First-Order Insulator-to-Metal Mott Transition in the Paramagnetic 3D System GaTa4Se8

The nature of the Mott transition in the absence of any symmetry braking remains a matter of debate. We study the correlation-driven insulator-to-metal transition in the prototypical 3D Mott system GaTa4Se8, as a function of temperature and applied pressure. We report novel experiments on single crystals, which demonstrate that the transition is of first order and follows from the coexistence of two states, one insulating and one metallic, that we toggle with a small bias current. We provide support for our findings by contrasting the experimental data with calculations that combine local density approximation with dynamical mean-field theory, which are in very good agreement.Comment: 5 pages and 4 figures. Supplemental material: 2 pages, 2 figure

Scanning tunneling spectroscopy of layers of superconducting 2H-TaSe2_\textbf{2}: Evidence for a zero bias anomaly in single layers

We report a characterization of surfaces of the dichalcogenide TaSe$_2$ using scanning tunneling microscopy and spectroscopy (STM/S) at 150 mK. When the top layer has the 2H structure and the layer immediately below the 1T structure, we find a singular spatial dependence of the tunneling conductance below 1 K, changing from a zero bias peak on top of Se atoms to a gap in between Se atoms. The zero bias peak is additionally modulated by the commensurate $3a_0 \times 3a_0$ charge density wave of 2H-TaSe$_2$. Multilayers of 2H-TaSe$_2$ show a spatially homogeneous superconducting gap with a critical temperature also of 1 K. We discuss possible origins for the peculiar tunneling conductance in single layers.Comment: 10 pages, 10 figure

Domain size effects on the dynamics of a charge density wave in 1T-TaS2

Recent experiments have shown that the high temperature incommensurate (I) charge density wave (CDW) phase of 1T-TaS2 can be photoinduced from the lower temperature, nearly commensurate (NC) CDW state. Here we report a time-resolved x-ray diffraction study of the growth process of the photoinduced I-CDW domains. The layered nature of the material results in a marked anisotropy in the size of the photoinduced domains of the I-phase. These are found to grow self-similarly, their shape remaining unchanged throughout the growth process. The photoinduced dynamics of the newly formed I-CDW phase was probed at various stages of the growth process using a double pump scheme, where a first pump creates I-CDW domains and a second pump excites the newly formed I-CDW state. We observe larger magnitudes of the coherently excited I-CDW amplitude mode in smaller domains, which suggests that the incommensurate lattice distortion is less stable for smaller domain sizes.Comment: 8 pages, 8 figure

Strong enhancement of superconductivity at high pressures within the charge-density-wave states of 2H-TaS 2 and 2H-TaSe 2

We present measurements of the superconducting and charge density wave critical temperatures (Tc and TCDW) as a function of pressure in the transition metal dichalchogenides 2H-TaSe2 and 2H-TaS2. Resistance and susceptibility measurements show that Tc increases from temperatures below 1 K up to 8.5 K at 9.5 GPa in 2H-TaS2 and 8.2 K at 23 GPa in 2H-TaSe2. We observe a kink in the pressure dependence of TCDW at about 4 GPa that we attribute to the lock-in transition from incommensurate CDW to commensurate CDW. Above this pressure, the commensurate TCDW slowly decreases coexisting with superconductivity within our full pressure range.Comment: Published in Phys. Rev B 93, 184512 (2016

Watching the birth of a charge density wave order: diffraction study on nanometer-and picosecond-scales

Femtosecond time-resolved X-ray diffraction is used to study a photo-induced phase transition between two charge density wave (CDW) states in 1T-TaS$_2$, namely the nearly commensurate (NC) and the incommensurate (I) CDW states. Structural modulations associated with the NC-CDW order are found to disappear within 400 fs. The photo-induced I-CDW phase then develops through a nucleation/growth process which ends 100 ps after laser excitation. We demonstrate that the newly formed I-CDW phase is fragmented into several nanometric domains that are growing through a coarsening process. The coarsening dynamics is found to follow the universal Lifshitz-Allen-Cahn growth law, which describes the ordering kinetics in systems exhibiting a non-conservative order parameter.Comment: 6 pages, 5 figure

Differential diagnosis between Marfan syndrome and Loeys–Dietz syndrome type 4: A novel chromosomal deletion covering tgfb2

Marfan syndrome (MFS) and Loeys–Dietz syndrome type 4 (LDS4) are two hereditary connective tissue disorders. MFS displays ectopia lentis as a distinguishing, characterising feature, and thoracic aortic ectasia, aneurysm, dissection, and systemic features as manifestations overlapping with LDS4. LDS4 is characterised by the presence of hypertelorism, cleft palate and/or bifid uvula, with possible ectasia or aneurysms in other arteries. The variable age of onset of clinical manifestations makes clinical diagnosis more difficult. In this study, we report the case of a patient with Marfan syndrome diagnosed at our centre at the age of 33 on the basis of typical clinical manifestations of this syndrome. At the age of 38, the appearance of ectasia of the left common iliac artery and tortuosity of the iliac arteries suggested the presence of LDS4. Next Generation Sequencing (NGS) analysis, followed by Array-CGH, allowed the detection of a novel chromosomal deletion including the entire TGFB2 gene, confirming not only the clinical suspicion of LDS4, but also the clinical phenotype associated with the haploinsufficiency mechanism, which is, in turn, associated with the deletion of the entire gene. The same mutation was detected in the two young sons. This emblematic case confirms that we must be very careful in the differential diagnosis of these two pathologies, especially before the age of 40, and that, in young subjects suspected to be affected by MFS in particular, we must verify the diagnosis, extending genetic analysis, when necessary, to the search for chromosomal alterations. Recently, ectopia lentis has been reported in a patient with LDS4, confirming the tight overlap between the two syndromes. An accurate revision of the clinical parameters both characterising and overlapping the two pathologies is highly desirable

Measuring the State of Disaster Philanthropy 2016: Data to Drive Decisions

This is the third edition of the annual publication Measuring the State of Disaster Philanthropy: Data to Drive Decisions. This report analyzes funding for disasters and humanitarian crises in 2014, the most recent year for which comprehensive data are available. The report examines funding from U.S. foundations, bilateral and multilateral donors, corporations, and smaller donors who give through online platforms

Post-modernism's use and abuse of Nietzsche

I focus on Nietzsche's architectural metaphor of self-construction in arguing for the claim that postmodern readings of Nietzsche misunderstand his various attacks on dogmatic philosophy as paving the way for acceptance of a self characterized by fundamental disunity. Nietzsche's attack on essentialist dogmatic metaphysics is a call to engage in a purposive self-creation under a unifying will, a will that possesses the strength to reinterpret history as a pathway to "the problem that we are". Nietzsche agrees with the postmodernists that unity is not a pre-given, however he would disavow their rejection of unity as a goal. Where the postmodernists celebrate "the death of the subject" Nietzsche rejects this valorization of disunity as a form of Nihilism and prescribes the creation of a genuine unified subjectivity to those few capable of such a goal. Postmodernists are nearer Nietzsche's idea of the Last Man than his idea of the Overman.Articl

Measuring the State of Disaster Philanthropy 2017: Data to Drive Decisions

Each year, the Center for Disaster Philanthropy and Foundation Center analyze global disaster-related funding from foundations, bilateral and multilateral donors, the U.S. Federal Emergency Management Agency (FEMA), corporations, and smaller donors who give through donor advised funds and online platforms. We analyze this funding according to a taxonomy that classifies giving by type of disaster and disaster assistance strategy.Philanthropic funding for disasters and humanitarian crises is situated within a large ecosystem of global aid. While assistance from governments far surpasses funding from foundations, institutional philanthropy still plays an important role. For example, foundations can choose to fill funding gaps and support underfunded areas of the disaster lifecycle. Support for disaster risk reduction and preparedness can mitigate the impact of disasters, and many communities need sustained funding for the long road to recovery. We hope this analysis will aid donors in considering how to maximize the impact of their disaster-related giving

Measuring the State of Disaster Philanthropy 2015: Data to Drive Decisions

Jointly produced by Foundation Center and the Center for Disaster Philanthropy, Measuring the State of Disaster Philanthropy 2015: Data to Drive Decisions analyzes funding trends for disasters and humanitarian crises in 2013. In addition to examining U.S. foundation funding, this second annual report integrates other disaster-related funding data, including bilateral and multilateral aid, corporate giving, and online giving, to paint a more detailed picture of how institutional philanthropy is situated within the broader disaster funding landscape. Collectively, this report, along with the dashboard and mapping platform, provides donors, practitioners, and other stakeholders with in-depth information on funding flows for disasters and humanitarian crises. Explore more at disasterphilanthropy.org