Spin-liquid versus spiral-order phases in the anisotropic triangular lattice

Abstract

We study the competition between magnetic and spin-liquid phases in the Hubbard model on the anisotropic triangular lattice, which is described by two hopping parameters t and t ′ in different spatial directions and is relevant for layered organic charge-transfer salts. By using a variational approach that includes spiral magnetic order, we provide solid evidence that a spin-liquid phase is stabilized in the strongly-correlated regime and close to the isotropic limit t ′ /t = 1. Otherwise, a magnetically ordered spiral state is found, connecting the (collinear) Néel and the (coplanar) 120• phases. The pitch vector of the spiral phase obtained from the unrestricted Hartree-Fock approximation is substantially renormalized in presence of electronic correlations, and the Néel phase is stabilized in a wide regime of the phase diagram, i.e., for t ′ /t < 0.75. We discuss these results in the context of organic charge-transfer salts.

Staggered Flux State in Two-Dimensional Hubbard Models

“…E is symmetric with respect to t ′ /t = 0 owing to the electron-hole symmetry. 35 Similarly to the case on the frustrated square lattice, E(FS) and E(d−SC) (if the band renormalization is considered 115,116 ) are constant. For the ground state, we find from Fig.…”

Spin-liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

“…It is well known that the perfect nesting of the square lattice means that is insulating for arbitrarily small U/t. For t = t, it is found, numerically, that the Mott transition occurs at around U/t = 10-15, depending on the method used [3,[15][16][17][18][19][20][21]79]. The metal-insulator transition line in Fig.…”

“…This model contains three parameters: U the effective on-site Coulomb repulsion, t the nearest-neighbor hopping integral, and t the next-nearest-neighbor hopping integral along one diagonal only. The Hubbard model on the anisotropic triangular lattice has been studied via a number of approaches [15][16][17][18][19][20][21]. Some methods have suggested that a spin liquid is realized in the insulating phase.…”

Importance of anisotropy in the spin-liquid candidate Me3EtSb[Pd(dmit)2]2

“…If we average the two larger t's of Sb-1, assuming t = (t a + t b )/2 and t = t c , we find that the equivalent t − t model has t /t = 0.77. This model has been previously studied with variational Monte Carlo, 15 where for this value of t /t the critical U for the spinliquid transition is located at U/t ∼ 22, while for the FATL this value is strongly reduced to U/t a ∼ 11. On the other hand, the metal-insulator transition is only slightly affected, raising from U c /t ∼ 6 for the t − t model to U c /t a ∼ 6.75 for the FATL.…”

“…In this way, we are able to treat spiral order and paramagnetic states at the same level of theory and therefore have a sensible comparison of their energies versus U . 15 …”