Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Infrared phonon dynamics of multiferroic BiFeO3 single crystal   We discuss the first infrared reflectivity measurement on a BiFeO3 single
crystal between 5 K and room temperature. The 9 predicted ab-plane E phonon
modes are fully and unambiguously determined. The frequencies of the 4 A1
c-axis phonons are found. These results settle issues between theory and data
on ceramics. Our findings show that the softening of the lowest frequency E
mode is responsible for the temperature dependence of the dielectric constant,
indicating that the ferroelectric transition in BiFeO3 is soft-mode driven.

9
The categories of this paper are: nlin
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con