Lifshitz transition from valence fluctuations in YbAl3

Shouvik Chatterjee,Darrell G Schlom,Haofei I Wei,Kyle M Shen,Kenneth D Finkelstein,Jacob P Ruf

doi:10.1038/s41467-017-00946-1

Shouvik Chatterjee, Darrell G Schlom + Show 4 more

Open Access

https://doi.org/10.1038/s41467-017-00946-1

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Abstract

In mixed-valent Kondo lattice systems, such as YbAl3, interactions between localized and delocalized electrons can lead to fluctuations between two different valence configurations with changing temperature or pressure. The impact of this change on the momentum-space electronic structure is essential for understanding their emergent properties, but has remained enigmatic. Here, by employing a combination of molecular beam epitaxy and in situ angle-resolved photoemission spectroscopy we show that valence fluctuations can lead to dramatic changes in the Fermi surface topology, even resulting in a Lifshitz transition. As the temperature is lowered, a small electron pocket in YbAl3 becomes completely unoccupied while the low-energy ytterbium (Yb) 4f states become increasingly itinerant, acquiring additional spectral weight, longer lifetimes, and well-defined dispersions. Our work presents a unified picture of how local valence fluctuations connect to momentum-space concepts such as band filling and Fermi surface topology in mixed valence systems.

Highlights

In mixed-valent Kondo lattice systems, such as YbAl3, interactions between localized and delocalized electrons can lead to fluctuations between two different valence configurations with changing temperature or pressure
Kondo lattice systems host a wide variety of quantum states such as antiferromagnetism[1], heavy Fermi liquids[2], hidden order[3], and unconventional superconductivity[4], which can often be controlled by modest perturbations using magnetic field or pressure, thereby providing access to quantum phase transitions[5,6,7]
In mixed valence systems[8,9,10], this coupling results in a change of the rare-earth valence, which can be determined by core-level spectroscopies that probe the local chemical environment (r-space)[11,12,13], but the implications for the momentum-space (k-space) electronic structure remain poorly understood

Summary

Introduction

In mixed-valent Kondo lattice systems, such as YbAl3, interactions between localized and delocalized electrons can lead to fluctuations between two different valence configurations with changing temperature or pressure. The local Yb valence decreases as the temperature is lowered, accompanied by a large shift in the chemical potential which leads to a Lifshitz transition of a small electron pocket at Γ, along with the emergence of renormalized heavy quasiparticles near the Fermi energy (EF).

Results

Conclusion