Crystal Structure and Chemistry of Topological Insulators

Topological surface states, a new kind of electronic state of matter, have recently been observed on the cleaved surfaces of crystals of a handful of small band gap semiconductors. The underlying chemical factors that enable these states are crystal symmetry, the presence of strong spin orbit coupling, and an inversion of the energies of the bulk electronic states that normally contribute to the valence and conduction bands. The goals of this review are to briefly introduce the physics of topological insulators to a chemical audience and to describe the chemistry, defect chemistry, and crystal structures of the compounds in this emergent field.Comment: Submitted to Journal of Materials Chemistry, 47 double spaced pages, 9 figure

Gold-Gold Bonding: The Key to Stabilizing the 19-Electron Ternary Phases LnAuSb (Ln = La-Nd and Sm) as New Dirac Semimetals

We report a new family of ternary 111 hexagonal LnAuSb (Ln = La-Nd, Sm) compounds that, with a 19 valence electron count, has one extra electron compared to all other known LnAuZ compound. The "19th" electron is accommodated by Au-Au bonding between the layers; this Au-Au interaction drives the phases to crystallize in the YPtAs-type structure rather than the more common LiGaGe-type. This is critical, as the YPtAs structure type has the symmetry-allowed band crossing necessary for the formation of Dirac semimetals. Band structure, density of stats, and crystal orbital calculations confirm this picture, which results in a nearly complete band gap between full and empty electronic states and stable compounds; we can thus present a structural stability phase diagram for the LnAuZ (Ln = Ge, As, Sn, Sb, Pb, Bi) family of phases. Those calculations also show that LaAuSb has a bulk Dirac cone below the Fermi level. The YPtAs-type LnAuSb family reported here is an example of the uniqueness of gold chemistry applied to a rigidly closed shell system in an unconventional way.Comment: 32 pages, 8 Figure

Legal-economic Koinè and the Religious Nomopoiesis

In the economic field, the law is often perceived solely for the service function it provides (or should provide) to the benefit of market players. The economy thus drives the creation of negotiating instruments at the service of the great private economic powers. As a result, the weaker "parties" accept negotiating constraints which, although apparently voluntarily assumed in their conclusions and effects, actually limit their freedom by creating a functional and economic dependency. Is there a way to break this link and intervene in defense of values such as equality and solidarity which should be integral to contemporary societies? Among the various possibilities for positive conduct, religions are placed in the front row, above all for their nomopoietic function. Religious values and rights contribute to making the processes of “law systems self-analysis” more just, by curbing the interpretations of the law that benefit the economically dominant social classes

Bi2Te1.6S1.4 - a Topological Insulator in the Tetradymite Family

We describe the crystal growth, crystal structure, and basic electrical properties of Bi2Te1.6S1.4, which incorporates both S and Te in its Tetradymite quintuple layers in the motif -[Te0.8S0.2]-Bi-S-Bi-[Te0.8S0.2]-. This material differs from other Tetradymites studied as topological insulators due to the increased ionic character that arises from its significant S content. Bi2Te1.6S1.4 forms high quality crystals from the melt and is the S-rich limit of the ternary Bi-Te-S {\gamma}-Tetradymite phase at the melting point. The native material is n-type with a low resistivity; Sb substitution, with adjustment of the Te to S ratio, results in a crossover to p-type and resistive behavior at low temperatures. Angle resolved photoemission study shows that topological surface states are present, with the Dirac point more exposed than it is in Bi2Te3 and similar to that seen in Bi2Te2Se. Single crystal structure determination indicates that the S in the outer chalcogen layers is closer to the Bi than the Te, and therefore that the layers supporting the surface states are corrugated on the atomic scale.Comment: To be published in Physical Review B Rapid Communications 16 douuble spaced pages. 4 figures 1 tabl

The denial of religious freedom: a new approach to the system

Text in process of completion, not subject to referee review, of Report at the Conference on "La libertà religiosa nell'età post-secolare" in Lugano, Faculty of Theology (27-28 March 2014).SOMMARIO: 1. Introduction: the social power of religions and the need for dialogue - 2. Law as a required hurdle to the “disclaimers” of religious freedom - 3. The restrictions to the exercise of religious freedom: an overview - 4. Religious freedom and social welfare: an inseparable duo - 5. Brief conclusions

The denial of religious freedom: a new approach to the system

Text in process of completion, not subject to referee review, of Report at the Conference on "La libertà religiosa nell'età post-secolare" in Lugano, Faculty of Theology (27-28 March 2014).SOMMARIO: 1. Introduction: the social power of religions and the need for dialogue - 2. Law as a required hurdle to the “disclaimers” of religious freedom - 3. The restrictions to the exercise of religious freedom: an overview - 4. Religious freedom and social welfare: an inseparable duo - 5. Brief conclusions

Religious freedom and objectives for economic intercultural development

Text, accepted by the Director, of the report presented at the International Consultation on Religious Freedom Research (Istanbul on 17 March 2013), supervised by Prof. Antonio Fuccillo. This text was admitted after being assessed by the members of the evaluation scientific committee of the International Institute of Religious Freedom.SUMMARY: 1. The theory of public goods: religious freedom as a public good – 2. Economics and religion: the reasons for the need of intercultural relationship – 3. Religious factors and asymmetric information in economics – 4. Ethical development, religion and the cross-cultural domain – 5. Financial choices and religious factors – 6. Concluding remarks