The Hubbard model and its strong-coupling version, the Heisenberg one, have been widely studied on the triangular lattice to capture the essential low-temperature properties of different materials. One example is given by transition metal dichalcogenides, as 1T-TaS$_2$, where a large unit cell with 13 Ta atoms forms weakly coupled layers with an isotropic triangular lattice. By using accurate variational Monte Carlo calculations, we report the phase diagram of the $t-t′$ Hubbard model on the triangular lattice, highlighting the differences between positive and negative values of $t′/t$; this result can be captured only by including the charge fluctuations that are always present for a finite electron-electron repulsion. Two spin-liquid regions are detected: one for $t′/t<0$, which persists down to intermediate values of the electron-electron repulsion, and a narrower one for $t′/t>0$. The spin-liquid phase appears to be gapless, though the variational wave function has a nematic character, in contrast to the Heisenberg limit. We do not find any evidence for nonmagnetic Mott phases in the proximity of the metal-insulator transition, at variance with the predictions (mainly based upon strong-coupling expansions in $t/U$) that suggest the existence of a weak-Mott phase that intrudes between the metal and the magnetically ordered insulator.
Magnetic and spin-liquid phases in the frustrated t-t′ Hubbard model on the triangular lattice / Tocchio, L. F.; Montorsi, A.; Becca, F.. - In: PHYSICAL REVIEW. B. - ISSN 2469-9950. - STAMPA. - 102:11(2020), pp. 115150-1-115150-7.
|Titolo:||Magnetic and spin-liquid phases in the frustrated t-t′ Hubbard model on the triangular lattice|
|Data di pubblicazione:||2020|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1103/PhysRevB.102.115150|
|Appare nelle tipologie:||1.1 Articolo in rivista|