scholarly journals Calculation of the Infrared Intensity of Crystalline Systems. A Comparison of Three Strategies Based on Berry Phase, Wannier Function, and Coupled-Perturbed Kohn–Sham Methods

2018 ◽  
Vol 123 (13) ◽  
pp. 8336-8346 ◽  
Author(s):  
R. Dovesi ◽  
B. Kirtman ◽  
L. Maschio ◽  
J. Maul ◽  
F. Pascale ◽  
...  
Keyword(s):  
Berry Phase ◽  
Wannier Function ◽  
Infrared Intensity

scholarly journals Interface-induced sign reversal of the anomalous Hall effect in magnetic topological insulator heterostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Fei Wang ◽  
Xuepeng Wang ◽  
Yi-Fan Zhao ◽  
Di Xiao ◽  
Ling-Jie Zhou ◽  
...  
Keyword(s):  
Hall Effect ◽  
Electric Fields ◽  
First Principles ◽  
Berry Phase ◽  
Condensed Matter ◽  
Anomalous Hall Effect ◽  
First Principles Calculations ◽  
Sign Reversal ◽  
Berry Curvature ◽  
Topological Materials

AbstractThe Berry phase picture provides important insights into the electronic properties of condensed matter systems. The intrinsic anomalous Hall (AH) effect can be understood as the consequence of non-zero Berry curvature in momentum space. Here, we fabricate TI/magnetic TI heterostructures and find that the sign of the AH effect in the magnetic TI layer can be changed from being positive to negative with increasing the thickness of the top TI layer. Our first-principles calculations show that the built-in electric fields at the TI/magnetic TI interface influence the band structure of the magnetic TI layer, and thus lead to a reconstruction of the Berry curvature in the heterostructure samples. Based on the interface-induced AH effect with a negative sign in TI/V-doped TI bilayer structures, we create an artificial “topological Hall effect”-like feature in the Hall trace of the V-doped TI/TI/Cr-doped TI sandwich heterostructures. Our study provides a new route to create the Berry curvature change in magnetic topological materials that may lead to potential technological applications.

scholarly journals A hybrid broadband metalens operating at ultraviolet frequencies

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Farhan Ali ◽  
Serap Aksu
Keyword(s):  
Dielectric Material ◽  
Berry Phase ◽  
Uv Light ◽  
Fdtd Method ◽  
Numerical Aperture ◽  
Limited Range ◽  
Unit Cell ◽  
Dielectric Constants ◽  
Phase Method ◽  
Frequency Range

AbstractThe investigation on metalenses have been rapidly developing, aiming to bring compact optical devices with superior properties to the market. Realizing miniature optics at the UV frequency range in particular has been challenging as the available transparent materials have limited range of dielectric constants. In this work we introduce a low absorption loss and low refractive index dielectric material magnesium oxide, MgO, as an ideal candidate for metalenses operating at UV frequencies. We theoretically investigate metalens designs capable of efficient focusing over a broad UV frequency range (200–400 nm). The presented metalenses are composed of sub-wavelength MgO nanoblocks, and characterized according to the geometric Pancharatnam–Berry phase method using FDTD method. The presented broadband metalenses can focus the incident UV light on tight focal spots (182 nm) with high numerical aperture ($$\hbox {NA}\approx 0.8$$ NA ≈ 0.8 ). The polarization conversion efficiency of the metalens unit cell and focusing efficiency of the total metalens are calculated to be as high as 94%, the best value reported in UV range so far. In addition, the metalens unit cell can be hybridized to enable lensing at multiple polarization states. The presented highly efficient MgO metalenses can play a vital role in the development of UV nanophotonic systems and could pave the way towards the world of miniaturization.

scholarly journals Enhancing the Optical Efficiency of Near-Eye Displays with Liquid Crystal Optics

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 107
Author(s):  
Tao Zhan ◽  
En-Lin Hsiang ◽  
Kun Li ◽  
Shin-Tson Wu
Keyword(s):  
Virtual Reality ◽  
Liquid Crystal ◽  
High Efficiency ◽  
Berry Phase ◽  
Optical Element ◽  
Liquid Crystal Polymer ◽  
Proof Of Concept ◽  
Optical Efficiency ◽  
Crystal Polymer ◽  
Light Efficiency

We demonstrate a light efficient virtual reality (VR) near-eye display (NED) design based on a directional display panel and a diffractive deflection film (DDF). The DDF was essentially a high-efficiency Pancharatnam-Berry phase optical element made of liquid crystal polymer. The essence of this design is directing most of the display light into the eyebox. The proposed method is applicable for both catadioptric and dioptric VR lenses. A proof-of-concept experiment was conducted with off-the-shelf optical parts, where the light efficiency was enhanced by more than 2 times.

Rotational Doppler Frequency Shift from Time‐Evolving High‐Order Pancharatnam–Berry Phase: A Metasurface Approach

2021 ◽  
pp. 2000576
Author(s):  
Fuyong Yue ◽  
A. Aadhi ◽  
Riccardo Piccoli ◽  
Vincenzo Aglieri ◽  
Roberto Macaluso ◽  
...  
Keyword(s):  
Frequency Shift ◽  
Berry Phase ◽  
Doppler Frequency ◽  
Doppler Frequency Shift ◽  
High Order

Wave-Vector-Varying Pancharatnam-Berry Phase Photonic Spin Hall Effect

2021 ◽  
Vol 126 (8) ◽  
Author(s):  
Wenguo Zhu ◽  
Huadan Zheng ◽  
Yongchun Zhong ◽  
Jianhui Yu ◽  
Zhe Chen
Keyword(s):  
Hall Effect ◽  
Wave Vector ◽  
Berry Phase ◽  
Spin Hall Effect

scholarly journals Scattering Analysis and Efficiency Optimization of Dielectric Pancharatnam–Berry-Phase Metasurfaces

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 586
Author(s):  
Chen-Yi Yu ◽  
Qiu-Chun Zeng ◽  
Chih-Jen Yu ◽  
Chien-Yuan Han ◽  
Chih-Ming Wang
Keyword(s):  
Phase Modulation ◽  
Rotation Angle ◽  
Berry Phase ◽  
Fine Tuning ◽  
Design Rule ◽  
Polarization Conversion ◽  
Swarm Optimization ◽  
Efficiency Optimization ◽  
Phase Type ◽  
Gradient Phase

In this study, the phase modulation ability of a dielectric Pancharatnam–Berry (PB) phase metasurface, consisting of nanofins, is theoretically analyzed. It is generally considered that the optical thickness of the unit cell of a PB-phase metasurface is λ/2, i.e., a half-waveplate for polarization conversion. It is found that the λ/2 is not essential for achieving a full 2π modulation. Nevertheless, a λ/2 thickness is still needed for a high polarization conversion efficiency. Moreover, a gradient phase metasurface is designed. With the help of the particle swarm optimization (PSO) method, the wavefront errors of the gradient phase metasurface are reduced by fine-tuning the rotation angle of the nanofins. The diffraction efficiency of the gradient phase metasurface is thus improved from 73.4% to 87.3%. This design rule can be utilized to optimize the efficiency of phase-type meta-devices, such as meta-deflectors and metalenses.

scholarly journals Algebraic approach and Berry phase of a Hamiltonian with a general SU(1, 1) symmetry

2021 ◽  
Vol 62 (7) ◽  
pp. 071701
Author(s):  
E. Choreño ◽  
R. Valencia ◽  
D. Ojeda-Guillén
Keyword(s):  
Berry Phase ◽  
Algebraic Approach

scholarly journals Berry-phase gates for fast and robust control of atomic clock states

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Yunheung Song ◽  
Jongseok Lim ◽  
Jaewook Ahn
Keyword(s):  
Robust Control ◽  
Berry Phase ◽  
Atomic Clock

scholarly journals Functional THz emitters based on Pancharatnam-Berry phase nonlinear metasurfaces

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Cormac McDonnell ◽  
Junhong Deng ◽  
Symeon Sideris ◽  
Tal Ellenbogen ◽  
Guixin Li
Keyword(s):  
Amino Acids ◽  
Linear Polarization ◽  
Berry Phase ◽  
Science And Technology ◽  
Optical Control ◽  
Biomedical Science ◽  
Spin States ◽  
Single Cycle ◽  
All Optical ◽  
Thz Waves

AbstractRecent advances in the science and technology of THz waves show promise for a wide variety of important applications in material inspection, imaging, and biomedical science amongst others. However, this promise is impeded by the lack of sufficiently functional THz emitters. Here, we introduce broadband THz emitters based on Pancharatnam-Berry phase nonlinear metasurfaces, which exhibit unique optical functionalities. Using these new emitters, we experimentally demonstrate tunable linear polarization of broadband single cycle THz pulses, the splitting of spin states and THz frequencies in the spatial domain, and the generation of few-cycle pulses with temporal polarization dispersion. Finally, we apply the ability of spin control of THz waves to demonstrate circular dichroism spectroscopy of amino acids. Altogether, we achieve nanoscale and all-optical control over the phase and polarization states of the emitted THz waves.

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