scholarly journals Controlling valley polarisation in graphene via tailored light pulses

2021 ◽  
Author(s):  
M S Mrudul ◽  
Gopal Dixit
Keyword(s):  
Laser Pulses ◽  
Monolayer Graphene ◽  
Cycle Phase ◽  
Two Dimensional ◽  
Additional Degree ◽  
Light Pulses ◽  
Logical Operations ◽  
Two Dimensional Materials ◽  
Hexagonal Materials ◽  
Laser Setup

Abstract Analogous to charge and spin, electrons in solids endows an additional degree of freedom: the valley pseudospin. Two-dimensional hexagonal materials such as graphene exhibit two valleys, labelled as $\mathbf{K}$ and $\mathbf{K}^{\prime}$. These two valleys have the potential to realise logical operations in two-dimensional materials. Obtaining the desired control over valley polarisation between the two valleys is a prerequisite for the logical operations. Recently, it was shown that two counter-rotating circularly polarised laser pulses can induce a significant valley polarisation in graphene. The main focus of the present work is to optimise the valley polarisation in monolayer graphene by controlling different laser parameters, such as wavelength, intensity ratio, frequency ratio and sub-cycle phase in two counter-rotating circularly polarised laser setup. Moreover, an alternate approach, based on single or few-cycle linearly polarised laser pulse, is also explored to induce significant valley polarisation in graphene. Our work could help experimentalists to choose a suitable method with optimised parameter space to obtain the desired control over valley polarisation in monolayer graphene.

scholarly journals Energy loss by fast-travelling charged particles traversing two-dimensional materials

2020 ◽  
Vol 233 ◽  
pp. 03005
Author(s):  
Jaime E. Santos ◽  
Mikhail Vasilevskiy ◽  
Nuno M.R. Peres ◽  
Antti-Pekka Jauho
Keyword(s):  
Thin Films ◽  
Energy Loss ◽  
2D Materials ◽  
Charged Particles ◽  
Monolayer Graphene ◽  
Two Dimensional ◽  
Particle Detection ◽  
Hydrodynamic Approximation ◽  
Radiation Losses ◽  
Two Dimensional Materials

We consider the problem of the radiation losses by fast-traveling particles traversing two-dimensional (2d) materials or thin films. After review¬ing the screening of electromagnetic fields by two dimensional conducting ma¬terials, we obtain the energy loss by a fast particle traversing such a material or film. In particular, we discuss the pattern of radiation emitted by monolayer graphene treated within a hydrodynamic approximation. These results are com¬pared with recent published results using similar approximations and, having in mind a potential application to particle detection, we briefly discuss how one can improve on the signals obtained by using other two-dimensional materials.

scholarly journals Monolayer Graphene Can Emit SHG Waves

2017 ◽  
Vol 3 (1) ◽  
Author(s):  
David N. Carvalho ◽  
Fabio Biancalana ◽  
Andrea Marini
Keyword(s):  
Dirac Equation ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Normal Incidence ◽  
Monolayer Graphene ◽  
Harmonic Waves ◽  
Two Dimensional ◽  
Wide Range ◽  
Two Dimensional Materials ◽  
Breaking Mechanism

AbstractThe usually-held notion that monolayer graphene, a centrosymmetric system, does not allow even-harmonic generation when illuminated at normal incidence is challenged by the discovery of a peculiar effect we term the dynamical centrosymmetry breaking mechanism. This effect results in a global pulse-induced oscillation of the Dirac cones which in turn produces second harmonic waves. We prove that this result can only be found by using the full Dirac equation and show that the widely used semiconductor Bloch equations fail to reproduce this and some other important physics of graphene. These results clear the way for further investigation concerning nonlinear light-matter interactions in a wide range of two-dimensional materials admitting either a gapped or ungapped Dirac-like spectrum.

scholarly journals Accumulation and Control of Spin Waves in Magnonic Dielectric Microresonators by a Comb of Ultrashort Laser Pulses

2021 ◽  
Author(s):  
A. E. Khramova ◽  
M. Kobecki ◽  
I. A. Akimov ◽  
I. V. Savochkin ◽  
M. A. Kozhaev ◽  
...  
Keyword(s):  
Spin Wave ◽  
Repetition Rate ◽  
Spin Waves ◽  
Small Variation ◽  
Laser Pulses ◽  
High Repetition Rate ◽  
Ultrashort Laser Pulses ◽  
Additional Degree ◽  
Light Pulses ◽  
Iron Garnet

Abstract Spin waves in magnetic microresonators are at the core of modern magnonics. Here we demonstrate a new method of tunable excitation of different spin wave modes in magnetic microdisks by using a train of laser pulses coming at a repetition rate higher than the decay rate of spin precession. The microdisks are etched in a transparent bismuth iron garnet film and the light pulses influence the spins nonthermally through the inverse Faraday effect. The high repetition rate of the laser stimulus of 10 GHz establishes an interplay between the spin wave resonances in the frequency and momentum domains. As a result, the excitation efficiency of different spin modes can be tuned by a small variation of the external magnetic field. An additional degree of freedom is provided by scanning the laser spot within the microdisk area. This makes the proposed method for spin wave excitation advantageous for the forthcoming application of magnonics for telecommunication and quantum technologies.

scholarly journals Experimentally derived axial stress–strain relations for two-dimensional materials such as monolayer graphene

Carbon ◽  
2015 ◽  
Vol 81 ◽  
pp. 322-328 ◽  
Author(s):  
Ch. Androulidakis ◽  
G. Tsoukleri ◽  
N. Koutroumanis ◽  
G. Gkikas ◽  
P. Pappas ◽  
...  
Keyword(s):  
Axial Stress ◽  
Monolayer Graphene ◽  
Two Dimensional ◽  
Stress Strain ◽  
Two Dimensional Materials

scholarly journals Ultrahigh thermal isolation across heterogeneously layered two-dimensional materials

2019 ◽  
Vol 5 (8) ◽  
pp. eaax1325 ◽  
Author(s):  
Sam Vaziri ◽  
Eilam Yalon ◽  
Miguel Muñoz Rojo ◽  
Saurabh V. Suryavanshi ◽  
Huairuo Zhang ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Room Temperature ◽  
2D Materials ◽  
Mass Density ◽  
Monolayer Graphene ◽  
Heterogeneous Integration ◽  
Two Dimensional ◽  
Thermal Isolation ◽  
Two Dimensional Materials ◽  
Heat Carriers

Heterogeneous integration of nanomaterials has enabled advanced electronics and photonics applications. However, similar progress has been challenging for thermal applications, in part due to shorter wavelengths of heat carriers (phonons) compared to electrons and photons. Here, we demonstrate unusually high thermal isolation across ultrathin heterostructures, achieved by layering atomically thin two-dimensional (2D) materials. We realize artificial stacks of monolayer graphene, MoS2, and WSe2 with thermal resistance greater than 100 times thicker SiO2 and effective thermal conductivity lower than air at room temperature. Using Raman thermometry, we simultaneously identify the thermal resistance between any 2D monolayers in the stack. Ultrahigh thermal isolation is achieved through the mismatch in mass density and phonon density of states between the 2D layers. These thermal metamaterials are an example in the emerging field of phononics and could find applications where ultrathin thermal insulation is desired, in thermal energy harvesting, or for routing heat in ultracompact geometries.

scholarly journals Ab Initio Simulation of Attosecond Transient Absorption Spectroscopy in Two-Dimensional Materials

2018 ◽  
Vol 8 (10) ◽  
pp. 1777 ◽  
Author(s):  
Shunsuke Sato ◽  
Hannes Hübener ◽  
Umberto De Giovannini ◽  
Angel Rubio
Keyword(s):  
Absorption Spectroscopy ◽  
Density Functional ◽  
Transient Absorption ◽  
Hexagonal Boron Nitride ◽  
Laser Pulses ◽  
Transient Absorption Spectroscopy ◽  
Band Model ◽  
Two Dimensional ◽  
Energy Bands ◽  
Two Dimensional Materials

We extend the first-principles analysis of attosecond transient absorption spectroscopy to two-dimensional materials. As an example of two-dimensional materials, we apply the analysis to monolayer hexagonal boron nitride (h-BN) and compute its transient optical properties under intense few-cycle infrared laser pulses. Nonadiabatic features are observed in the computed transient absorption spectra. To elucidate the microscopic origin of these features, we analyze the electronic structure of h-BN with density functional theory and investigate the dynamics of specific energy bands with a simple two-band model. Finally, we find that laser-induced intraband transitions play a significant role in the transient absorption even for the two-dimensional material and that the nonadiabatic features are induced by the dynamical Franz–Keldysh effect with an anomalous band dispersion.

Redox-Active Approach Towards New Magnetic And Conductive Two-Dimensional Materials

2018 ◽  
Author(s):  
Penny Perlepe ◽  
Rodolphe Clérac ◽  
Itziar Oyarzabal ◽  
Corine Mathonière
Keyword(s):  
Two Dimensional ◽  
Active Approach ◽  
Redox Active ◽  
Two Dimensional Materials

scholarly journals Polarization-sensitive photodetectors based on three-dimensional molybdenum disulfide (MoS2) field-effect transistors

Nanophotonics ◽  
2020 ◽  
Vol 9 (16) ◽  
pp. 4719-4728
Author(s):  
Tao Deng ◽  
Shasha Li ◽  
Yuning Li ◽  
Yang Zhang ◽  
Jingye Sun ◽  
...  
Keyword(s):  
Molybdenum Disulfide ◽  
Field Effect ◽  
High Performance ◽  
Field Effect Transistors ◽  
Three Dimensional ◽  
Polarized Light ◽  
Optical Field ◽  
Two Dimensional ◽  
Polarization Ratio ◽  
Two Dimensional Materials

AbstractThe molybdenum disulfide (MoS2)-based photodetectors are facing two challenges: the insensitivity to polarized light and the low photoresponsivity. Herein, three-dimensional (3D) field-effect transistors (FETs) based on monolayer MoS2 were fabricated by applying a self–rolled-up technique. The unique microtubular structure makes 3D MoS2 FETs become polarization sensitive. Moreover, the microtubular structure not only offers a natural resonant microcavity to enhance the optical field inside but also increases the light-MoS2 interaction area, resulting in a higher photoresponsivity. Photoresponsivities as high as 23.8 and 2.9 A/W at 395 and 660 nm, respectively, and a comparable polarization ratio of 1.64 were obtained. The fabrication technique of the 3D MoS2 FET could be transferred to other two-dimensional materials, which is very promising for high-performance polarization-sensitive optical and optoelectronic applications.

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