Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Microwave spectroscopy on heavy-fermion systems: probing the dynamics of
  charges and magnetic moments   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.

16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th