Top PDF Transport Signatures of Spin-Orbit Coupling in Graphene-Based Materials

Transport Signatures of Spin-Orbit Coupling in Graphene-Based Materials

Transport Signatures of Spin-Orbit Coupling in Graphene-Based Materials

The above SOC signatures can be possibly identified by the magneto-conductivity (MC) transport experiment[12]. The SOC in conventional 2D electron gas will turn the disorder class from weak-localization (WL) to weak anti-localization (WAL) by changing the quantum interference. However, the contribution of SOC in quantum conductivity is more complicated in graphene due to its unusual chirality [1, 38]. Graphene with smooth disorder is predicted to exhibit WAL [1]; However, strong inter-valley scattering, which typically arises in ordinary-quality samples, suppresses the chirality-related WAL and generates weak localization (WL) [24, 31]. While introducing strong Rashba SOC, the electron spin precesses around the effective magnetic field and acquires an additional π phase in the interference [25]—reviving WAL due to spin. Intrinsic (Kane-Mele) SOC terms, by contrast, break an effective time reversal symmetry and thus place the system in the unitary class (suppressed WL) [25]. Note that the SOC has to strong enough to participate in the interference before the electron dephasing out—i.e. the relaxation rate exceeds the inelastic de- phasing rate. Though intrinsic SOC is the most important SOC to realized quantum spin Hall phase, it is hard to pinpoint its existence by MC since unitary behav- ior can come from not only intrinsic SOC, but also other decoherence sources as well. Therefore, in this work, we investigate the MC signatures in l = p, d-orbital adatom doped graphene, We also proposed a scheme to hunt for the SOC signatures this case and derive the corresponding magneto-conductivity formula and spin- relaxation rates.
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Spin-orbit coupling and electron spin resonance for interacting electrons in carbon nanotubes

Spin-orbit coupling and electron spin resonance for interacting electrons in carbon nanotubes

Evidence for the LL behaviour of interacting 1D electrons has been reported for charge transport in SWNTs [2, 3, 4]. However, in such materials one also expects to find more dramatic consequences of the breakdown of Fermi liquid theory, most notably the phenomenon of spin-charge separation. This many-body effect asserts that electrons brought into a LL effectively break up into a charge and a spin part that travel with different velocities and hence will be spatially separated after some time. A recent proposal to detect evidence for spin-charge separation in SWNTs has been based on spin transport [8]. A different (and perhaps easier to realize) proposal based on electron spin resonance (ESR) is reviewed in this paper, expanding on our short paper [10]. ESR is a valuable experimental tool to probe the intrinsic spin dynamics of many systems. In ESR experiments one applies a static magnetic field and measures the absorption of radiation polarized perpendicular to the field direction. In the absence of SU(2) spin symmetry breaking terms in the Hamiltonian, the absorption intensity is then simply a δ-peak at the Zeeman energy [11, 12].
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Crystal-field effects in graphene with interface-induced spin-orbit coupling

Crystal-field effects in graphene with interface-induced spin-orbit coupling

X = Zr, Hf, and Y = S, Se, Te) and opens up the possibil- ity to observe this coupling in bilayers of these materials and graphene. Less attention has been paid to this family [55,56] compared to group-V and -VI TMDs. The application of Zr-based chalcogenides in solar-energy devices has been suggested [56], and the possibility of tuning its properties by pressure, electric field, and phase engineering was recently explored in density functional theory calculations [57]. Our findings suggest that TMDs of family IV are potential candi- dates to induce nontrivial spin textures in graphene via prox- imity coupling. On the other hand, the anisotropic Bychkov- Rashba coupling requires ǫ xz = ǫ yz , which is only possible in a
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Spin Orbit Coupling Gap and Indirect Gap in Strain Tuned Topological Insulator Antimonene

Spin Orbit Coupling Gap and Indirect Gap in Strain Tuned Topological Insulator Antimonene

Band inversion is a necessary condition for inducing TI phase. Applying strain is one of the methods to cause a band inversion. If spin-orbit coupling (SOC) is ignored, system usually becomes metallic due to the band cross- ing caused by the band inversion between the highest valence band (VBM) and the lowest conduction band (CBM). SOC is the key to opening a gap (SOC gap) at such crossing point to keep the systems remaining insulating in bulk and meet another necessary condition of inducing TI phase. Furthermore, if TI phase is induced, and the bulk band gap is large enough, such a TI phase continues to exist at room temperature and has a small finite size effect [33] and may become one of the promising candidates of spintronic devices.
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Effects of spin orbit coupling and many body interactions on the electronic structure of Sr₂RuO₄

Effects of spin orbit coupling and many body interactions on the electronic structure of Sr₂RuO₄

Photoemission spectroscopy is based on the photoelectric effect discovered by Hertz in 1887 [23]. In the 1880s Hertz was working on the generation and properties of electrical oscillations. His experiments proved the existence of electromagnetic waves, predicted by Maxwell, but also revealed a new phenomenon, the photoelectric effect. Hertz noticed that metal contacts exhibit enhanced ability to spark when exposed to light. Shortly after Hertz published his results, Hallwachs observed that negatively charged plates are loosing their charge when exposed to UV light while positively charged ones do not [24]. The interpretation of these findings was far from trivial as the electron was only discovered a decade after Hallwachs’ experiments. In 1899 J. J. Thomson [25] reported the discovery of new tiny sub-particles with negative charge, later called electrons. Following work of Hertz and Hallwachs in 1902 Lenard [26] performed a series of breakthrough experiments. He measured the energy distribution of photoelectrons by applying a variable retarding potential. From the results he concluded that the number of emitted electrons depends on the intensity of the light and, surprisingly, that their velocity depends only on the light frequency. On the basis of current knowledge at the time Lenard could not explain the relationship between the maximum kinetic energy of electrons and the wavelength of the incident radiation.
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Majorana fermions emerging from magnetic nanoparticles on a superconductor without spin-orbit coupling

Majorana fermions emerging from magnetic nanoparticles on a superconductor without spin-orbit coupling

Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, NL-2300 RA Leiden, The Netherlands (Received 5 August 2011; revised manuscript received 25 October 2011; published 9 November 2011) There exists a variety of proposals to transform a conventional s-wave superconductor into a topological superconductor, supporting Majorana fermion midgap states. A necessary ingredient of these proposals is strong spin-orbit coupling. Here we propose an alternative system consisting of a one-dimensional chain of magnetic nanoparticles on a superconducting substrate. No spin-orbit coupling in the superconductor is needed. We calculate the topological quantum number of a chain of finite length, including the competing effects of disorder in the orientation of the magnetic moments and in the hopping energies, to identify the transition into the topologically nontrivial state (with Majorana fermions at the end points of the chain).
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Density Functional Analysis of the Spin Exchange Interaction and Spin-Orbit Coupling in some Magnetic Oxides of Transition-Metal Elements.

Density Functional Analysis of the Spin Exchange Interaction and Spin-Orbit Coupling in some Magnetic Oxides of Transition-Metal Elements.

The energy-mapping method described above is objective in that, once a set of spin exchange paths is chosen for a magnetic solid, it does not presume whether the associated spin exchange parameters should be FM or AFM. This method simply maps the electronic energy spectrum of DFT+U calculations onto the energy spectrum of the spin Hamiltonian defined by a set of spin exchange parameters. However, the values of the resulting spin exchange parameters depend on what set of exchange paths one selects. In identifying the spin lattice appropriate for a magnetic solid under consideration, therefore, energy-mapping analysis should be carried out for a set of spin exchange paths large enough to include all important ones. In particular, for magnetic solids consisting of both M-O-M and M-O…O-M spin exchange paths, those M-O…O-M paths with short O…O contact distances should not be omitted in the energy-mapping analysis.
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Spin-orbit coupling effects in O(2) activation by cofactor-independent 2,4-dioxygenase

Spin-orbit coupling effects in O(2) activation by cofactor-independent 2,4-dioxygenase

The weak point here is connected with the na- ture of driving force for the spin flip in Eq. (2). Mas- sey made no comments about this. One can propose logically that Massey has taken into account the ideas of RPT [23] which were popular that time. The square brackets in Eq. (2) denote the solvent cage for radical pair which is really big and embraces a micro-part of solvent volume [23]. It means that two radicals can be far separated before their secondary collision and spin evolution proceeds during free dif- fusion of radicals inside solvent cage between two collisions. According to RPT the driving force for spin inversion in such radical pair is represented by very weak electron-nuclear spin-spin interac- tion (hyper­fine coupling, 10 -4 cal/mol) inside each
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Stroboscopic model of transport through a quantum dot with spin-orbit scattering

Stroboscopic model of transport through a quantum dot with spin-orbit scattering

We present an open version of the symplectic kicked rotator as a stroboscopic model of electrical conduction through an open ballistic quantum dot with spin-orbit scattering. We demonstrate numerically and analytically that the model reproduces the universal weak localization and weak antilocalization peak in the magnetocon- ductance, as predicted by random-matrix theory 共 RMT 兲 . We also study the transition from weak localization to weak antilocalization with increasing strength of the spin-orbit scattering, and find agreement with RMT. DOI: 10.1103/PhysRevB.72.235305 PACS number 共 s 兲 : 73.63.Kv, 05.45.Pq, 71.70.Ej, 73.20.Fz
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Charge and Spin Carrier Transport in Graphene and its Derivatives.

Charge and Spin Carrier Transport in Graphene and its Derivatives.

In a short summary, we estimated the probability of transmission through the rectan- gular potential step and the barrier, if the electron-phonon scattering is included in the consideration. The correction to the ideal case (i.e., no EPC) was calculated in the first order of the TDPT. We demonstrated that, by the most conservative estimates, the size of the device that takes advantage of the electron’s pseudospin degree of freedom in MLG, can be of the order of 10 µm, if EPC is the dominant scattering mechanism. Beyond this threshold, the tunneling probability at normal incidence can drop from unity to below 90%. At the same time, the calculations show that in case of such large devices the first order of TDPT provides a limited accuracy as the electron becomes more likely to be scattered more than once. The indicator of the insufficiency of the first order in the perturbation theory expansion is the norm defined in Eq. (5.69): a substantial deviation of N from unity is the evidence a low accuracy of such approximation. However, our estimations of N show that the obtained tunneling probabilities provide a correct semi- quantitative picture even in the extreme cases of larger L and E k . This claim is based on
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Wavevector-dependent spin filtering and spin transport through magnetic barriers in graphene

Wavevector-dependent spin filtering and spin transport through magnetic barriers in graphene

In this paper we shall focus on the effects of Zeeman and exchange spin splitting and postpone the interesting problem of spin-orbit coupling to a future work. We show that the spin-resolved transmissions exhibit a strong de- pendence on the incidence angle, which allows in princi- ple for a selective transmission of spin-up and spin-down electrons. This effect can be qualitatively understood by a simple semiclassical argument. The bending of the elec- tron trajectories under the barrier depends on the energy and thus, in the presence of spin splitting, is different for the two spin projections. The magnitude of the polariza- tion that can be achieved depends on the spin splitting and can be very large in the presence of a large split- ting, as, e.g., that originating from a proximity-induced exchange field. Moreover, in a resonant double barrier configuration, the polarization can be enhanced by in- creasing the distance between the barriers. In this case, in fact, even for relatively small splitting there exists an energy range where the polarization reaches values close to one for large enough distance.
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Role of nuclear spin-orbit coupling on the constitution of the outer crust of a nonaccreting neutron star

Role of nuclear spin-orbit coupling on the constitution of the outer crust of a nonaccreting neutron star

Abstract. The role of the nuclear spin-orbit coupling on the equilibrium composition and on the equation of state of the outer crust of a nonaccreting neutron star is studied by employing a series of three different nuclear mass models based on the self-consistent Hartree-Fock-Bogoliubov method.

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First principles study of spin dependent transport through graphene/BNC/graphene structure

First principles study of spin dependent transport through graphene/BNC/graphene structure

In order to investigate the effect of the size of graphene flakes on the magnetic orderings, we first consider the three BNC structures under periodic boundary conditions for all directions. Figure 1 shows the computational mod- els employed here, where 64 atoms are included in the supercell and the number of boron atoms is larger than that of nitrogen atoms. The number of k point used in the two-dimensional Brillouin zone integration is 16. For all the calculations in this paper, a repeating sheet model is separated by 17.0 bohr in each layer. The lattice con- stant is 2.67 bohr, which is obtained by the bond length of the graphene sheet. Structural optimization is performed until the remaining forces are less than 0.08 eV/bohr. Table 1 shows the calculated magnetic moments of the BNC structures. The bottom panels of Figure 1 illustrate the difference between up-spin and down-spin charge- density distributions n ↑ (r) − n ↓ (r) of the BNC structures. The BNC sheet with the smallest graphene flake is found to be the largest magnetic moment, and the spin-polarized charge-density distribution accumulates at the graphene flake region.
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A review of graphene materials based sensors

A review of graphene materials based sensors

[69] Cuong, T. V., Pham, V. H., Chung, J. S., Shin, E. W., Yoo, D. H., Hahn, S. H. & Kohl, P. A. (2010). Solution-processed ZnO-chemically converted graphene gas sensor. Materials Letters, 64(22), 2479-2482. [70] Uddin, A. I., Phan, D. T., & Chung, G. S. (2015). Low temperature acetylene gas sensor based on Ag nanoparticles-loaded ZnO-reduced graphene oxide hybrid. Sensors and Actuators B: Chemical, 207, 362-369. [71] Sridevi, S., Vasu, K. S., Bhat, N., Asokan, S., & Sood, A. K. (2016). Ultra sensitive NO2 gas detection using the reduced graphene oxide coated etched fiber Bragg gratings. Sensors and Actuators B: Chemical, 223, 481-486. [72] Su, P. G., & Yang, L. Y. (2016). NH3 gas sensor based on Pd/SnO2/RGO ternary composite operated at room-temperature. Sensors and Actuators B: Chemical, 223, 202-208.
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Landau levels, edge states, and strained magnetic waveguides in graphene monolayers with enhanced spin-orbit interaction

Landau levels, edge states, and strained magnetic waveguides in graphene monolayers with enhanced spin-orbit interaction

We now consider two different SOI parameter sets consistent with the estimates in Ref. 12, and show the complete evolution of the Landau levels from the weak- to the strong-field limit. In Fig. 1, numerical results for the few lowest-energy Landau levels are depicted for ∆ > λ/2, corresponding to a QSH phase for B = 0. The (valley-degenerate) spin-split levels corresponding to the ∆ = λ = b = 0 zero mode exhibit a zero-energy crossing at B ≈ 11 T for the chosen SOI parameters. This crossing signals a quantum phase transition from the QSH phase, which survives for sufficiently small B and ∆ > λ/2, to a peculiar QH phase for large B. As we discuss in Sec. IV, one then again has helical edge states 20
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Proper Definition of Spin Current in Spin-Orbit Coupled Systems

Proper Definition of Spin Current in Spin-Orbit Coupled Systems

Generating pure spin current by applying electric field Present in non-magnetic semiconductors?. Mechanisms:.[r]

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Emergent Magnetic Degeneracy in Iron Pnictides due to the Interplay between Spin-Orbit Coupling and Quantum Fluctuations

Emergent Magnetic Degeneracy in Iron Pnictides due to the Interplay between Spin-Orbit Coupling and Quantum Fluctuations

Recent experiments in iron pnictide superconductors reveal that, as the putative magnetic quantum critical point is approached, different types of magnetic order coexist over a narrow region of the phase diagram. Although these magnetic configurations share the same wave vectors, they break distinct symmetries of the lattice. Importantly, the highest superconducting transition temperature takes place close to this proliferation of near-degenerate magnetic states. In this Letter, we employ a renormalization group calculation to show that such a behavior naturally arises due to the effects of spin-orbit coupling on the quantum magnetic fluctuations. Formally, the enhanced magnetic degeneracy near the quantum critical point is manifested as a stable Gaussian fixed point with a large basin of attraction. Implications of our findings to the superconductivity of the iron pnictides are also discussed.
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Spin-orbit interaction in InSb nanowires.

Spin-orbit interaction in InSb nanowires.

The standard method to extract SOI strength in extended regions is through low-field magnetoconductance (MC) mea- surements [21,22]. Quantum interference (see Fig. 1) in the presence of a strong SOI results in an increased conductance, called weak antilocalization (WAL) [23], that reduces to its classical value when a magnetic field is applied [24]. From fits of MC data to theory a spin relaxation length is extracted. If spin relaxation results from inversion asymmetry, a spin precession length and SOI strength can be defined. To extract SOI strength in nanowires the theory should contain (1) the length over which the electron dephases in the presence of a magnetic field, the magnetic dephasing length [25], and (2) the relation between spin relaxation and spin precession length [26]. The magnetic dephasing and spin relaxation length depend on, besides magnetic field and SOI strength, respectively, dimensionality and confinement. For instance, in nanowires, the spin relaxation length increases when the wire diameter is smaller than the spin precession length [26–28]. Therefore, the spin relaxation length extracted from WAL is not a direct measure of SOI strength. These effects have been studied in 2D wires [25,26], but results for 3D wires are lacking. As geometry and dimensionality are different (see Fig. 1), using 2D results for 3D wires is unreliable. Thus, a theory for 3D wires has to be developed.
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Spin Force on Pseudo Spin Current in Graphene

Spin Force on Pseudo Spin Current in Graphene

Abstract The present study investigated spin force by using pseudo spin-orbit coupling in an artificial atomic structure for graphene. This spin force, which is applied on pseudo spin current, can be controlled by graphene gap and electric field due to charged nanodot. It seems that, by this force can be constructed a logical system from graphene and semiconductors. In addition, this force can be used for understanding the Zitterbewegung of electron wave packet with pseudo spin-orbit coupling in graphene and create of the charge Hall effect in semiconductors and graphene.
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Low-energy theory and RKKY interaction for interacting quantum wires with Rashba spin-orbit coupling

Low-energy theory and RKKY interaction for interacting quantum wires with Rashba spin-orbit coupling

For the benefit of the focussed reader, we briefly sum- marize the main results of our analyis. The effective low- energy theory of an interacting Rashba quantum wire is given in Eq. (29), with the velocities (30) and the di- mensionless interaction parameters (31). Previous theo- ries did not fully account for the e-e backscattering pro- cesses, and the conspiracy of these processes with the broken SU (2) invariance due to spin-orbit effects leads to K s < 1 in Eq. (31). This in turn implies novel ef-

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