نتایج جستجو برای: optical conductivity

تعداد نتایج: 313826  

Journal: :Journal of Physics: Condensed Matter 2014

Journal: :Journal of Physics: Condensed Matter 2013

Journal: :Journal of Magnetism and Magnetic Materials 2002

2016
B. Brière A. Kalinko I. Yamada P. Roy J. B. Brubach R. Sopracase M. Zaghrioui V. Ta Phuoc

Optical measurements were carried out by infrared spectroscopy on AA'3B4O12 A-site ordered quadruple perovskite EuCu3Fe4O12 (microscopic sample) as function of temperature. At 240 K (=TMI), EuCu3Fe4O12 undergoes a very abrupt metal to insulator transition, a paramagnetic to antiferromagnetic transition and an isostructural transformation with an abrupt large volume expansion. Above TMI, optical...

Investigating the longitudinal optical conductivity of graphene systems, which is the mostimportant property for opto-electronic devices, for three-layer graphene systems theoretically and numerically is the main purpose of this study. Each layer can be mono- or bi-layer graphene. Separation between layers has been denoted by d, selected to be about ten nanometers. The carrier densities i...

Journal: :Optics letters 2014
Anshuman Kumar Kin Hung Fung M T Homer Reid Nicholas X Fang

Two-dimensional optical materials, such as graphene, can be characterized by surface conductivity. So far, the transformation optics schemes have focused on three-dimensional properties such as permittivity ϵ and permeability μ. In this Letter, we use a scheme for transforming surface currents to highlight that the surface conductivity transforms in a way different from ϵ and μ. We use this sur...

Journal: :Journal of physics. Condensed matter : an Institute of Physics journal 2013
Junhua Zhang Jörg Schmalian Tianqi Li Jigang Wang

Ultrafast optical pump-probe spectroscopy measurements on monolayer graphene reveal significant optical nonlinearities. We show that strongly photoexcited graphene monolayers with 35 fs pulses quasi-instantaneously build up a broadband, inverted Dirac-fermion population. Optical gain emerges and directly manifests itself via a negative conductivity at the near-infrared region for the first 200 ...

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