Microscopic simulation of superconductor-topological insulator proximity structures

We present microscopic, self-consistent calculations of the superconducting order parameter and pairing correlations near the interface of an $s$-wave superconductor and a three-dimensional topological insulator with spin-orbit coupling. We discuss the suppression of the order parameter by the topological insulator and show that the equal-time pair correlation functions in the triplet channel, induced by spin-flip scattering at the interface, are of $p_x\pm i p_y$ symmetry. We verify that the spectrum at sub-gap energies is well described by the Fu-Kane model. The sub-gap modes are viewed as interface states with spectral weight penetrating well into the superconductor. We extract the phenomenological parameters of the Fu-Kane model from microscopic calculations, and find they are strongly renormalized from the bulk material parameters. This is consistent with previous results of Stanescu et al for a lattice model using perturbation theory in the tunneling limit.Comment: 8 pages, 10 figures; references added in v

Mott scattering at the interface between a metal and a topological insulator

We compute the spin-active scattering matrix and the local spectrum at the interface between a metal and a three-dimensional topological band insulator. We show that there exists a critical incident angle at which complete (100%) spin flip reflection occurs and the spin rotation angle jumps by $\pi$. We discuss the origin of this phenomena, and systematically study the dependence of spin-flip and spin-conserving scattering amplitudes on the interface transparency and metal Fermi surface parameters. The interface spectrum contains a well-defined Dirac cone in the tunneling limit, and smoothly evolves into a continuum of metal induced gap states for good contacts. We also investigate the complex band structure of Bi$_2$Se$_3$.Comment: published versio

رجال أعمال دمشق: أشباح "ماروتا سيتي"

This paper analyses the Syrian regime’s conception of reconstruction relying on building luxurious tourist and service projects, including transforming the Damascus real estate market into a primary source of revenue by attracting foreign investment. The paper examines the establishment of the Damascus Cham Holding Company to administer the property of the Governorate of Damascus and the main motors driving this project, especially by investigating the financing of the implementation of the ‘Marota’ project. It also explores the company’s partnerships with Syrian businessmen, most of whom were previously unknown. This is a practical example of absolute clientelism in the Syrian economy, as some ‘Marota’ businessmen behave more like business directors for major players in the regime’s inner circle than like representatives of the private sector. The paper concludes that the completion of the Marota project will face numerous challenges, the most important of which is funding. This is especially the case following the imposition of European sanctions on businessmen participating in the project and their partners. The regime will not refrain from using the names of new businessmen to avoid sanctions.تنظر الورقة في مفهوم النظام السوري لإعادة الإعمار المُستنِد إلى إقامة مشاريع سياحية وخدماتية فاخرة، بما يضمن تحويل سوق العقارات في دمشق إلى مولّدٍ رئيسٍ للريع، عبر استقطاب الاستثمارات الخارجية. وتستعرض الورقة تأسيس شركة دمشق الشام القابضة الخاصة لإدارة أملاك محافظة دمشق، والمحرّكات الرئيسة خلف هذا التأسيس، ولا سيّما من جهة البحث عن التمويل لتنفيذ مشروع "ماروتا". كما تستكشف تعاقد الشركة مع رجال أعمالٍ سوريين، معظمهم لم يكن معروفاً سابقاً، في مثالٍ عمليّ على الزبائنية المُفرَطة في الاقتصاد السوري، حيث يتصرّف بعض رجال أعمال "ماروتا" كمدراء أعمالٍ لمتنفّذين كبار في دائرة النظام الضيّقة، أكثر ممّا يتصّرفون كممثّلين للقطاع الخاص. تخلُص الورقة أخيراً إلى أن إنجاز مشروع "ماروتا" ستحول دونه عقبات عدّة أهمّها التمويل، خصوصاً بعد فرض العقوبات الأوروبية على رجال الأعمال المشاركين فيه وشركاتهم، ولا تستبعد طرح النظام أسماءَ رجال أعمالٍ جددٍ للتحايل على العقوبا

The Druze of Sweida : the return of the Regime Hinges on regional and local conflicts

Since 2011, the Druze of Sweida have witnessed a state of chaos and anxiety, a decline in the role of the middle class and their traditional and political leaders, and serious exposure to regional interference. In early 2019, the Syrian regime resumed its pressure on Sweida’s Druze to join its armed forces amid resistance from some local armed forces, raising the questions of the possibility of the regime directly ruling Sweida through its security and military institutions once again, the conditions in which this would take place and the local factors that might impede it. This paper first examines the factors that changed the ethnic nature of the Druze in terms of the relationship between their local political and religious leaderships and the reasons for the continuity of spiritual leadership and the erosion of its secular counterpart. The paper also maps out the forms of interventions by Iran, Russia and the Druze of Lebanon and Israel and their interrelationships with local forces and impact on the rearrangement of the local social order in Sweida. Finally, the study presents possible future scenarios for the region