| 1. |
- Bauch, Thilo, 1972, et al.
(författare)
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High Frequency Properties of Josephson Junctions
- 2019
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Ingår i: Springer Series in Materials Science. - Cham : Springer International Publishing. - 2196-2812 .- 0933-033X. ; 286, s. 513-528
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In this chapter we will discuss the high frequency properties of Josephson junctions. In the first part we review the effect of a large ac perturbation on the current voltage characteristic (IVC) of a Josephson junction. Here we follow closely the original treatment by Barone and Paterno [1]. For large ac perturbations the externally applied microwave frequency (and integer multiples of it) lock to the Josephson oscillation causing distinct current steps at fixed voltage values in the IVC. In the second part we give a short overview on the response of an underdamped Josephson junction to small microwave perturbations. In this case, when the applied microwave frequency is in resonance with the electromagnetic plasma frequency higher levels of this plasma mode get excited. This mechanism, also called resonant activation, leads for instance to a premature switching from the zero voltage state to the finite voltage state of a current biased Josephson junction. This procedure can be exploited to detect the quantized nature, i.e. the quantized energy levels, of the plasma modes. In fact the lowest two quantized energy levels of the plasma resonance mode are the key ingredient of superconducting qubits, such as the phase qubit and the transmon qubit.
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| 2. |
- Golubev, Dmitry, et al.
(författare)
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Josephson Effect in Graphene and 3D Topological Insulators
- 2019
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Ingår i: Springer Series in Materials Science. - Cham : Springer International Publishing. - 2196-2812 .- 0933-033X. ; 286, s. 529-553
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The study of the proximity effect between a superconductor and a semiconductor or an unconventional metal, has lately received a dramatic boost due to the increasing possibilities to manufacture a larger variety of interfaces and materials.
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| 3. |
- Krammel, C. M., et al.
(författare)
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Structural Properties of Bi Containing InP Films Explored by Cross-Sectional Scanning
- 2019
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Ingår i: Springer Series in Materials Science. - Singapore : Springer Singapore. - 2196-2812 .- 0933-033X. ; 285, s. 215-229
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The structural properties of highly mismatched III-V semiconductors with small amounts of Bi are still not well understood at the atomic level. In this chapter, the potential of cross-sectional scanning tunneling microscopy (X-STM) to address these questions is reviewed. Special attention is paid to the X-STM contrast of isovalent impurities in the III-V system, which is discussed on the basis of theoretical STM images of the (110) surface using density functional theory (DFT) calculations. By comparing high-resolution X-STM images with complementary DFT calculations, Bi atoms down to the third monolayer below the InP (110) surface are identified. With this information, the Short-range ordering of Bi is studied, which reveals a strong tendency toward Bi pairing and clustering. In addition, the occurrence of Bi surface segregation at the interfaces of an InP/InP1−xBix/InP quantum well with a Bi concentration of 2.4 % is discussed.
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| 4. |
- Li, Gang, et al.
(författare)
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Quantum Spin Hall States in 2D Bismuth-Based Materials
- 2019
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Ingår i: Springer Series in Materials Science. - Singapore : Springer Singapore. - 2196-2812 .- 0933-033X. ; 285, s. 351-379
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Berrys phase, an inherent constituent of the electronic wave functions, has revolutionarily enriched our understanding of the fundamental states of matter and has triggered the discovery of many interesting phenomena in condensed matter physics, such as quantum charge/spin pumping, polarization, topological insulating phase, etc. Among them, the discovery of the two-dimensional (2D) quantum spin Hall (QSH) states protected by time-reversal symmetry (TRS) boosts the wide interest in the study of topological materials in the past decade. These include the 2D quantum anomalous Hall states (QAH), three-dimensional topological insulators (TIs), Dirac semimetals (SM), and topological nodal-line SMs as well as Weyl SMs. This article by no means can cover everything of this rapidly developing field, we rather focus on the bismuth-based honeycomb materials hosting large-gap QSH/QAH states, which promise applications for room-temperature spintronic. We will explain their topological mechanisms in terms of Berrys phase and topological invariant. After introducing a concrete material example which has been successfully grown in experiment, e.g., Bi/SiC(0001), various theoretical proposals on atom substitution and functionalization based on bismuth honeycomb lattice will then be discussed, from which a general designing principle for achieving large topological gaps can be summarized. This article hopes to stimulate more experimental activities toward the examination of large-gap QSH/QAH theoretical proposals and the potential applications in spintronic devices.
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| 5. |
- Song, Yuxin, 1981, et al.
(författare)
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Dilute Bismides for Mid-IR Applications
- 2013
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Ingår i: Springer Series in Materials Science. - New York, NY : Springer New York. - 2196-2812 .- 0933-033X. - 9781461481218 ; 186, s. 1-27
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Dilute bismides are a group of emerging materials with unique properties. Incorporation of a small amount of Bi in common III–V host materials results in large band-gap reduction and strong spin-orbit splitting, leading to potential applications in mid-infrared (Mid-IR) optoelectronics. In this chapter, we review recent progresses on epitaxy and characterizations of novel bismides, i.e., GaSb1−x Bi x , InSb1 − x Bi x , InAs1 − x Bi x , and InAsSbBi. Although these dilute bismides have been successfully grown, to obtain high Bi incorporations and retain high crystal quality is still very challenging.
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| 6. |
- Tassin, Philippe, 1982, et al.
(författare)
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Field enhancement with classical electromagnetically induced transparency
- 2015
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Ingår i: Springer Series in Materials Science. - Cham : Springer International Publishing. - 2196-2812 .- 0933-033X. ; 200, s. 303-319
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Tidskriftsartikel (refereegranskat)abstract
- A key challenge in the design of tunable and nonlinear metamaterials is creating large local electromagnetic fields to enhance the nonlinear interaction. An attractive way to achieve local field enhancement is the use of metamaterials with dark resonators, i.e., with meta-atoms that do not directly couple to the external field. Such metamaterials exhibit a scattering response that is similar to what is observed for electromagnetically induced transparency (EIT): they combine large group delay with low absorption at the same frequency. Classical EIT metamaterials are interesting for nonlinear metamaterials because of the large field enhancement due to the lack of radiation loss in the dark element and for tunable metamaterials because of the high sensitivity of the resonance to the environment or a control signal. We discuss the design and modeling of EIT metamaterials and some early work on their applications to media with nonlinear/tunable response.
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| 7. |
- Wang, L, et al.
(författare)
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Bismuth-Related Nanostructures
- 2019
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Ingår i: Springer Series in Materials Science. - Singapore : Springer Singapore. - 2196-2812 .- 0933-033X. ; 285, s. 181-199
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Bismuth can modify surface reconstruction of III-V semiconductors and affect their growth conditions. Bismuth incorporation into III-Vs strongly changes their electronic properties. We present an overview of how the above Bi-related effects influence structural and optical properties of III-V nanostructures.
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| 8. |
- Wang, Shu Min, 1963, et al.
(författare)
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Phosphorus and Nitrogen Containing Dilute Bismides
- 2019
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Ingår i: Springer Series in Materials Science. - Singapore : Springer Singapore. - 2196-2812 .- 0933-033X. ; 285, s. 97-123
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Phosphorus and nitrogen containing dilute bismides differ from arsenic and antimony containing bismides in that the anions have large differences in atomic size and electronegativity, offering rich potentials for strain as well as bandgap engineering. In this chapter, we show theoretical modeling, epitaxy and characterizations of III-PBi and III-NBi and their quaternary alloys.
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| 9. |
- Yue, L., et al.
(författare)
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Molecular Beam Epitaxy Growth and Properties of GaAsBi and AlAsBi
- 2019
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Ingår i: Springer Series in Materials Science. - Singapore : Springer Singapore. - 2196-2812 .- 0933-033X. ; 285, s. 11-36
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- GaAsBi alloys have been extensively studied in recent years, and the highest Bi concentration yet reached has been 22 %. Many photoelectric devices using this material have been produced, such as quantum well lasers, LEDs, solar cells, etc. The Bi incorporated into AlAs is expected to change the bandgap from indirect to direct. There are only a few theoretical reports on AlAsBi, however, experimental research results are seldom reported. In this chapter, we review the molecular beam epitaxy of GaAsBi and analyze the growth mechanism. Besides, we present the synthesis of AlAsBi by molecular beam epitaxy. The growth temperature, As/Ga flux ratio, Bi flux and the growth rate all have great influence on the Bi incorporation. Bismuth atoms play a surfactant role under As-rich conditions and an anti-surfactant role under Ga-rich conditions. Droplets tend to be formed on the surface of GaAsBi alloys due to the atomic size mismatch between Bi atoms and As atoms. The high-angle annular dark-field mode of scanning transmission electron microscopy images confirm Bi atoms cluster exsiting in GaAsBi films. Furthermore, we show the optical properties of GaAsBi and discuss the localized states induced by Bi. The photoluminescence wavelength of GaAsBi redshifts with increasing Bi concentration. The bandgap of GaAsBi is insensitive to temperature, which is important for developing un-cooled lasers. We discuss the influence of Bi incorporation on the electric and transport properties of GaAsBi. The types of dominant point defects induced by Bi incorporation are analyzed. The measurement results of the electron effective mass demonstrate that Bi incorporation not only changes the valence band but also has non-negligible influence on the conduction band in GaAsBi. For AlAsBi, we review the theoretical simulations and present the molecular beam epitaxy growth without substrate rotaion to investigate the influence of As/Al flux raio and the Bi flux on Bi incorporation.
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| 10. |
- Jayakumar, O. D., et al.
(författare)
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Experimental and theoretical investigations of dopant, defect, and morphology control on the magnetic and optical properties of transition metal doped ZnO nanoparticles
- 2014
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Ingår i: Springer Series in Materials Science. - New Delhi : Springer Nature. - 0933-033X. ; 180, s. 341-370
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Tidskriftsartikel (refereegranskat)abstract
- The control of size, shape, and physical properties by surface modifications are of immense interest in materials which are of technological importance. The ZnO-based wide bandgap semiconductor nanoparticles have gained significant interest in the research community due to its large exciton binding energy (60 meV). Further substantial renewed interest in ZnO-based compounds is due to the possible realization of p-type conduction and ferromagnetic behavior when doped with transition metals. In this report we present interesting results on the ZnO nanoparticle system in which the control of dopants, morphology, and the surface modification can influence significantly the physical properties of the ZnO nanoparticles. First, we present the methods to control the morphology of the ZnO particle to obtain nanorods. As an example we show the effect of Li dopant on the morphology control of Co and Ni doped ZnO. The effect of morphology on the magnetic properties of these compounds is discussed further. We also demonstrate the effect of the n-type charge carriers on the magnetic and optical properties by doping aliovalent cations in Zn(Co)O. Following this we comment on the magnetic property manipulations by surfactant treatment of transition metal (TM) doped ZnO and defect stabilization in ZnO by Mg doping. The magnetic coupling is RKKY-like both with and without Li co-doping. Finally, we provide the significant implications of these results on the nanorods structures of room temperature ferromagnetic materials by first-principles modeling. These theoretical analyses demonstrate that Li co-doping has primarily two effects in bulk Zn1-xMxO (with M = Co or Ni). First, the Li-on-Zn acceptors increase the local magnetic moment by depopulating the M 3d minority spin-states. Second, Li-on- Zn prefer to be closer to the M atoms to compensate the M-O bonds and to locally depopulate the 3d states, and this will help in forming high aspect nanostructures. The observed room temperature ferromagnetism in Li co-doped Zn1-xMxO nanorods can therefore be explained by the better rod morphology in combination with locally ionizing the magnetic M atoms.
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