Phase diagram of a frustrated asymmetric ferromagnetic spin ladder

We perform a systematic investigation on the ground state of an asymmetric two-leg spin ladder (where exchange couplings of the legs are unequal) with ferromagnetic (FM) nearest-neighbor interaction and diagonal anti-ferromagnetic frustration using the Density Matrix Renormalization Group (DMRG) method. When the ladder is strongly asymmetric with moderate frustration, a magnetic canted state is observed between a FM state and a singlet dimerized state. The phase boundaries are dependent on the asymmetric strength $\alpha_{a}$. On the other hand, when the asymmetric strength is intermediate, a so-called spin-stripe state (spins align parallel on same legs, but antiparallel on rungs) is discovered, and the system experiences a first-order phase transition from the FM state to the spin-stripe state upon increasing frustration. We present numerical evidence to interpret the phase diagram in terms of frustration and the asymmetric strength.Comment: 14 pages, 8 figure

The Role of IS Capabilities in the Development of Multi-Sided Platforms: The Digital Ecosystem Strategy of Alibaba.com

Multi-sided platforms (MSP) are revolutionizing the global competitive landscape in the new networked economy. Yet, although these MSPs are underpinned by information systems (IS), there is currently little research on how the IS capabilities of the platform sponsor can influence, and co-evolve with, the development of the platform over time. The lack of knowledge in this area may account for the difficulties faced by a significant number of platform sponsors in developing their MSPs effectively. Using a case study of Alibaba.com, one of the world’s largest and most commercially successful online MSP, we inductively derive a process theory of MSP development from an IS capability perspective to address this knowledge gap. The process model reveals that the role of IS capabilities in MSP development is evolutionary in nature, and the antecedent IS capabilities, nature, and outcomes of MSP development can be dramatically different in the various stages of development

Zigzag graphene nanoribbons without inversion symmetry

Graphene on a substrate will suffer an inversion-symmetry-breaking (ISB) lattice potential. Taking electron-electron interaction into account, we study in this paper the possibility of half-metallicity and noncollinear (NC) magnetic phase for graphene zigzag nanoribbons without inversion symmetry. At half-filling it is found that half-metallic(HM) state can be achieved at an intermediate value of the ISB potential due to its competition with the electron-electron interaction. Away from half-filling, the phase diagrams of doping versus ISB potential for different ribbon width are given, where the regimes for the HM states and NC magnetic state are clearly indicated and discussed. For ribbons with perfect edges, we predict a topological transition between two HM states with different magnetic structures, which is accompanied by an abrupt transition of electrical conductance along the ribbon from $2e^2/h$ to $e^2/h$.Comment: 7 pages, 7 figure

Modeling the nonperturbative contributions to the complex heavy-quark potential

In this paper, we construct a simple model for the complex heavy quark potential which is defined through the Fourier transform of the static gluon propagator. Besides the hard thermal loop resummed contribution, the gluon propagator also includes a nonperturbative term induced by the dimension two gluon condensate. Within the framework of thermal field theory, the real and imaginary parts of the heavy quark potential are determined in a consistent way without resorting to any extra assumption as long as the exact form of the retarded/advanced gluon propagator is specified. The resulting potential model has the desired asymptotic behaviors and reproduces the data from lattice simulation reasonably well. By presenting a direct comparison with other complex potential models on the market, we find the one proposed in this work shows a significant improvement on the description of the lattice results, especially for the imaginary part of the potential, in a temperature region relevant to quarkonium studiesThis work is supported by the NSFC of China under Project No. 11665008, by Natural Science Foundation of Guangxi Province of China under Projects No. 2016GXNSFFA 380014, No. 2018GXNSFAA138163 and by the Hundred Talents Plan of Guangxi Province of China. The research of M.M. was supported by the European Research Council Grant No. HotLHC ERC-2011-StG-279579S