Spin and charge optical conductivities in spin-orbit coupled systems

We study the frequency dependent spin- and charge- conductivity tensors of a two-dimensional electron gas (2DEG) with Rashba and Dresselhaus spin-orbit interaction. We show that the angular anisotropy of the spin-splitting energy induced by the interplay between the Rashba and Dresselhaus couplings gives rise to a characteristic spectral behavior of the spin and charge response which is significantly different from that of pure Rashba or Dresselhaus case. Such new spectral structures open the possibility for control of the optical response by applying an external bias and/or by adjusting the light frequency. In addition, it is shown that the relative strength of the spin-orbit coupling parameters can be obtained through optical probing.Comment: 13 pages, 4 figures. Revised versio

Prioritising project management competences across the software project life cycle

Purpose The purpose of this paper is to investigate the relative importance of project management (PM) competences across the different stages of a software project life cycle to identify competence development gaps and opportunities. Design/methodology/approach A deductive and quantitative approach was adopted to address the research questions with a web-based survey for data collection. Findings After reviewing the context of competences and PM competences, the importance of the PM competences overall and for specific stages in the project life cycle was analysed. The result highlights that functional and meta-competences are perceived to be the most important competence dimensions for software project practitioners. Originality/value This study makes three contributions. First, it consolidates PM competences into a set of 20 within four competence dimensions. Second, it prioritises these competences across the software project life cycle. Third, it identifies the significance of the inter-relationship between PM competences and project life cycle to reveal PM competence development gaps and opportunities

Spin torque contribution to the a.c. spin Hall conductivity

Using the recently proposed definition of a conserved spin-current operator [J. Shi et al., Phys. Rev. Lett. 96, 076604 (2006)] we explore the frequency dependent spin Hall conductivity for a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit interaction in response to an oscillating electric field. We show that the optical spectrum of the spin Hall conductivity exhibit remarkable changes when the new definition of spin current is applied. Such behavior is mainly due to a significant contribution of the spin torque term which is absent in the conventional form of the spin current. In addition, it is observed that the magnitude and direction of the dynamic spin Hall current strongly depends on the electric field frequency as with the interplay of the spin-orbit coupling strengths.Comment: 8 pages, 4 figures, pape

Charge and spin density response functions of the clean two-dimensional electron gas with Rashba spin-orbit coupling at finite momenta and frequencies

We analytically evaluate charge and spin density response functions of the clean two-dimensional electron gas with Rashba spin-orbit coupling at finite momenta and frequencies. On the basis of our exact expressions we discuss the accuracy of the long-wavelength and the quasiclassical approximations. We also derive the static limit of spin susceptibilities and demonstrate, in particular, how the Kohn-like anomalies in their derivatives are related to the spin-orbit modification of the Ruderman-Kittel-Kasuya-Yosida interaction. Taking into account screening and exchange effects of the Coulomb interaction, we describe the collective charge and spin density excitation modes which appear to be coupled due to nonvanishing spin-charge response function.Comment: 15 pages, 9 figure

Interplay of the Rashba and Dresselhaus spin-orbit coupling in the optical spin susceptibility of 2D electron systems

We present calculations of the frequency-dependent spin susceptibility tensor of a two-dimensional electron gas with competing Rashba and Dresselhaus spin-orbit interaction. It is shown that the interplay between both types of spin-orbit coupling gives rise to an anisotropic spectral behavior of the spin density response function which is significantly different from that of vanishing Rashba or Dresselhaus case. Strong resonances are developed in the spin susceptibility as a consequence of the angular anisotropy of the energy spin-splitting. This characteristic optical modulable response may be useful to experimentally probe spin accumulation and spin density currents in such systems

Prioritising project management competences across the software project life cycle

This paper investigates the relative importance of project management competences across the different stages of a software project life cycle to identify competence development gaps and opportunities.A deductive and quantitative approach was adopted to address our research questions with a web-based survey for data collection.After reviewing the context of competences and project management competences, the importance of the project management competences overall and for specific stages in the project life cycle was analysed. The result highlights that functional and meta-competences are perceived to be the most important competence dimensions for software project practitioners.This study makes three contributions. First, it consolidates PM competences into a set of 20 within four competence dimensions. Second, it prioritises these competences across the software project life cycle. Third, it identifies the significance of the inter-relationship between project management competences and project life cycle to reveal project management competence development gaps and opportunities.<br/

Generalized rotating-wave approximation for the quantum Rabi model with optomechanical interaction

We investigate the spectrum of energy and eigenstates of a hybrid cavity optomechanical system, where a cavity field mode interacts with a mechanical mode of a vibrating end mirror via radiation pressure and with a two level atom via electric dipole interaction. In the spirit of approximations developed for the quantum Rabi model beyond rotating-wave approximation (RWA), we implement the so-called generalized RWA (GRWA) to diagonalize the tripartite Hamiltonian for arbitrary large couplings. Notably, the GRWA approach still allows to rewrite the hybrid Hamiltonian in a bipartite form, like a Rabi model with dressed atom-field states (polaritons) coupled to mechanical modes through reparametrized coupling strenght and Rabi frequency. We found a more accurate energy spectrum for a wide range of values of the atom-photon and photon-phonon couplings, when compared to the RWA results. The fidelity between the numerical eigenstates and its approximated counterparts is also calculated. The degree of polariton-phonon entanglement of the eigenstates presents a non-monotonic behavior as the atom-photon coupling varies, in contrast to the characteristic monotonic increase in the RWA treatment

Linear and nonlinear spin current response in anisotropic spin-orbit coupled systems

We calculate the linear and the second harmonic (SH) spin current response of two anisotropic systems with spin orbit (SO) interaction. The first system is a two-dimensional (2D) electron gas in the presence of Rashba and k-linear Dresselhaus SO couplings. The dependence of the anisotropic spin splitting on the sample growth direction introduces an additional path to modify the linear and nonlinear spectra. In particular, vanishing linear and second order spin conductivity tensors are achievable under SU(2) symmetry conditions, characterized by a collinear SO vector field. Additional conditions under which specific tensor components vanish are posible, without having such collinearity. Thus, a proper choice of the growth direction and SO strengths allows to select the polarization of the linear and SH spin currents according to the direction of flowing. The second system is an anisotropic 2D free electron gas with anisotropic Rashba interaction, which has been employed to study the optical conductivity of 2D puckered structures with anisotropic energy bands. The presence of mass anisotropy and an energy gap open several distinct scenarios for the allowed optical interband transitions, which manifest in the linear and SH response contrastingly. The linear response displays only out-of-plane spin polarized currents, while the SH spin currents flow with spin orientation lying parallel to the plane of the system strictly. The models illustrate the possibility of the nonlinear spin Hall effect in systems with SO interaction, under the presence or absence of time-reversal symmetry. The results suggest different ways to manipulate the linea

Strategic Project Organizing

Strategic Project Organizing takes a unique approach to project management that places emphasis on the strategic and organizational aspects of projects and their leadership. Structured around the Three Domains model, it covers all the fundamental project management concepts, whilst guiding the reader through the organizational challenges of enabling positive change. Through the lens of strategic leadership, this text equips students to know how to respond proactively to threats, as well as seize opportunities, in order to advantageously change the socio-economic environment in an organization's favour. The text also helps students to understand the tools and techniques adopted during the process of organizational transformation. All chapters offer review and discussion-based questions to encourage critical thinking; as well as case vignettes and a longer, end-of-chapter case study to help students apply theory to practice. Real life projects featured in the case studies include the Eden Project, the Thames Tideway Tunnel and the Berlin Brandenburg Airport