2024 à 14h00

Chisa Hotta (University of Tokyo)

“ Quantum Lifshitz critical point and gapless nematic singlet phase of the spin 1/2 model featuring YbCuS2 “

Pour accéder à ce séminaire :

Institut Néel CNRS, Bâtiment K, Salle Rémy Lemaire  (K223)

Résumé : Quantum magnetic insulators based on 4f  ions suffer strong spin-orbit interactions and crystal field effects, which are often found to be the source of anisotropic exchange interactions leading to exotic magnetism. Here, we consider one such example, YbCuS2, relevant to the spin-1/2 zigzag chain based on Kramers Gamma_6 doublets. On top of the anisotropic Heisenberg terms, the material hosts anisotropic interactions represented by the so-called Gamma-term. We studied the general ground state phase diagram of the model and found three highly competing magnetic phases and the two nonmagnetic quantum disordered phases, which all meet at the quantum Lifshitz multicritical point. The quantum-disordered phases include the nematic singlet dimer phase, which continues from the Majumdar-Ghosh singlet state, but has a particular feature: a coexisting robust spin gap and the gapless nematic excitation, which can explain all the  experimental observations of YbCuS2. 
Some parts of this study led to another interesting theoretical aspect:  we figured out a new method to generate exact solutions for general frustration-free  models based on MPS formalism, which we briefly explain if the time allows. 

H Saito, C Hotta, Phys. Rev. Lett. 132, 166701 (2024)
H Saito, C Hotta, arXiv preprint arXiv:2404.10615. 
H Saito, H Nakai, C Hotta, J. Phys. Soc. Jpn. 93, 034701 (2024).

Les organisatrices :

Elsa Lhotel (elsa.lhotel@neel.cnrs.fr)
Florence Levy-Bertrand (florence.levy-bertrand@neel.cnrs.fr)