Nesting-driven multipolar order in CeB6 from photoemission tomography.

A Koitzsch,P Y Portnichenko,V B Filipov,V N Strocov,L L Lev,J Ollivier,N Heming,A V Dukhnenko,D S Inosov,N Y Shitsevalova,M Knupfer,B Büchner

doi:10.1038/ncomms10876

Abstract

Some heavy fermion materials show so-called hidden-order phases which are invisible to many characterization techniques and whose microscopic origin remained controversial for decades. Among such hidden-order compounds, CeB6 is of model character due to its simple electronic configuration and crystal structure. Apart from more conventional antiferromagnetism, it shows an elusive phase at low temperatures, which is commonly associated with multipolar order. Here we show that this phase roots in a Fermi surface instability. This conclusion is based on a full 3D tomographic sampling of the electronic structure by angle-resolved photoemission and comparison with inelastic neutron scattering data. The hidden order is mediated by itinerant electrons. Our measurements will serve as a paradigm for the investigation of hidden-order phases in f-electron systems, but also generally for situations where the itinerant electrons drive orbital or spin order.

Highlights

Some heavy fermion materials show so-called hidden-order phases which are invisible to many characterization techniques and whose microscopic origin remained controversial for decades
They are characterized by a rich low-temperature phase diagram and it is assumed that the multipolar moments of the f-electrons in their specific crystal field environment play a decisive role[5,6]
CeB6 is a heavy-fermion material showing a mass enhancement of the order of 100, which is due to the hybridization of the localized f-electrons with the itinerant conduction electrons

Summary

Introduction

Some heavy fermion materials show so-called hidden-order phases which are invisible to many characterization techniques and whose microscopic origin remained controversial for decades Among such hidden-order compounds, CeB6 is of model character due to its simple electronic configuration and crystal structure. The phase diagram is more complex: the antiferromagnetism is preceded by a famous hidden order state at TQ 1⁄4 3.2 K, the so called antiferroquadrupolar phase (AFQ), which has been explained by the ordering of quadrupole moments with QAFQ 1⁄4 (p, p, p)[10,11] The latter has long been elusive to neutron diffraction experiments and was first directly visualized by X-ray scattering[12]. The strength of the magnetic interactions is mediated by the conduction electrons and depends on the low-energy electronic structure It can be expressed within linear response theory by the Lindhard function[16]. This deficiency calls for a detailed investigation of the band structure and the Fermi surface of CeB6

Methods

Results

Conclusion