Microwave spectroscopy on heavy-fermion systems: probing the dynamics of charges and magnetic moments

Abstract

Investigating solids with light gives direct access to charge dynamics, electronic and magnetic excitations. For heavy fermions, one has to adjust the frequency of the probing light to the small characteristic energy scales, leading to spectroscopy with microwaves. We review general concepts of the frequency-dependent conductivity of heavy fermions, including the slow Drude relaxation and the transition to a superconducting state, which we also demonstrate with experimental data taken on UPd2Al3. We discuss the optical response of a Fermi liquid and how it might be observed in heavy fermions. Microwave studies with focus on quantum criticality in heavy fermions concern the charge response, but also the magnetic moments can be addressed via electron spin resonance (ESR). We discuss the case of YbRh2Si2, the open questions concerning ESR of heavy fermions, and how these might be addressed in the future. This includes an overview of the presently available experimental techniques for microwave studies on heavy fermions, with a focus on broadband studies using the Corbino approach and on planar superconducting resonators.

11 pages, 6 figures, proceedings of QCnP 2012

References in corpus (15)

• Fermi-liquid instabilities at magnetic quantum phase transitions
• Quantum Criticality in Heavy Fermion Metals
• Electrodynamics of Correlated Electron Materials
• Imaging the Fano Lattice to 'Hidden Order' Transition in URu2Si2
• Visualizing heavy fermions emerging in a quantum critical Kondo lattice
• Microwave response of vortices in superconducting thin films of Re and Al
• Fermi-surface collapse and dynamical scaling near a quantum critical point
• Probing dynamics of an electron-spin ensemble via a superconducting resonator
• Cyclotron Resonance in the Hidden-Order Phase of URu2Si2
• Quasi-Particle Dynamics in Superconducting Aluminum
• Signature of quantum criticality in photoemission spectroscopy at elevated temperature
• Evolution of the Kondo state of YbRh2Si2 probed by high field ESR
• Dynamic fluctuations in the superconductivity of NbN films from microwave conductivity measurements
• Microwave conductivity of heavy fermions in UPd2Al3
• Microwave inductance of thin metal strips

Cited by in corpus (9)

• Observing electron spin resonance between 0.1 and 67 GHz at temperatures between 50 mK and 300 K using broadband metallic coplanar waveguides
• Superconducting Energy Scales and Anomalous Dissipative Conductivity in Thin Films of Molybdenum Nitride
• Metallic coplanar resonators optimized for low-temperature measurements
• Improving superconducting resonators in magnetic fields by reduced field-focussing and engineered flux screening
• Terahertz Conductivity of the Heavy-Fermion State in CeCoIn5
• Cryogenic frequency-domain electron spin resonance spectrometer based on coplanar waveguides and field modulation
• Optimization of Coplanar Waveguide Resonators for ESR Studies on Metals
• Niobium stripline resonators for microwave studies on superconductors
• Angle-dependent electron spin resonance of YbRh${}_2$Si${}_2$ measured with planar microwave resonators and in-situ rotation