# Anomalous lattice contraction and emergent electronic phases in Bi-doped Eu$_2$Ir$_2$O$_7$

## TL;DR

This study investigates how bismuth doping in Eu$_2$Ir$_2$O$_7$ affects its lattice structure and electronic phases, revealing anomalous lattice contraction, persistent magnetic transitions, and emergent metallic states near the Weyl semimetal phase.

## Contribution

It provides experimental insights into the effects of Bi doping on lattice and electronic properties in Eu$_2$Ir$_2$O$_7$, highlighting the emergence of a novel metallic ground state.

## Key findings

- Anomalous lattice contraction at low Bi doping.
- Robust all-in/all-out magnetic and metal-insulator transitions.
- Emergence of a metallic phase with no magnetic order at the boundary.

## Abstract

We study the pyrochlore series (Eu$_{1-x}$Bi$_x$)$_2$Ir$_2$O$_7$ for $ 0 \leq x \leq 1$. We show that for small $x$, the lattice undergoes an anomalous contraction but the all-in/all-out and metal-to-insulator transitions remain robust, and the resistivity approaches a $1/T$ dependence at low-T, suggesting proximity to the Weyl semimetallic phase, as previously predicted theoretically. At the boundary between Eu$_2$Ir$_2$O$_7$ and Bi$_2$Ir$_2$O$_7$ a qualitatively different ground state emerges, which is characterized by its unusual metallic behavior and absence of magnetic ordering at least down to $0.02$ K.