A Striped Electron Fluid on (111) KTaO$_3$
P. Villar Arribi, A. Paramekanti, Michael R. Norman

TL;DR
This paper models the electron behavior at the EuO/(111) KTaO$_3$ interface, revealing a magnetic stripe instability that explains observed transport anisotropy and suggesting a link to superconductivity.
Contribution
It introduces a minimal tight binding and $k ext{ extperiodcentered}p$ model capturing the magnetic stripe order and its effects on the 2DEG in EuO/KTaO$_3$.
Findings
Hexagonal Fermi surface with enhanced 2$k_F$ susceptibility.
Magnetic stripe instability leads to partial Fermi surface gapping.
Possible connection between stripe order and superconductivity.
Abstract
A recent study has revealed that the low carrier density electron gas (2DEG) induced at the interface of EuO and (111) KTaO exhibits a broken symmetry phase with a strong in-plane anisotropy of the resistivity. We present a minimal tight binding model of this (111) 2DEG, including the large spin-orbit coupling from the Ta ions, which reveals a hexagonal Fermi surface with a highly enhanced 2 electronic susceptibility. We argue that repulsive electronic interactions, together with a ferromagnetic EuO substrate, favor a magnetic stripe instability leading to a partially gapped Fermi surface. Such a stripe state, or its vestigial nematicity, could explain the observed transport anisotropy. We propose a theory for the low energy states, which captures the key results from our tight-binding study, and further reveals the intertwined dipolar and octupolar…
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