scholarly journals Terahertz emission from GaAs-AlGaAs core-shell nanowires on Si (100) substrate: Effects of applied magnetic field and excitation wavelength

2013 ◽  
Vol 102 (6) ◽  
pp. 063101 ◽  
Author(s):  
Jasher John Ibanes ◽  
Ma. Herminia Balgos ◽  
Rafael Jaculbia ◽  
Arnel Salvador ◽  
Armando Somintac ◽  
...  
2018 ◽  
Vol 9 ◽  
pp. 1512-1526 ◽  
Author(s):  
Tudor D Stanescu ◽  
Anna Sitek ◽  
Andrei Manolescu

We consider core–shell nanowires with prismatic geometry contacted with two or more superconductors in the presence of a magnetic field applied parallel to the wire. In this geometry, the lowest energy states are localized on the outer edges of the shell, which strongly inhibits the orbital effects of the longitudinal magnetic field that are detrimental to Majorana physics. Using a tight-binding model of coupled parallel chains, we calculate the topological phase diagram of the hybrid system in the presence of non-vanishing transverse potentials and finite relative phases between the parent superconductors. We show that having finite relative phases strongly enhances the stability of the induced topological superconductivity over a significant range of chemical potentials and reduces the value of the critical field associated with the topological quantum phase transition.


2021 ◽  
Author(s):  
Jingjie Ge ◽  
Riccardo Ruixi Chen ◽  
Xiao Ren ◽  
Xia Li ◽  
Jiawei Liu ◽  
...  

<p>Rational design of active oxygen evolution reaction (OER) catalysts is critical for the overall efficiency of water electrolysis. OER reactants and products’ differing spin states is one of causes to slow OER kinetics. Thus, spin conservation plays a crucial role in enhancing OER performance. In this work, we design ferromagnetic (FM)–antiferromagnetic (AFM) Fe<sub>3</sub>O<sub>4</sub>@Ni(OH)<sub>2</sub> core–shell catalysts. The interfacial FM–AFM coupling of these catalysts facilitates selective removal of electrons with spin direction opposing the magnetic moment of FM core, improving OER kinetics. The shell thickness is found critical in retaining the coupling effect for OER enhancement. The magnetic domain structure of the FM core also plays a critical role. With a multiple domain core, the applied magnetic field aligns the magnetic domains, optimising the electron transport process. A significant enhancement of OER activity is observed for the multiple domain core catalysts. With a single domain FM core with ordered magnetic dipoles, the spin-selective electron transport with minimal scattering is facilitated even without an applied magnetic field. We therefore draw a magnetism/OER activity model that depends on two main parameters: interfacial spin coupling and domain structure. Our findings provide new design principles for active OER catalysts.</p>


2018 ◽  
Vol 29 (20) ◽  
pp. 205205 ◽  
Author(s):  
Jakub Płachta ◽  
Emma Grodzicka ◽  
Anna Kaleta ◽  
Sławomir Kret ◽  
Lech T Baczewski ◽  
...  

2021 ◽  
Author(s):  
Jingjie Ge ◽  
Riccardo Ruixi Chen ◽  
Xiao Ren ◽  
Xia Li ◽  
Jiawei Liu ◽  
...  

<p>Rational design of active oxygen evolution reaction (OER) catalysts is critical for the overall efficiency of water electrolysis. OER reactants and products’ differing spin states is one of causes to slow OER kinetics. Thus, spin conservation plays a crucial role in enhancing OER performance. In this work, we design ferromagnetic (FM)–antiferromagnetic (AFM) Fe<sub>3</sub>O<sub>4</sub>@Ni(OH)<sub>2</sub> core–shell catalysts. The interfacial FM–AFM coupling of these catalysts facilitates selective removal of electrons with spin direction opposing the magnetic moment of FM core, improving OER kinetics. The shell thickness is found critical in retaining the coupling effect for OER enhancement. The magnetic domain structure of the FM core also plays a critical role. With a multiple domain core, the applied magnetic field aligns the magnetic domains, optimising the electron transport process. A significant enhancement of OER activity is observed for the multiple domain core catalysts. With a single domain FM core with ordered magnetic dipoles, the spin-selective electron transport with minimal scattering is facilitated even without an applied magnetic field. We therefore draw a magnetism/OER activity model that depends on two main parameters: interfacial spin coupling and domain structure. Our findings provide new design principles for active OER catalysts.</p>


2019 ◽  
Vol 33 (13) ◽  
pp. 1950131 ◽  
Author(s):  
Lei Shi ◽  
Zu-Wei Yan

Within the framework of the effective-mass approximation and by using a variational and perturbation approach, the binding energies and photoionization cross-sections of donor and acceptor impurities in an inverted core/shell ellipsoidal spherical quantum dot under an applied magnetic field have been studied. We have calculated the binding energies of both donor and acceptor impurities as a function of the core and shell sizes and shapes with different impurity positions under the applied magnetic field. In addition, the corresponding photoionization cross-section is calculated. Our results show that the binding energy of the acceptor impurity is larger than that of the donor impurity, and both of them with different impurity positions and quantum ellipsoid anisotropies will exhibit a nonmonotonic change. The peak value of the photoionization cross-section will reach a maximum with the increasing ratio R1/R2. It is found that the applied magnetic field can be an effective means of enhancing the photoionization cross-section of an impurity state in such core/shell quantum dot system.


2015 ◽  
Vol 91 (11) ◽  
Author(s):  
Miquel Royo ◽  
Carlos Segarra ◽  
Andrea Bertoni ◽  
Guido Goldoni ◽  
Josep Planelles

2004 ◽  
Vol 853 ◽  
Author(s):  
Zuqin Liu ◽  
Daihua Zhang ◽  
Chongwu Zhou

ABSTRACTIn this paper, we present our recent studies on the synthesis and magnetoresistance of single crystalline Fe3O4 core-shell nanowires and nanotubes. Homogeneous Fe3O4 nanowires/tubes with controllable length, diameter and wall thickness were synthesized. The as-prepared material composition and stoichoimetry have been carefully examined and confirmed with a variety of characterization techniques including XRD, EDS, XPS, and TEM. Magnetoresistance under different temperatures was systemically studied. Up to 1.2% room temperature magnetoresistance was observed in the as synthesized nanowires/tubes under a magnetic field of B = 1.8 T.


RSC Advances ◽  
2015 ◽  
Vol 5 (3) ◽  
pp. 1684-1689 ◽  
Author(s):  
Bo-Tau Liu ◽  
Shao-Xian Huang ◽  
Mei-Feng Lai ◽  
Zung-Hang Wei

Transparent conductive films with high anisotropic conductivity ratio (>105) were prepared from Ag–Ni core–shell nanowires by applying a magnetic field.


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