## Search

Now showing items 1-10 of 130

JavaScript is disabled for your browser. Some features of this site may not work without it.

AuthorSchwingenschlögl, Udo (55)Manchon, Aurelien (43)Zhang, Xixiang (13)Cheng, Yingchun (12)Singh, Nirpendra (9)View MoreDepartmentPhysical Sciences and Engineering (PSE) Division (122)Materials Science and Engineering Program (112)Computational Physics and Materials Science (CPMS) (34)Imaging and Characterization Core Lab (11)Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division (8)View MoreJournal

Physical Review B (130)

KAUST Acknowledged Support UnitOffice of Sponsored Research (OSR) (2)KAUST Supercomputing Centre (1)Office of Sponsored Research (1)Office of Sponsored Research OSR (1)Supercomputing Laboratory at KAUST (1)KAUST Grant NumberOSR-CRG URF/1/1693-01 (3)OSR-2015-CRG4-2626 (2)BAS/1/1626-01-01 (1)BAS/1626-01-01 (1)CRF-2015-SENSORS-2708 (1)View MorePublisherAmerican Physical Society (APS) (128)American Physical Societyrevtex@aps.org (2)TypeArticle (130)Year (Issue Date)2019 (9)2018 (8)2017 (13)2016 (18)2015 (13)View MoreItem Availability
Open Access (130)

Now showing items 1-10 of 130

- List view
- Grid view
- Sort Options:
- Relevance
- Title Asc
- Title Desc
- Issue Date Asc
- Issue Date Desc
- Submit Date Asc
- Submit Date Desc
- Results Per Page:
- 5
- 10
- 20
- 40
- 60
- 80
- 100

Anisotropic planar Hall effect in the type-II topological Weyl semimetal
WTe2

Li, Peng; Zhang, Chenhui; Wen, Yan; Cheng, Long; Nichols, George; Cory, David G.; Miao, Guo-Xing; Zhang, Xixiang (Physical Review B, American Physical Society (APS), 2019-11-20) [Article]

The giant planar Hall effect arising from a chiral anomaly, and that is related to the Berry curvature, has been predicted but never observed in nonmagnetic type-II Dirac/Weyl semimetals. Here, we report an observation of the anisotropic planar Hall effect in type-II Weyl semimetal WTe 2 . Interestingly, we observe a chiral-anomaly-induced sinusoidal angular-dependent planar Hall effect when the electric field is parallel to the tilting direction of Weyl cone, i.e., the b axis of WTe2.The planar Hall effect amplitude is linearly dependent on the magnetic fields and decreases gradually as the temperature increases across the topological phase transition temperature. Our observations clearly reveal the footprints on transport from the chiral anomaly feature in type-II Weyl semimetals.

Quantum anomalous Hall effect and Anderson-Chern insulating regime in the noncollinear antiferromagnetic 3Q state

Ndiaye, Papa Birame; Abbout, Adel; Goli, V. M. L. D. P.; Manchon, Aurelien (Physical Review B, American Physical Society (APS), 2019-10-28) [Article]

We investigate the emergence of both quantum anomalous Hall and disorder-induced Anderson-Chern insulating phases in two-dimensional hexagonal lattices, with an antiferromagnetically ordered 3Q state and in the absence of spin-orbit coupling. Using tight-binding modeling, we show that such systems display not only a spin-polarized edge-localized current, the chirality of which is energy dependent, but also an impurity-induced transition from trivial metallic to topological insulating regimes, through one edge mode plateau. We compute the gaps' phase diagrams and demonstrate the robustness of the edge channel against deformation and disorder. Our study hints at the 3Q state as a promising building block for dissipationless spintronics based on antiferromagnets.

Corner states in a second-order acoustic topological insulator as bound states in the continuum

Chen, Zeguo; Xu, Changqing; Al Jahdali, Rasha; Mei, Jun; Wu, Ying (Physical Review B, American Physical Societyrevtex@aps.org, 2019-08-09) [Article]

A second-order topological insulator is designed on a platform of a two-dimensional (2D) square lattice with all coupling coefficients having the same sign. Simulated results show the existence of two types of nontrivial corner states in this system, with one type being identified as bound states in the continuum (BIC). The non-BIC corner states are also found by surrounding a nontrivial sample by a trivial one, and interestingly, these perfectly confined corner states can be gradually delocalized and merge into edge states by tuning the intersystem coupling coefficient. Both BIC and non-BIC corner states originate from bulk dipole moments rather than quantized quadrupole moments, with the corresponding topological invariant being the 2D Zak phase. Full wave simulations based on realistic acoustic waveguide structures are demonstrated. Our proposal provides an experimentally feasible platform for the study of the interplay between BIC and a high-order topological insulator, and the evolution from corner states to edge states.

First-principles methodology for determining the angular momentum of excitons

Zang, Xiaoning; Schwingenschlögl, Udo (Physical Review B, American Physical Societyrevtex@aps.org, 2019-07-15) [Article]

We develop a methodology for extracting the Kohn-Sham angular momentum of excitons in realistic systems from time-dependent density functional theory. For small systems the exciton populations can be calculated analytically, which allows us to test the methodology for a three-arm H2 molecular ring and a pair of such rings. For larger systems the developed methodology opens a venue to determine the angular momentum of excitons by first principles calculations. A chain of twenty three-arm H2 molecular rings and a triphenylphosphine molecule are investigated as illustrative examples. It is demonstrated that the angular momentum is conserved during the absorption of twisted light.

Magnetically tunable multiband near-field radiative heat transfer between two graphene sheets

Ge, Lixin; Gong, Ke; Cang, Yuping; Luo, Yongsong; Shi, Xi; Wu, Ying (Physical Review B, American Physical Society (APS), 2019-07-11) [Article]

Near-field radiative heat transfer (NFRHT) is strongly related with many applications such as near-field imaging, thermo-photovoltaics and thermal circuit devices. The active control of NFRHT is of great interest since it provides a degree of tunability by external means. In this work, a magnetically tunable multiband NFRHT is revealed in a system of two suspended graphene sheets at room temperature. It is found that the single-band spectra for B=0 split into multiband spectra under an external magnetic field. Dual-band spectra can be realized for a modest magnetic field (e.g., B=4T). One band is determined by intraband transitions in the classical regime, which undergoes a blue shift as the chemical potential increases. Meanwhile, the other band is contributed by inter-Landau-level transitions in the quantum regime, which is robust against the change of chemical potentials. For a strong magnetic field (e.g., B=15T), there is an additional band with the resonant peak appearing at near-zero frequency (microwave regime), stemming from the magnetoplasmon zero modes. The great enhancement of NFRHT at such low frequency has been little reported. This work may pave a way for multiband thermal information transfer based on atomically thin graphene sheets.

Nonequilibrium spin density and spin-orbit torque in a three-dimensional topological insulator/antiferromagnet heterostructure

Ghosh, Sumit; Manchon, Aurelien (Physical Review B, American Physical Society (APS), 2019-07-10) [Article]

We study the behavior of nonequilibrium spin density and spin-orbit torque in a topological insulator/antiferromagnet heterostructure. Unlike ferromagnetic heterostructures where the Dirac cone is gapped due to time-reversal symmetry breaking, here the Dirac cone is preserved. We demonstrate the existence of a staggered spin density corresponding to a dampinglike torque which is quite robust against scalar impurities when the transport energy is such that the transport is confined to the topological insulator surface. We show the contribution to the nonequilibrium spin density due to both surface and bulk topological insulator bands. Finally, we show that the torques in topological insulator/antiferromagnet heterostructures exhibit an angular dependence that is consistent with the standard spin-orbit torque obtained in Rashba system with some additional structure arising from the interfacial coupling.

Current-driven skyrmion depinning in magnetic granular films

Salimath, Akshaykumar; Abbout, Adel; Brataas, A.; Manchon, Aurelien (Physical Review B, American Physical Society (APS), 2019-03-12) [Article]

We consider current-driven motion of magnetic skyrmions in granular magnetic films. The study uses micromagnetic modeling and phenomenological analysis based on the Thiele formalism. Remarkably, the disorder enhances the effective skyrmion Hall effect that depends on the magnitude of the driving force (the cur- rent density and nonadiabaticity parameter). The origin is the sliding motion of the skyrmion along the grain boundaries, followed by pinning and depinning at the grain junctions. A side jump can occur during this depinning process. In addition, the critical current that triggers the skyrmion motion depends on the relative size of the crystallites with respect to the skyrmion size. Finally, when the skyrmion trajectory is confined along an edge by the nonadiabatic Magnus force, the critical current density can be significantly reduced. Our results imply that narrow nanowires exhibit higher skyrmion mobilities.

Origin of the transition entropy in vanadium dioxide

Mellan, Thomas A.; Wang, Hao; Schwingenschlögl, Udo; Grau-Crespo, Ricardo (Physical Review B, American Physical Society (APS), 2019-02-26) [Article]

The reversible metal-insulator transition in VO2 at Tc≈340 K has been closely scrutinized yet its thermodynamic origin remains ambiguous. We discuss the origin of the transition entropy by calculating the electron and phonon contributions at Tc using density functional theory. The vibration frequencies are obtained from harmonic phonon calculations, with the soft modes that are imaginary at zero temperature renormalized to real values at Tc using experimental information from diffuse x-ray scattering at high-symmetry wave vectors. Gaussian process regression is used to infer the transformed frequencies for wave vectors across the whole Brillouin zone, and in turn compute the finite temperature phonon partition function to predict transition thermodynamics. Using this method, we predict the phase transition in VO2 is driven 5 to 1 by phonon entropy over electronic entropy, and predict a total transition entropy that agrees (within 5%) with the calorimetric value.

Local order in Cr-Fe-Co-Ni: Experiment and electronic structure calculations

Schönfeld, B.; Sax, C. R.; Zemp, J.; Engelke, M.; Boesecke, P.; Kresse, Thomas; Boll, T.; Al-Kassab, Tala'at; Peil, O. E.; Ruban, A. V. (Physical Review B, American Physical Society (APS), 2019-01-18) [Article]

A quenched-in state of thermal equilibrium (at 723 K) in a single crystal of Cr-Fe-Co-Ni close to equal atomic percent was studied. Atom probe tomography revealed a single-phase state with no signs of long-range order. The presence of short-range order (SRO) was established by diffuse x-ray scattering exploiting the variation in scattering contrast close to the absorption edges of the constituents: At the incoming photon energies of 5969, 7092, and 8313 eV, SRO maxima that result from the linear superposition of the six partial SRO scattering patterns, were always found at X position. Electronic structure calculations showed that this type of maximum stems from the strong Cr-Ni and Cr-Co pair correlations, that are furthermore connected with the largest scattering contrast at 5969 eV. The calculated effective pair interaction parameters revealed an order-disorder transition at approximately 500 K to a L12-type (Fe,Co,Ni)3Cr structure. The calculated magnetic exchange interactions were dominantly of the antiferromagnetic type between Cr and any other alloy component and ferromagnetic between Fe, Co, and Ni. They yielded a Curie temperature (TC) of 120 K, close to experimental findings. Despite the low value of TC, the global magnetic state strongly affects chemical and elastic interactions in this system. In particular, it significantly increases the ordering tendency in the ferromagnetic state compared to the paramagnetic one.

Temperature study of the giant spin Hall effect in the bulk limit of \nβ−W

Chen, Wenzhe; Xiao, Gang; Zhang, Qiang; Zhang, Xixiang (Physical Review B, American Physical Society (APS), 2018-10-08) [Article]

Giant spin Hall effect (GSHE) in heavy metals can convert charge current into spin current with a high efficiency characterized by a spin Hall angle. In this paper, we prepare a set of multilayer systems of β-W/CoFeB/MgO/Ta with the different β-W thickness up to 18 nm. Using a direct-current magneto-transport method and relying on the anomalous Hall effect of CoFeB, we observed a large spin Hall angle of 64% in the bulk limit of β-W solid at room temperature and a weak temperature dependence of the spin Hall angle. Additionally, we also studied the crystal structure, magnetization, magnetic anisotropy, electrical transport, spin diffusion, and interfacial spin current transmission in this exemplary GSHE system over a broad temperature range of 10 to 300 K, which would benefit fundamental studies and potential spintronics applications of β-W.

The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

By default, clicking on the export buttons will result in a download of the allowed maximum amount of items. For anonymous users the allowed maximum amount is 50 search results.

To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.