Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of suppressed terahertz absorption in photoexcited graphene   When light is absorbed by a semiconductor, photoexcited charge carriers
enhance the absorption of far-infrared radiation due to intraband transitions.
We observe the opposite behavior in monolayer graphene, a zero-gap
semiconductor with linear dispersion. By using time domain terahertz (THz)
spectroscopy in conjunction with optical pump excitation, we observe a reduced
absorption of THz radiation in photoexcited graphene. The measured spectral
shape of the differential optical conductivity exhibits non-Drude behavior. We
discuss several possible mechanisms that contribute to the observed
low-frequency non-equilibrium optical response of graphene.

34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
6
The categories of this paper are: astro-ph
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex