Coexisting Kondo hybridization and itinerant f-electron ferromagnetism in UGe2

Abstract

Kondo hybridization in partially filled f-electron systems conveys significant amount of electronic states sharply near the Fermi energy leading to various instabilities from superconductivity to exotic electronic orders. UGe2 is a 5f heavy fermion system, where the Kondo hybridization is interrupted by the formation of two ferromagnetic phases below a 2nd order transition Tc ~ 52 K and a crossover transition Tx ~ 32 K. These two ferromagnetic phases are concomitantly related to a spin-triplet superconductivity that only emerges and persists inside the magnetically ordered phase at high pressure. The origin of the two ferromagnetic phases and how they form within a Kondo-lattice remain ambiguous. Using scanning tunneling microscopy and spectroscopy, we probe the spatial electronic states in the UGe2 as a function of temperature. We find a Kondo resonance and sharp 5f-electron states near the chemical potential that form at high temperatures above Tc in accordance with our density functional theory (DFT) + Gutzwiller calculations. As temperature is lowered below Tc, the resonance narrows and eventually splits below Tx dumping itinerant f-electron spectral weight right at the Fermi energy. Our findings suggest a Stoner mechanism forming the highly polarized ferromagnetic phase below Tx that itself sets the stage for the emergence of unconventional superconductivity at high pressure.

arXiv comment14 pages, 4 figures, In press- Physical Review Research (Vol. 4, No. 2) https://link.aps.org/doi/10.1103/PhysRevResearch.4.L022030

References in corpus (31)

• Search for Majorana fermions in superconductors
• Fermi-liquid instabilities at magnetic quantum phase transitions
• Topological superconductors: a review
• Superconducting phases of f-electron compounds
• Onset of antiferromagnetism in heavy fermion metals
• How do Fermi liquids get heavy and die?
• Superconductivity on the border of weak itinerant ferromagnetism in UCoGe
• Microscopic evidence for a chiral superconducting order parameter in the heavy fermion superconductor UTe2
• Imaging the Fano Lattice to 'Hidden Order' Transition in URu2Si2
• Visualizing heavy fermions emerging in a quantum critical Kondo lattice
• Imaging Cooper Pairing of Heavy Fermions in CeCoIn5
• Scaling of magnetic fluctuations near a quantum phase transition
• Pressure dependence of the magnetization in the ferromagnetic superconductor UGe_2
• Visualizing the Formation of the Kondo Lattice and the Hidden Order in URu2Si2
• Quantum Criticality and Global Phase Diagram of Magnetic Heavy Fermions
• Electron Cotunneling into a Kondo Lattice
• Ferromagnetic superconductivity driven by changing Fermi surface topology
• Differential Conductance and Quantum Interference in Kondo Systems
• Superconductivity and Ferromagnetic Quantum Criticality in Uranium Compounds
• Slave Boson Theory of Orbital Differentiation with Crystal Field Effects: Application to UO${}_2$
• Magnetic Properties of a Pressure-induced Superconductor UGe${}_2$
• Tunneling into clean Heavy Fermion Compounds: Origin of the Fano Lineshape
• Antiferromagnetism and Superconductivity in Cerium based Heavy Fermion Compounds
• Quasiparticle interference in heavy Fermion superconductor CeCoIn_5
• Orbital-selective Kondo entanglement and antiferromagnetic order in USb${}_2$
• Orbital-selective Kondo-lattice and enigmatic f-electrons emerging from inside the antiferromagnetic phase of a heavy fermion
• Stoner gap in the superconducting ferromagnet UGe2
• Thermoelectric power quantum oscillations in the ferromagnet UGe${}_2$
• Ultra-High Resolution Neutron Spectroscopy of Low-Energy Spin Dynamics in UGe${}_2$
• Electronic structure of UGe${}_2$ at ambient pressure: comparison with X-ray photoemission spectra
• Optical spectra of the heavy fermion uniaxial ferromagnet UGe${}_2$