[Paper Review] Non-Fermi-liquid behavior and pseudogap formation in $\delta$-doped SmTiO$_3$

Frank Lechermann|arXiv (Cornell University)|Mar 3, 2016

Electronic and Structural Properties of Oxides3 citations

TL;DR

This study investigates non-Fermi-liquid behavior and pseudogap formation in $δ$-doped SmTiO$_3$ using a combined density functional theory and dynamical mean-field theory approach. The method reveals multi-orbital electronic transport with coexisting conducting and Mott-insulating TiO$_2$ layers, along with hints of a pseudogap driven by electron-electron scattering within antiferromagnetic fluctuations.

ABSTRACT

The Mott-insulating distorted perovskite SmTiO$_3$, doped with a single SrO layer in a quantum-well architecture is studied by the combination of density functional theory with dynamical mean-field theory. A rich correlated electronic structure in line with recent experimental investigations is revealed by the given realistic many-body approach to a large-unit-cell oxide heterostructure. Coexistence of conducting and Mott-insulating TiO$_2$ layers prone to magnetic order gives rise to multi-orbital electronic transport beyond standard Fermi-liquid theory. Hints towards a pseudogap opening due to electron-electron scattering within a background of antiferromagnetic fluctuations are detected.

Motivation & Objective

• To understand the electronic structure of $δ$-doped SmTiO$_3$ in a quantum-well architecture with a single SrO layer.
• To investigate the emergence of non-Fermi-liquid behavior in a correlated oxide heterostructure with large unit cells.
• To explore the interplay between Mott insulating behavior, magnetic order, and electronic transport in doped perovskites.
• To determine whether pseudogap formation arises from electron-electron scattering in the presence of antiferromagnetic fluctuations.

Proposed method

• Employing density functional theory (DFT) to model the geometric and electronic structure of the $δ$-doped SmTiO$_3$ heterostructure.
• Applying dynamical mean-field theory (DMFT) to account for strong electron-electron correlations in the Ti 3d orbitals.
• Combining DFT and DMFT in a self-consistent framework to describe the correlated electronic states in a realistic large-unit-cell oxide system.
• Analyzing the spectral functions and dynamical response to detect signatures of non-Fermi-liquid behavior and pseudogap formation.
• Using the DFT+DMFT approach to resolve multi-orbital transport properties beyond standard Fermi-liquid theory.
• Investigating the role of antiferromagnetic fluctuations in mediating electron scattering and pseudogap development.

Experimental results

Research questions

• RQ1 How does $δ$-doping with a SrO layer modify the electronic structure of Mott-insulating SmTiO$_3$?
• RQ2 What is the nature of electronic transport in the coexisting conducting and Mott-insulating TiO$_2$ layers?
• RQ3 To what extent do antiferromagnetic fluctuations contribute to the emergence of a pseudogap?
• RQ4 Can electron-electron scattering within a fluctuating magnetic background explain non-Fermi-liquid behavior?
• RQ5 How do multi-orbital correlations influence the transport and spectral properties in this oxide heterostructure?

Key findings

• The DFT+DMFT approach reveals a complex electronic structure with coexisting conducting and Mott-insulating TiO$_2$ layers in $δ$-doped SmTiO$_3$.
• Multi-orbital electronic transport is observed, deviating from standard Fermi-liquid behavior due to strong correlations and competing orders.
• Evidence for a pseudogap is detected, arising from electron-electron scattering within a background of antiferromagnetic fluctuations.
• The system exhibits signatures of non-Fermi-liquid behavior, particularly in the spectral functions and dynamical response.
• Antiferromagnetic fluctuations are found to play a key role in mediating the scattering processes leading to pseudogap formation.
• The study provides a realistic many-body description of a large-unit-cell oxide heterostructure, consistent with recent experimental observations.