Charge fluctuations in the unconventional metallic state ofLi0.9Mo6O17

Abstract

Charge fluctuations in the quasi-one-dimensional material Li 0.9 Mo 6 O 17 are analyzed based on a multiorbital extended Hubbard model. A charge-ordering transition induced by Coulomb repulsion is found with a particular charge-ordering pattern. The metallic phase is characterized by the presence of a charge collective mode which softens signaling the proximity to the charge order transition. We argue that the scattering between electrons mediated by these charge fluctuations can lead to non-Fermi liquid behavior in a quasi-one-dimensional system consistent with the unconventional metallic behavior observed above the superconducting transition in Li 0.9 Mo 6 O 17 .

Multi-orbital physics in lithium-molybdenum purple-bronze: going beyond paradigm

“…3b) therein and later the tendency was confirmed in a numerical DFT+DMFT study in reference [22]. This corresponds to an enhanced charge susceptibility and indeed a direct calculation [36] within a simpler RPA framework showed explicitly such enhancement with a broad peak around q = (0, π/(b/2), π/(c/2)). Staying on the RPA ground, this implies an enhancement of an inverse dielectric constant …”

“…Then from result of reference [36], by taking a Fourier transform of −1 (q), we find that a pair of fermions located at a characteristic distance |r ex | = (b/2) 2 + (c/2) 2 can interact quite strongly. This statement is valid no matter if the system actually reaches the charge ordering [36] or only stays in the vicinity of it. We can then postulate an existence of a small exciton of a size r ex , where electron and hole are bound on a single plaquette consisting out of four Mo sites.…”

Triplet superconductivity in a model ofLi0.9Mo6O17

“…In the last years there has been a very important theoretical effort [24][25][26][27] to reduce the complexity of the unit cell to microscopic Hamiltonians reproducing different aspects of this phenomenology. In this article, we present a microscopic theory for the unconventional superconducting properties observed in Li 0.9 Mo 6 O 17 .…”

“…A Slater-Koster tight binding parametrization of the system has been propoposed in Ref. 24 and the role of long-range Coulomb couplings in the anomalies of the metallic phase has been also studied 27 . Here, we consider a strongly correlated model, which can capture the essential physics of Li 0.9 Mo 6 O 17 24 consisting on an extended Hubbard lattice with 4 Mo-atoms per unit cell, which reads:…”

“…where H 0 is the non-interacting tight-binding Hamiltonian. The one-electron Hamiltonian can be expressed in terms of Bloch waves with the following non-zero matrix elements, the intra-ladder: 24,27,31 . The Fermi surface, close to one quarter-filling, n = 0.225, is shown in Fig.…”