Physics Letters B 729 (2014) 177–184
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Physics Letters B
www.elsevier.com/locate/physletb
Mimic the optical conductivity in disordered solids
via gauge/gravity duality
Jia-Rui Sun
a,∗
, Shang-Yu Wu
b,c,d
, Hai-Qing Zhang
e
a
Department of Physics and Institute of Modern Physics, East China University of Science and Technology, Shanghai 200237, China
b
Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan
c
National Center for Theoretical Science, Hsinchu, Taiwan
d
Yau Shing Tung Center, National Chiao Tung University, Hsinchu, Taiwan
e
CFIF, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
article info abstract
Article history:
Received 27 October 2013
Received in revised form 11 December 2013
Accepted 6 January 2014
Available online 8 January 2014
Editor: M. Cveti
ˇ
c
We study the optical conductivity in a (2 + 1)-dimensional non-relativistic field theory holographically
dual to a
(3 + 1)-dimensional charged Lifshitz black brane within the Einstein–Maxwell-dilaton theory.
Surprisingly, we find that the optical AC conductivity satisfies the nontrivial (non-)power law scaling
in the high frequency regime rather than approaching to a constant when the dynamical critical
exponent z
> 1, which is qualitatively similar to those in various disordered solids in condensed matter
systems. Besides, this (non-)power law scaling behavior shows some universality, which is robust against
the temperatures. We argue that the peculiar scaling behavior of AC conductivity may stem from the
couplings of the dilaton field with the gauge fields and also the logarithmic behavior near the boundary
in the Lifshitz spacetime.
© 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/3.0/). Funded by SCOAP
3
.
1. Introduction
The AdS/CFT correspondence [1–3] or generally the gauge/grav-
ity duality, has provided us very effective tools to study the prop-
erties of the strongly coupled quantum field theories which live on
the boundary of certain gravitational backgrounds. One of the most
important characteristics of the gauge/gravity duality is that it is a
kind of strong–weak duality. In view of this duality, various impor-
tant phenomena of the strongly coupled field theories can be stud-
ied by performing calculations on their dual weakly coupled grav-
ity side. Recently, motivated from the study in condensed matter
physics, many attempts have been made in constructing bulk grav-
itational solutions to model numerous types of strongly coupled
phenomena in condensed matter systems, especially close to the
phase transition or quantum critical points, including the super-
conductor (superfluid) phase transition [4], Fermi and non-Fermi
liquids [5], superconductor–insulator transitions [6], etc., for recent
review, see [7,8]. There are also some quantum phase transition
systems in condensed matter physics which contain the Lifshitz-
fixed points have received much attention. On one hand, these
developments successfully extended the gauge/gravity duality into
*
Corresponding author.
E-mail addresses: jrsun@ecus
t.edu.cn (J.-R. Sun), loganwu@gmail.com (S.-Y. Wu),
hqzhang@cfif.ist.utl.pt (H.-Q. Zhang).
the more general form, namely, non-relativistic version [9–16].
On the other hand, they allow us to study strongly coupled sys-
tems toward realistic laboratory conditions by holographic princi-
ple, which may also be used as a test for the gauge/gravity duality
itself.
This Letter focuses on dealing with Lifshitz field theory in
the
framework of the non-relativistic gauge/gravity duality. Fol-
lowing our previous work [17], we continue studying the holo-
graphic optical conductivity in the quantum field theory which
is dual to the Lifshitz black brane with two independent U
(1)
gauge fields [18]. To compare with the phenomena in condensed
matter physics, we work in a
(3 + 1)-dimensional Lifshitz space-
time, i.e., the dual field theory is
(2 + 1)-dimensional, and we
focus on the case of 1
z 2, where z is the dynamical crit-
ical exponent. When z
= 1, the Lifshtiz black brane will return
to the usual Reissner–Nordström (RN)–AdS black brane, therefore,
the optical conductivity we obtain is similar to those studied in
previous AdS/condensed matter literatures, such as [7].However,
when z
> 1 the optical conductivity, especially its AC part, shows
interesting behavior which is less discussed before as far as we
know. More explicitly, we find that the optical conductivity will
possess a non-trivial scaling with respect to the frequency in large
frequency regime when z
> 1, such as ω
s(z)
, where s(z)>0is
afunctionofz. This feature is very interesting, since in the pre-
vious literatures people argued that the large frequency behavior
of the electric conductivity in
(2 +1)-dimensional field theory will
http://dx.doi.org/10.1016/j.physletb.2014.01.005
0370-2693/
© 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/). Funded by
SCOAP
3
.