Fermi-surface evolution in Yb-substituted CeCoIn5

A Polyakov,Z Fisk,J Wosnitza,D Hurt,B Bergk,C Capan,M Côté,B Prévost,I Sheikin,S Blackburn,O Ignatchik,K Götze,G Seyfarth,Manuel Richter,A D Bianchi,R G Goodrich

doi:10.1103/physrevb.85.245119

Abstract

We report results of systematic de Haas--van Alphen (dHvA) studies on Ce${}_{1\ensuremath{-}x}$Yb${}_{x}$CoIn${}_{5}$ single crystals with varying Yb concentration. For $x=0.1$, the well-known Fermi surfaces and the heavy effective masses of CeCoIn${}_{5}$ ($x=0$) have changed only slightly. We start to observe changes of the Fermi-surface topology at $x=0.2$ leading to a drastic reconstruction above $x=0.55$. At these concentrations, the effective masses are reduced considerably to values between 0.7 and 2.6 free electron masses. For both YbCoIn${}_{5}$ and CeCoIn${}_{5}$, the angular-resolved dHvA frequencies can be very well described by conventional density-functional theory calculations. Projection of the Bloch states onto atomic Yb-$4f$ orbitals yields a $4f$ occupation of $13.7$ electrons, in agreement with previous experimental results indicating an intermediate Yb valence of $+2.3$.

Highlights

The interplay of partially filled 4f or 5f orbitals with conduction-band electrons is a key ingredient for the emergence of heavy-fermion behavior
The resulting Kondo resonances modify the electronic-excitation spectrum and the Fermi surface concomitant with heavy effective band-structure masses.1. These correlated electrons may further lead to nonFermi-liquid behavior and unconventional superconductivity often in conjunction with a quantum critical point (QCP), i.e., a zero-temperature phase transition tuned by some external control parameter such as pressure, magnetic field, or composition
A likely candidate might be the band that gives rise to the complicated multiconnected Fermi surface resulting in the β orbits in CeCoIn5.34 For both of these orbits, β1 and β2, we find effective masses of about 53me at 13 T and 010 = 7◦

Summary

Introduction

The interplay of partially filled 4f or 5f orbitals with conduction-band electrons is a key ingredient for the emergence of heavy-fermion behavior. The resulting Kondo resonances modify the electronic-excitation spectrum and the Fermi surface concomitant with heavy effective band-structure masses.. The resulting Kondo resonances modify the electronic-excitation spectrum and the Fermi surface concomitant with heavy effective band-structure masses.1 These correlated electrons may further lead to nonFermi-liquid behavior and unconventional superconductivity often in conjunction with a quantum critical point (QCP), i.e., a zero-temperature phase transition tuned by some external control parameter such as pressure, magnetic field, or composition.. There exists a further magnetic-field-driven antiferromagnetic QCP near the upper critical field.6–9 It has been speculated, that at an antiferromagnetic QCP the Fermi surface changes when the system crosses over from a normal antiferromagnetic metal to a strongly correlated Fermi liquid.. There are indications that CeCoIn5 is close to an antiferromagnetic QCP, situated just on the low-pressure side, i.e., negative pressure would be needed to reach it. As a unique feature, there exists a further magnetic-field-driven antiferromagnetic QCP near the upper critical field. It has been speculated, that at an antiferromagnetic QCP the Fermi surface changes when the system crosses over from a normal antiferromagnetic metal to a strongly correlated Fermi liquid. This makes our study of the influence of Yb doping on the Fermi surface in CeCoIn5 of particular interest

Methods

Results

Conclusion