Microscopic linear response theory of spin relaxation and relativistic transport phenomena in graphene

We present a unified theoretical framework for the study of spin dynamics and relativistic transport phenomena in disordered two-dimensional Dirac systems with pseudospin-spin coupling. The formalism is applied to the paradigmatic case of graphene with uniform Bychkov-Rashba interaction and shown to capture spin relaxation processes and associated charge-to-spin interconversion phenomena in response to generic external perturbations, including spin density fluctuations and electric fields. A controlled diagrammatic evaluation of the generalized spin susceptibility in the diffusive regime of weak spin-orbit interaction allows us to show that the spin and momentum lifetimes satisfy the standard Dyakonov-Perel relation for both weak (Gaussian) and resonant (unitary) nonmagnetic disorder. Finally, we demonstrate that the spin relaxation rate can be derived in the zero-frequency limit by exploiting the SU(2) covariant conservation laws for the spin observables. Our results set the stage for a fully quantum-mechanical description of spin relaxation in both pristine graphene samples with weak spin-orbit fields and in graphene heterostructures with enhanced spin-orbital effects currently attracting much attention

Optimal Charge-to-Spin Conversion in Graphene on Transition-Metal Dichalcogenides

When graphene is placed on a monolayer of semiconducting transition metal dichalcogenide (TMD) its band structure develops rich spin textures due to proximity spin-orbital effects with interfacial breaking of inversion symmetry. In this work, we show that the characteristic spin winding of low-energy states in graphene on a TMD monolayer enables current-driven spin polarization, a phenomenon known as the inverse spin galvanic effect (ISGE). By introducing a proper figure of merit, we quantify the efficiency of charge-to-spin conversion and show it is close to unity when the Fermi level approaches the spin minority band. Remarkably, at high electronic density, even though subbands with opposite spin helicities are occupied, the efficiency decays only algebraically. The giant ISGE predicted for graphene on TMD monolayers is robust against disorder and remains large at room temperature

Covariant Conservation Laws and the Spin Hall Effect in Dirac-Rashba Systems

We present a theoretical analysis of two-dimensional Dirac-Rashba systems in the presence of disorder and external perturbations. We unveil a set of exact symmetry relations (Ward identities) that impose strong constraints on the spin dynamics of Dirac fermions subject to proximity-induced interactions. This allows us to demonstrate that an arbitrary dilute concentration of scalar impurities results in the total suppression of nonequilibrium spin Hall currents when only Rashba spin-orbit coupling is present. Remarkably, a finite spin Hall conductivity is restored when the minimal Dirac-Rashba model is supplemented with a spin–valley interaction. The Ward identities provide a systematic way to predict the emergence of the spin Hall effect in a wider class of Dirac-Rashba systems of experimental relevance and represent an important benchmark for testing the validity of numerical methodologies

The importance of microenvironment: the role of CCL8 in metastasis formation of melanoma

We have attempted to characterize the changes occurring on the host side during the progression of human melanoma. To investigate the role of tumor microenvironment, we set up such an animal model, which was able to isolate the host related factors playing central role in metastasis formation. One of these 'factors', CCL12, was consequently selected and its behavior was examined alongside its human homologue (CCL8). In our animal model, metastasis forming primary melanoma in the host exhibited increased level of CCL12 mRNA expression. In clinical samples, when examining the tumor and the host together, the cumulative (tumor and host) CCL8 expression was lower in the group in which human primary melanoma formed lung metastasis compared to non-metastatic primary tumors. We could not detect significant difference in CCL8 receptor (CCR1) expression between the two groups. Increased migration of the examined tumor cell lines was observed when CCL8 was applied as a chemoattractant. The tumor cells and their interactions can be influenced the expression of CCL8 by dermal fibroblasts, as a significant change in the metastatic microenvironment. Furthermore, we examined changes in miRNA profile resulted by CCL8 and miR146a appears to be a promising prognostic marker for following this process

Pneumocystis carinii pneumonia in patients with malignant haematological diseases: 10 years' experience of infection in GIMEMA centres.

A retrospective survey was conducted over a 10-year period (1990-99) among 52 haematology divisions in order to evaluate the clinical and laboratory characteristics and outcome of patients with proven Pneumocystis carinii pneumonia (PCP) complicating haematological diseases. The study included 55 patients (18 with non-Hodgkin's lymphoma, 10 with acute lymphoblastic leukaemia, eight with acute myeloid leukaemia, five with chronic myeloid leukaemia, four with chronic lymphocytic leukaemia, four with multiple myeloma, three with myelodys-plastic syndrome, two with myelofibrosis and one with thalassemia) who developed PCP. Among these, 18 (33%) underwent stem cell transplantation; only two received an oral prophylaxis with trimethroprim/sulphamethoxazole. Twelve patients (22%) developed PCP despite protective isolation in a laminar airflow room. The most frequent symptoms were: fever (86%), dyspnoea (78%), non-productive cough (71%), thoracic pain (14%) and chills (5%); a severe hypoxaemia was present in 39 patients (71%). Chest radiography or computerized tomography showed interstitial infiltrates in 34 patients (62%), alveolar infiltrates in 12 patients (22%), and alveolar-interstitial infiltrates in nine patients (16%). Bronchoalveolar lavage was diagnostic in 47/48 patients, induced sputum in 9/18 patients and lung biopsy in 3/8 patients. The diagnosis was made in two patients at autopsy. All patients except one started a specific treatment (52 patients trimethroprim/sulphamethoxazole, one pentamidine and one dapsone). Sixteen patients (29%) died of PCP within 30 d of diagnosis. Multivariate analysis showed that prolonged steroid treatment (P < 0.006) and a radiological picture of diffuse lung involvement (P < 0.003) were negative diagnostic factors

Triplet vs doublet lenalidomide-containing regimens for the treatment of elderly patients with newly diagnosed multiple myeloma

Lenalidomide-dexamethasone improved outcome in newly diagnosed elderly multiple myeloma patients. We randomly assigned 662 patients who were age \u202165 years or transplantation-ineligible to receive induction with melphalan-prednisone-lenalidomide (MPR) or cyclophosphamide-prednisone-lenalidomide (CPR) or lenalidomide plus lowdose dexamethasone (Rd). The primary end point was progression-free survival (PFS) in triplet (MPR and CPR) vs doublet (Rd) lenalidomide-containing regimens. After a median follow-up of 39 months, the medianPFSwas22 months for the triplet combinations and 21 months for the doublet (P 5 .284). The median overall survival (OS) was not reached in either arms, and the 4-year OS was 67% for the triplet and 58% for the doublet arms (P 5 .709). By considering the 3 treatment arms separately, no difference in outcome was detected among MPR, CPR, and Rd. The most common grade \u20213 toxicity was neutropenia: 64% in MPR, 29% in CPR, and 25% in Rd patients (P < .0001). Grade \u20213 nonhematologic toxicities were similar among arms and were mainly infections (6.5% to 11%), constitutional (3.5% to 9.5%), and cardiac (4.5% to 6%), with no difference among the arms. In conclusion, in the overall population, the alkylator-containing tripletsMPRandCPRwere not superior to the alkylator-free doublet Rd, which was associated with lower toxicit

Coupled Charge-Spin Transport and Spin–Orbit Phenomena in 2D Dirac Materials

The advent of 2D layered materials, boasting high-crystal quality and rich electronic properties, has provided a unique arena for exploring exotic condensed-matter phenomena, including the emergence of ultra-relativistic Dirac fermions in graphene, topological insulating phases in WS_{2}, long-lived excitons in group-VI dichalcogenides and unconventional superconductivity in twisted bilayer graphene. The enhancement of spin-orbit effects in heterointerfaces, built from the vertical stacking of different 2D layers, is recently attracting much attention. A series of crucial experiments have demonstrated the induction of strong spin-orbit effects in graphene sheets proximity-coupled to group-VI dichalcogenides. Owing to a combination of room-temperature spin transport over long distances and gate-tunable spin orbit interactions, such systems hold great promise for all-electrical generation and manipulation of spin currents, which is key to the realisation of the next generation of spintronics devices. To fully unlock the potential of 2D Dirac materials for spintronics, these recent experimental findings call for the formulation of a solid theoretical framework which can underpin them, but also—and more importantly—predict novel phenomena. This thesis aims to develop the foundations of such a framework, with a focus on spin dynamics and coupled charge-spin transport in 2D Dirac materials with strong proximity-induced interactions. A number of key results are established. We show that charge-to-spin interconversion in 2D Dirac materials can be understood in terms of exact symmetry relations (Ward identities). Depending on the specific spin-orbit interactions present in a 2D Dirac system, the symmetry relations dictate the relative contributions of the so-called spin-Hall effect (SHE) and inverse spin Galvanic effect (ISGE). In particular, for materials with interfacial breaking of mirror symmetry and unbroken (broken) sublattice symmetry, the SHE contribution is suppressed (sizable), whereas the ISGE contribution stays typically large and robust in both scenarios. The extrinsic SHE has its origin in a peculiar skew scattering mechanism—emerging from the non-coplanar spin texture of spin–orbit-coupled Dirac bands—and can be tuned by a gate voltage. We propose a diagrammatic approach to obtain the coupled charge/spin diffusion equations, as well as the spin relaxation times and the charge-to-spin interconversion rates. We supplement this study with a density matrix-based approach, allowing one to gain more insight into the delicate competition of the various energy scales present in realistic systems, and to calculate the spin relaxation time anisotropy of experimental relevance. Finally, we examine ferromagnetic 2D Dirac materials, through a unified theory of charge carrier transport combining semiclassical and fully-quantum mechanical approaches. We identify an experimental signature that characterises the crossover from the nonquantised anomalous Hall effect to the topologically-nontrivial quantum anomalous Hall effect, which can help future experimental efforts to unlock this fascinating quantum state of matter with Dirac fermions