# Multiorbital Two-Band Landau–Fermi Liquidness of 1T‑Ti(Se,Te)2 van der Waals Crystals

## TL;DR

This paper studies how electron interactions in 1T-Ti(Se,Te)2 crystals lead to a special metal state that supports superconductivity.

## Contribution

The study introduces a multiorbital two-band model to explain the emergence of a correlated Landau–Fermi liquid state in Ti-based dichalcogenides.

## Key findings

- DFT + DMFT calculations reveal an LFL metal stabilized by Ti-3d correlations.
- Chalcogen p-states remain rigid, leading to anisotropic renormalization of Ti-3d states.
- Orbital-selective reconstruction explains distinct transport responses in Se and Te compounds.

## Abstract

Normal-state Landau–Fermi-liquid (LFL) behavior
is widely
regarded as a prerequisite for low-temperature superconductivity in
1T-TiX
2 (X = Se, Te) van der Waals (vdW) crystals. Clarifying this role requires
a microscopic description of how local electron correlations and Ti–chalcogen
covalence cooperate to shape the low-energy electronic structure in
the noncharge-density-wave (non-CDW) regime. In the present work,
we employ density functional theory combined with dynamical mean-field
theory (DFT + DMFT) to investigate an extended multiorbital (MO) two-band
Hubbard model specifically constructed for these transition-metal
dichalcogenides. The calculations reveal an emergent LFL metal stabilized
by dynamical intra- and interorbital correlations in the Ti-based
manifold, while the chalcogen 4p/5p states remain comparatively rigid
against changes in interaction strength. This orbital-selective reconstruction
leads to a strongly anisotropic renormalization of the Ti-3d sector,
which we identify as a key ingredient for the superconducting phase
diagram of 1T-TiX
2. Beyond
demonstrating the capability of DFT + DMFT to capture such MO correlation
effects, our results show that proximity to a correlated LFL state
naturally accounts for the distinct low-temperature transport responses
of the Se and Te compounds, where modest variations in interaction-to-bandwidth
ratio and orbital occupancy drive markedly different sensitivities
to external tuning parameters such as pressure, doping, or gating.