Distinct nature of orbital-selective Mott phases dominated by low-energy local spin fluctuations

Abstract

Quantum orbital selective Mott (OSM) transitions are investigated within dynamical mean-field theory based on a two-orbital Hubbard model with different bandwidth at half filling. We find two distinct OSM phases both showing coexistence of itinerant electrons and localized spins, dependent on whether the Hund's coupling is full or of Ising type. The critical values and the nature of the OSM transitions are efficiently determined by entanglement entropy. We reveal that vanishing of the Kondo energy scale evidenced by absence of local spin fluctuations at low frequency in local dynamical spin susceptibility is responsible for the appearance of non-Fermi-liquid OSM phase in Ising Hund's coupling case. We argue that this scenario can also be applied to account for emergent quantum non-Fermi liquid in one-band Hubbard model when short-range antiferromagnetic order is considered.PACS numbers: I.arXiv:1808.05786v1 [cond-mat.str-el]

Charge singlets and orbital-selective charge density wave transitions

“…In multi-orbital language, one of the key conceptual interests is the possibility that the distinct values of the ratio of interaction strength to kinetic energy in the different bands might result in separate insulator transitions, i.e. the possibility of an 'orbital-selective' Mott transition (OSMT) [20][21][22][23][24][25][26][27][28][29][30][31].…”

Orbitally selective breakdown of the Fermi liquid and simultaneous enhancement of metallic and insulating states in correlated multiband systems with spin-orbit coupling

“…Now we discuss the underlying physics for the OSnFL state. Since the nature of correlated metals is controlled by the low-energy excitations in the absence of SOC for multi-band systems [52,53], we performed similar calculations for the dynamical susceptibilities χ ii (ω) of total, orbital, and spin angular momentums with i = J, L, and S, respectively, at U = 2.58 and λ = 0.12, as shown in Fig. 5 as…”

“…This result is similar to that obtained with totally six bath sites. It is obvious that the low-energy excitations of the total angular momentum J are mainly contributed by the spin fluctuations and the high-energy ones are ascribed to the excitations of the total orbital angular momentum L. Since the low-energy excitations were found to dominate the physical properties of the correlated multiorbital systems [52,53], we now pay attention on the low-energy spin fluctuations. Fig.…”

“…The low-energy spin fluctuations consist of two parts, one is attributed to the Kondo screening of spins in d yz/xz bands by itinerant electrons, and the other is ascribed to the existence of spin triplets formed by 4 electrons in 3 t 2g orbitals[52,53]. At λ = 0.14, the system becomes a Fermi liquid.…”

Charge Singlets and Orbital Selective Charge Density Wave Transitions

“…In multi-orbital language, one of the key conceptual interests is the possibility that the distinct values of the ratio of interaction strength to kinetic energy in the different bands might result in separate insulator transitions, i.e. the possibility of an 'orbital-selective' Mott transition (OSMT) [19][20][21][22][23][24][25][26].…”