Colloquium : Heavy-electron quantum criticality and single-particle spectroscopy

Abstract

Angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM) have become indispensable tools in the study of correlated quantum materials. Both probe complementary aspects of the single-particle excitation spectrum. Taken together, ARPES and STM have the potential to explore properties of the electronic Green function, a central object of many-body theory. In this article, we explicate this potential with a focus on heavy-electron quantum criticality, especially the role of Kondo destruction. We discuss how to probe the Kondo destruction effect across the quantum critical point using ARPES and STM measurements. We place particular emphasis on the question of how to distinguish between the signatures of the initial onset of hybridization-gap formation, which is the "high-energy" physics to be expected in all heavy-electron systems, and those of Kondo destruction, which characterizes the low-energy physics and, hence, the nature of quantum criticality. We survey recent progress and possible challenges in the experimental investigations, compare the STM and ARPES spectra for several quantum critical heavy-electron compounds, and outline the prospects for further advances. CONTENTS I. Introduction 2 II. Quantum criticality 3 A. High-energy excitations, temperature evolution and mass enhancement 5 B. Isothermal evolution at low temperatures 6 C. Further considerations 6 D. Summary of Section II 6 III. ARPES, STM, and the single-particle Green function 6 A. The one-particle Green function 7 B. ARPES and STM 7 C. Probing quantum criticality in the Kondo lattice 8 D. Summary of Section III 9 IV. Quantum criticality in YbRh 2 Si 2 9 Summary of Section IV 11 V. The Cerium-based 115 family: photoemission vs. tunneling spectroscopy 11 A. CeIrIn 5 11 B. CeCoIn 5 12 C. CeRhIn 5 14 D. Further considerations 15 E. Summary of Section V 16 VI. Progress, challenges and prospects 16 A. High energy Kondo features 16 B. Isothermal evolution at low temperatures 17 C. Outlook 17 VII. Conclusion 19 Acknowledgements 19 References 20

Charge density wave and weak Kondo effect in a Dirac semimetal CeSbTe

“…This indicates that the CDW order indeed reduces the DOS near E F significantly by opening large (anisotropic) energy gaps. The spectroscopic signature of the Kondo effect is the characteristic Kondo resonance peaks near E F in the 4f spectral function [50,51]. To probe the 4f-specific spectral function, we performed both off-resonant and on-resonant ARPES spectra near the Ce M edge (4d→4f), as shown in Figure 5.…”

Multiorbital antiferromagnetic metal induced by intramolecular self-doping

“…The characteristics of orbitals accommodating electrons are the primary determinant of the physical and chemical properties of materials, being of particular significance to strongly interacting electron systems. Materials hosting multiple orbitals that form the bands near the Fermi energy, thanks to their synergistic interplay, harbor a variety of emergent phenomena: multiferroics [1,2], exotic superconductivity with variant pairing symmetries [3] and nematicity [4] in d-orbital systems, heavy electron behavior [5,6] and quantum criticality [7,8] in f -orbital systems, and so on. These diverse emergent phenomena appear in a material-specific manner depending on what kinds of orbitals are incorporated in what spatial and energetic configuration.…”

On non-canonical degrees of freedom

“…A unifying theme in the study of strongly correlated materials is the observation of distinct metallic regimes separated by a regime of quantum criticality. Hallmark examples are the cuprates, where a critical 'strange metal' lies between the pseudogap and Fermi liquid metallic regimes [67], and the heavy-fermion compounds where a similarly quantum critical regime is seen to separate conventional Fermi liquid and heavy Fermi liquid regimes [98]. In both cases, a low-temperature transition between the distinct metallic regimes is unambiguously observed in Hall coefficient measurements [99,100].…”