Robust topological phase in proximitized core–shell nanowires coupled to multiple superconductors

• Tudor D. Stanescu,
• Anna Sitek and
• Andrei Manolescu

Beilstein J. Nanotechnol. 2018, 9, 1512–1526, doi:10.3762/bjnano.9.142

• Science and Engineering, Reykjavik University, Menntavegur 1, IS-101 Reykjavik, Iceland 10.3762/bjnano.9.142 Abstract 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

• longitudinal magnetic field. The system is predicted to host zero-energy Majorana modes localized at the two ends of the nanowire [5][7][8]. These zero-energy states combine equal proportions of electrons and holes and are created by second quantized operators satisfying the “Majorana condition” γ† = γ. The

Excitation of nonradiating magnetic anapole states with azimuthally polarized vector beams

• Aristeidis G. Lamprianidis and
• Andrey E. Miroshnichenko

Beilstein J. Nanotechnol. 2018, 9, 1478–1490, doi:10.3762/bjnano.9.139

• useful applications in biosensing, i.e., in the detection of molecules that interact strongly once exposed to magnetic field hotspots, which nanoparticles in a magnetic anapole state can offer in their near field. Moreover, the signal-to-noise ratio of an MRI machine, that is defined as the ratio of the

• , leading to a scattering dip of less than −30 dB between two, hexadecapolar and quadrupolar, resonances. In Supporting Information File 1, one can find a plot with the proposed phase-modulation mask, together with some electric and magnetic field plots that correspond to the illumination of a silicon

• wave and the formulas with which the elements of the T-matrix are calculated based on the EBCM method. It also includes a plot of the proposed phase mask for Figure 1c, electric and magnetic field plots corresponding to the anapole condition discussed in Figure 1b and Figure 1c, and some extra 2D plots

Cr(VI) remediation from aqueous environment through modified-TiO₂-mediated photocatalytic reduction

• Rashmi Acharya,
• Brundabana Naik and
• Kulamani Parida

Beilstein J. Nanotechnol. 2018, 9, 1448–1470, doi:10.3762/bjnano.9.137

• overlap of the TiO2 band with that of Fe3O4 and (iii) efficient separation and recyclability of the catalyst under application of an external magnetic field because of the presence of magnetic Fe3O4. Therefore, the composite photocatalysts exhibited a higher rate of photoreduction of Cr(VI) as compared to

Tailoring polarization and magnetization of absorbing terahertz metamaterials using a cut-wire sandwich structure

• Hadi Teguh Yudistira,
• Shuo Liu,
• Tie Jun Cui and
• Han Zhang

Beilstein J. Nanotechnol. 2018, 9, 1437–1447, doi:10.3762/bjnano.9.136

• relative permeability can be defined as μr = 1 + M / H, where E, H, P, and M are the electric field, magnetic field, polarization, and magnetization [12], respectively. Magnetization and polarization are two factors that can be used to tailor the relative permeability and relative permittivity

• existence of a high absorption when the high electric field and magnetic field are stored on the metamaterial structure. The electric and magnetic field distributions are presented in the inset of Figure 6. The electric field distribution showed that the maximum value of the electric field was at the gap

• between two unit cells. The magnetic field distribution showed that the maximum value of the magnetic field was between layers 1 and 2. The anti-parallel surface in the gold metallic bars on layers 1 and 2 generated magnetization. The maximum value of the electric and magnetic fields was found here, while

Robust midgap states in band-inverted junctions under electric and magnetic fields

• Álvaro Díaz-Fernández,
• Natalia del Valle and
• Francisco Domínguez-Adame

Beilstein J. Nanotechnol. 2018, 9, 1405–1413, doi:10.3762/bjnano.9.133

• up to stage once again with the theoretical prediction by Bernevig et al. [3] of a topological insulating behaviour in a HgTe/CdTe quantum well. The difference between the latter and the quantum Hall system lies in the fact that the quantum well required no magnetic field at all, but just

• symmetry allow us to define a topological index given by the sign of the Dirac mass [21]. In 1994, Agassi studied the case of a band-inverted junction with a magnetic field applied parallel to the junction [23]. This author showed that the Dirac point remains robust upon the application of a magnetic field

• of arbitrary strengths and that the Landau levels in the continuum split for non-zero values of the in-plane momentum in the direction perpendicular to the magnetic field. By means of the modern theory of symmetry-protected topological phases, the protection of the Dirac point can be understood in

Interplay between pairing and correlations in spin-polarized bound states

• Szczepan Głodzik,
• Aksel Kobiałka,
• Anna Gorczyca-Goraj,
• Andrzej Ptok,
• Grzegorz Górski,
• Maciej M. Maśka and
• Tadeusz Domański

Beilstein J. Nanotechnol. 2018, 9, 1370–1380, doi:10.3762/bjnano.9.129

• aligned perpendicularly to the wire and the magnetic field parallel to it, leading to the effective intersite pairing of identical spins and (under specific conditions) inducing zero-energy end modes resembling Majorana quasiparticles. This issue has been recently studied very intensively but here we

• the spin-dependent spectrum ρiσ(ω) as a function of a varying magnetic field. At a critical value (B ≈ 0.2) we observe the emergence of zero-energy quasiparticles, whose spectral weights strongly depend on the spin σ. For a better understanding of the polarized zero-energy quasiparticles, we present

• recently observed by STM spectroscopy with use of a polarized tip [42]. We have studied here the evolution of the polarized quasiparticle states with respect to the magnetic field (Figure 4) and investigated the spatial oscillations of the Majorana zero-energy modes near the chain edges (Figure 5). Finally

Disorder-induced suppression of the zero-bias conductance peak splitting in topological superconducting nanowires

• Jun-Tong Ren,
• Hai-Feng Lü,
• Sha-Sha Ke,
• Yong Guo and
• Huai-Wu Zhang

Beilstein J. Nanotechnol. 2018, 9, 1358–1369, doi:10.3762/bjnano.9.128

• several experiments since 2012 [23][24][25][26][27][28][29][30]. As an important signature of MBSs in the semiconductor nanowires which are proximity-coupled to s-wave superconductors, the zero-bias conductance peak has been observed in the tunneling spectra in the presence of a finite magnetic field [23

• Coulomb island. It is illustrated that the energy splitting is exponentially suppressed with increasing wire length. For short wires with a typical length of a few hundred nanometers, the Majorana energies oscillate as the magnetic field varies. These observations are consistent with previous theoretical

• ][41][42][43]. Secondly, theory predicts an increasing oscillation magnitude of Majorana energy splitting with the increase of magnetic field [36][44], while the experiment indicates the damped oscillation with increasing field. Similar discrepancy was also shown in the Majorana-quantum dot hybrid

Andreev spectrum and supercurrents in nanowire-based SNS junctions containing Majorana bound states

• Jorge Cayao,
• Annica M. Black-Schaffer,
• Elsa Prada and
• Ramón Aguado

Beilstein J. Nanotechnol. 2018, 9, 1339–1357, doi:10.3762/bjnano.9.127

• Hamiltonian of which is given by [38][39][40][41][42][43] where is the momentum operator, μ the chemical potential that determines the filling of the nanowire, αR represents the strength of Rashba spin–orbit coupling, is the Zeeman energy as a result of the applied magnetic field in the x-direction along

• Anderson’s theorem [47]. A finite magnetic field induces a so-called Zeeman depairing, which results in a complete closing of the induced superconducting gap when B exceeds Δ. This is indeed observed in Figure 2b (magenta dash-dot line). Further increasing of the Zeeman field in this normal state gives rise

• is subjected to an external magnetic field (denoted by the black arrow). Superconducting correlations are induced into the nanowire via proximity effect, thus becoming superconducting with the induced pairing potential ΔS < ΔS′. Low-energy spectrum of a superconducting nanowire as function of the

New 2D graphene hybrid composites as an effective base element of optical nanodevices

• Olga E. Glukhova,
• Igor S. Nefedov,
• Alexander S. Shalin and
• Мichael М. Slepchenkov

Beilstein J. Nanotechnol. 2018, 9, 1321–1327, doi:10.3762/bjnano.9.125

• and magnetic field strength, respectively. The host medium is vacuum. In this configuration the wave is p-polarized (or E-wave). To determine the coefficient of reflection, transmission and absorption, Maxwell's equations for the electric and magnetic fields in a vacuum with the 2D CNT–graphene

• composite as an interface have been considered. Assuming a plane-wave solution, Maxwell's equations can be written in the form where E and H are the electric and the magnetic field strength, respectively, k is the wave vector and ω is the frequency of the incident electromagnetic radiation. The following

• of a p-polarized wave: where R and T are the reflection and the transmission coefficient, respectively. Due to continuity of the tangent components of the electric field at the composite surface one can write: For the tangent components of the magnetic field at the composite surface one can write

Induced smectic phase in binary mixtures of twist-bend nematogens

• Anamarija Knežević,
• Irena Dokli,
• Marin Sapunar,
• Suzana Šegota,
• Ute Baumeister and
• Andreja Lesac

Beilstein J. Nanotechnol. 2018, 9, 1297–1307, doi:10.3762/bjnano.9.122

• . The assignment of the NTB phase was further supported by small-angle X-ray diffraction studies on the mixture containing 18 mol % BB as shown in Figure 3. X-ray diffraction measurements of the sample were performed under a magnetic field of 1 T upon cooling (1 K/min) from the isotropic liquid. A

• between adjacent layers [34]. The induction of the smectic phase was confirmed by the presence of an additional peak in the DSC trace and by X-ray diffraction analysis performed on the mixture containing 73 mol % of BB. The diffraction pattern obtained in magnetic field of 1 T upon cooling at 73 °C shows

• texture after shearing the sample at 82 °C, d) 2D XRD patterns for a sample of 73 mol % BB mixture aligned in the magnetic field obtained on cooling from the isotropic liquid at 73 °C. IR spectra of pure BB (red), pure CBI (green) and a 73 mol % BB mixture (blue) at room temperature. IR spectra in the CH2

Formation and development of nanometer-sized cybotactic clusters in bent-core nematic liquid crystalline compounds

• Yuri P. Panarin,
• Sithara P. Sreenilayam,
• Jagdish K. Vij,
• Anne Lehmann and
• Carsten Tschierske

Beilstein J. Nanotechnol. 2018, 9, 1288–1296, doi:10.3762/bjnano.9.121

• (POM) [25], Raman scattering [26][27], XRD [28][29], photon correlation spectroscopy (PCS) [27][30][31] and NMR [32][33]. Recently Kim et al. [29] carried out X-ray experiments on a bent-core system in its nematic phase. They aligned the long molecular axes by applying a strong magnetic field parallel

• around the long axes needs to be broken by aligning one of the short axes or if the long axes need to be subjected to such a strong magnetic field. Can such a large field induce the orientational order parameter greater than its thermodynamic value? Nevertheless it is now clear that many of the

Proximity effect in a two-dimensional electron gas coupled to a thin superconducting layer

• Christopher Reeg,
• Daniel Loss and
• Jelena Klinovaja

Beilstein J. Nanotechnol. 2018, 9, 1263–1271, doi:10.3762/bjnano.9.118

• the application of an out-of-plane magnetic field [4][5] (though orbital effects are not incorporated here) or due to the proximity of a magnetic insulator [8]. Also, it is possible to apply an in-plane magnetic field (to avoid unwanted orbital effects) to reach the topological phase if the 2DEG has a

• finite Dresselhaus SOI, as shown in [9]. An in-plane magnetic field in the presence of only Rashba SOI is not sufficient to reach the topological phase because it does not open a gap in the Rashba spectrum. The spectrum in the presence of the Zeeman splitting, which again is determined by poles in the

Circular dichroism of chiral Majorana states

• Javier Osca and
• Llorenç Serra

Beilstein J. Nanotechnol. 2018, 9, 1194–1199, doi:10.3762/bjnano.9.110

• , to the hybrid devices of [17], consisting of a quantum-anomalous Hall insulator and a superconductor material. In such systems, chiral Majorana modes propagating along the edges in a clockwise or anticlockwise manner, depending on the orientation of a perpendicular magnetic field, are formed at the

• negative. In the limit of a long 2D ribbon there is a preferred CD sign, depending on the magnetic field orientation. For a disc geometry the generalized angular momentum Jz becomes a good quantum number. Then, the combination of circular and particle–hole symmetries in a disc causes a vanishing absorption

• of any chirality preference exactly vanishes. Results and Discussion Chiral bands Figure 1 shows the evolution of the eigenvalue spectrum as a function of the magnetic field parameter ΔB. The results reproduce already known results [17]. At vanishing ΔB the spectrum around zero energy is gapped, a

Inverse proximity effect in semiconductor Majorana nanowires

• Alexander A. Kopasov,
• Ivan M. Khaymovich and
• Alexander S. Mel'nikov

Beilstein J. Nanotechnol. 2018, 9, 1184–1193, doi:10.3762/bjnano.9.109

• separates the regimes with trivial and nontrivial topological properties of the system [3][4][18]. Further increase in the magnetic field is known to suppress the proximity effect since in the absence of the spin–orbit coupling the Fermi level crosses the only energy branch with a complete spin polarization

• along the magnetic field direction. The nonzero spin–orbit coupling destroys this spin polarization mixing different spin projections and resulting in a nonzero induced superconducting gap in the wire of approximately αΔind/gβH, where Δind is the induced superconducting order parameter in the wire, and

• α is the spin–orbit coupling constant. Still, even in the presence of the spin–orbit coupling the increasing magnetic field suppresses the induced superconductivity, which definitely restores the superconducting order parameter in the S film. This reentrant superconductivity stimulated by the

Thermoelectric current in topological insulator nanowires with impurities

• Sigurdur I. Erlingsson,
• Jens H. Bardarson and
• Andrei Manolescu

Beilstein J. Nanotechnol. 2018, 9, 1156–1161, doi:10.3762/bjnano.9.107

• charge current generated by maintaining a temperature difference over a nanowire at zero voltage bias. For topological insulator nanowires in a perpendicular magnetic field the current can change sign as the temperature of one end is increased. Here we study how this thermoelectric current sign reversal

• depends on the magnetic field and how impurities affect the size of the thermoelectric current. We consider both scalar and magnetic impurities and show that their influence on the current are quite similar, although the magnetic impurities seem to be more effective in reducing the effect. For moderate

• insulator material, such as BiSe, is formed into a nanowire, topological states can appear on its surface. Recently, such wires in a magnetic field have been studied extensively both theoretically [20][21][22][23][24] and experimentally [5][6][7][8][9][10][25]. When the nanowires are of circular cross

Field-controlled ultrafast magnetization dynamics in two-dimensional nanoscale ferromagnetic antidot arrays

• Anulekha De,
• Sucheta Mondal,
• Sourav Sahoo,
• Saswati Barman,
• Yoshichika Otani,
• Rajib Kumar Mitra and
• Anjan Barman

Beilstein J. Nanotechnol. 2018, 9, 1123–1134, doi:10.3762/bjnano.9.104

• micromagnetic simulations have been exploited to study the magnetization precession and spin-wave modes of the antidot lattice with varying lattice constant and in-plane orientation of the bias-magnetic field. A remarkable variation in the spin-wave modes with the orientation of in-plane bias magnetic field is

• ], spin-wave filters [14], spin-logic [15] and reprogrammable magnonic devices [16]. The edges of the antidots lead to quantization of SW modes due to lateral confinement as well as the generation of a periodically modulated internal magnetic field due to the demagnetization effect. A number of parameters

• mode structures as well as the anisotropy in the frequency spectra [25]. Quantized SW modes have been found to be transformed to propagating ones and vice versa in rhombic antidot lattices with the variation of the in-plane orientation of the bias-magnetic field [26]. A particular study showed the

Review on nanoparticles and nanostructured materials: history, sources, toxicity and regulations

• Jaison Jeevanandam,
• Ahmed Barhoum,
• Yen S. Chan,
• Alain Dufresne and
• Michael K. Danquah

Beilstein J. Nanotechnol. 2018, 9, 1050–1074, doi:10.3762/bjnano.9.98

• magnets, so-called ferrofluids, are ultrastable suspensions of small magnetic NPs with superparamagnetic properties [36]. Upon applying a magnetic field, the liquid will macroscopically magnetize, which leads to the alignment of NPs along the magnetic field direction [37]. Recent research has focused on

Magnetic characterization of cobalt nanowires and square nanorings fabricated by focused electron beam induced deposition

• Federico Venturi,
• Gian Carlo Gazzadi,
• Amir H. Tavabi,
• Alberto Rota,
• Rafal E. Dunin-Borkowski and
• Stefano Frabboni

Beilstein J. Nanotechnol. 2018, 9, 1040–1049, doi:10.3762/bjnano.9.97

• using beam energies of 5 and 15 keV have the characteristics of magnetic dipoles, with larger magnetic moments observed for NWs deposited at lower energy. L-TEM is used to image magnetic domain walls in NWs and nanorings and their motion as a function of applied magnetic field. The NWs are found to have

• holography (EH) [22]. Here, we use different techniques and different magnetization conditions to investigate the magnetic states of NWs and square nanorings formed from four NWs. The magnetization states of the square nanorings are studied both in the presence of an applied magnetic field and at remanence

• images were taken underfocus in low magnification mode, using the objective mini-lens as the imaging lens, with the objective lens slightly excited (at 10% of the value used for eucentric focus), in order to impart a specimen-tilt-angle-dependent magnetic field to the sample. Off-axis electron holography

Non-equilibrium electron transport induced by terahertz radiation in the topological and trivial phases of Hg_1−xCd_xTe

• Alexandra V. Galeeva,
• Alexey I. Artamkin,
• Alexey S. Kazakov,
• Sergey N. Danilov,
• Sergey A. Dvoretskiy,
• Nikolay N. Mikhailov,
• Ludmila I. Ryabova and
• Dmitry R. Khokhlov

Beilstein J. Nanotechnol. 2018, 9, 1035–1039, doi:10.3762/bjnano.9.96

• inverted band structure (topological phase). Hall effect measurements have shown that all the samples are of the n-type. Free electron concentration values determined in magnetic field of 0.05 T at T = 4.2 K are in the range from 3.7 × 1014 cm−3 to 5.2 × 1014 cm−3. Within the two-band Kane model, the given

Single-crystalline FeCo nanoparticle-filled carbon nanotubes: synthesis, structural characterization and magnetic properties

• Rasha Ghunaim,
• Maik Scholz,
• Christine Damm,
• Bernd Rellinghaus,
• Rüdiger Klingeler,
• Bernd Büchner,
• Michael Mertig and
• Silke Hampel

Beilstein J. Nanotechnol. 2018, 9, 1024–1034, doi:10.3762/bjnano.9.95

• ) were heated to a temperature of 900 °C with a heating rate of 5 K/min followed by an isothermal of 15 min under air atmosphere with a flow rate of 100 mL/min. The magnetic field dependence of the magnetization at 5 K and 300 K in an external magnetic field up to ±5 T was measured by means of

• diffraction peaks for the corresponding oxides were observed as shown by XRD measurements. Magnetic properties The magnetic field dependence of the magnetization M(H) has been measured for the as-prepared and annealed samples of Fe50Co50@CNT prepared by both filling approaches as shown in Figure 7a and Figure

• shielded by the carbon shell. To be specific, the presence of oxide layers would imply the presence of an antiferromagnetic shell around the ferromagnetic cores, i.e., the material would evolve the exchange bias effect where nanoparticles cooled under a magnetic field show a significant shift between the

Enzymatically promoted release of organic molecules linked to magnetic nanoparticles

• Chiara Lambruschini,
• Silvia Villa,
• Luca Banfi,
• Fabio Canepa,
• Fabio Morana,
• Annalisa Relini,
• Paola Riani,
• Renata Riva and
• Fulvio Silvetti

Beilstein J. Nanotechnol. 2018, 9, 986–999, doi:10.3762/bjnano.9.92

• nanoparticles (NPs) [1] are a major class of nanoscale materials, which are actively investigated as carriers for targeted drug delivery [2][3]. In this approach, the nanoparticles that are carrying the appropriate drug are remotely directed to the disease site by means of a magnetic field gradient. Then the

• -superconducting quantum interference device (SQUID) magnetometer (Magnetic Properties Measurement System, Quantum Design) with resolution better than 10−7 emu. The room temperature magnetic hysteresis cycles were obtained in the 0–5 Tesla μ0H magnetic field range. DLS measurements were performed using a Zetasizer

Heavy-metal detectors based on modified ferrite nanoparticles

• Urszula Klekotka,
• Ewelina Wińska,
• Elżbieta Zambrzycka-Szelewa,
• Dariusz Satuła and
• Beata Kalska-Szostko

Beilstein J. Nanotechnol. 2018, 9, 762–770, doi:10.3762/bjnano.9.69

• of the spectral lines is much smaller than in the other cases. An especially wide spectrum is observed in the case of magnetite doped by Mn atoms. The value of the average hyperfine magnetic field on the iron atoms is highest on the sample with Co dopant. The second characteristic feature is the

Anchoring Fe₃O₄ nanoparticles in a reduced graphene oxide aerogel matrix via polydopamine coating

• Błażej Scheibe,
• Radosław Mrówczyński,
• Natalia Michalak,
• Karol Załęski,
• Michał Matczak,
• Mateusz Kempiński,
• Zuzanna Pietralik,
• Mikołaj Lewandowski,
• Stefan Jurga and
• Feliks Stobiecki

Beilstein J. Nanotechnol. 2018, 9, 591–601, doi:10.3762/bjnano.9.55

• and compressed aerogel structures (this sample is further referred as c-rGO-PDA@Fe3O4). The magnetization curves are presented in Figure 7. The room temperature magnetization dependences on the magnetic field (M–H curves) for rGO-Fe3O4, rGO-PDA@Fe3O4 and c-rGO-PDA@Fe3O4 aerogels are shown in Figure 7a

• to 350 K. The magnetic hysteresis loops (M–H dependences) were measured at RT at a magnetic field varying between ±30 kOe. Powder X-ray diffraction (XRD) studies of source materials were carried out to determine the crystallographic structure of the studies compounds. The diffractometer (PANalytical

• allow for direct comparison). Room temperature M–H curves of rGO-Fe3O4, rGO-PDA@Fe3O4 and c-rGO-PDA@Fe3O4 aerogels (a). The inset in (a) presents M–H curves at low magnetic field. ZFC and FC temperature dependences of susceptibility for rGO, rGO-PDA@Fe3O4 and c-rGO-PDA@Fe3O4 aerogels under the applied

Revealing the interference effect of Majorana fermions in a topological Josephson junction

• Jie Liu,
• Tiantian Yu and
• Juntao Song

Beilstein J. Nanotechnol. 2018, 9, 520–529, doi:10.3762/bjnano.9.50

• , respectively. Moreover, α, β are the spin indices, t is the hopping amplitude, μ is the chemical potential, UR is the Rashba coupling strength, and Vx is the Zeeman energy caused by magnetic field along the wire direction. Δ is the superconducting pairing amplitude and Vimp(i) is the Gaussian impurity. Hc

Engineering of oriented carbon nanotubes in composite materials

• Razieh Beigmoradi,
• Abdolreza Samimi and
• Davod Mohebbi-Kalhori

Beilstein J. Nanotechnol. 2018, 9, 415–435, doi:10.3762/bjnano.9.41

• molecular structure of the liquid crystal (LC) (i.e., that it can be simply oriented in the direction of an applied electric or magnetic field) the alignment and dispersion of the CNTs in a solution of liquid crystals is also achievable (Figure 15). The biggest advantage of this method is that small fields

• . This method is also used to produce electrical contacts with individual CNTs [28][106][107]; and recently, the ability of the technique has been investigated to purify metallic SWCNTs from the mixture species [106]. Magnetic field The alignment of CNTs using a magnetic field is a unique technique

• because of its remote action. One of the most common methods to apply a magnetic field is to cast the suspension of CNTs onto a substrate that is placed in the vicinity of a magnet. While the layer on the substrate is drying, CNTs are aligned in the direction of the magnetic field. In this case, unlike an