Robert Joseph Cava

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Helical Dirac fermions-charge carriers that behave as massless relativistic particles with an intrinsic angular momentum (spin) locked to its translational momentum-are proposed to be the key to realizing fundamentally new phenomena in condensed matter physics. Prominent examples include the anomalous quantization of magneto-electric coupling, half-fermion(More)
When electrons are subject to a large external magnetic field, the conventional charge quantum Hall effect dictates that an electronic excitation gap is generated in the sample bulk, but metallic conduction is permitted at the boundary. Recent theoretical models suggest that certain bulk insulators with large spin-orbit interactions may also naturally(More)
Bi2Se3 is one of a handful of known topological insulators. Here we show that copper intercalation in the van der Waals gaps between the Bi2Se3 layers, yielding an electron concentration of approximately 2x10{20} cm{-3}, results in superconductivity at 3.8 K in CuxBi2Se3 for 0.12<or=x<or=0.15. This demonstrates that Cooper pairing is possible in Bi2Se3 at(More)
Dirac and Weyl semimetals are 3D analogues of graphene in which crystalline symmetry protects the nodes against gap formation. Na3Bi and Cd3As2 were predicted to be Dirac semimetals, and recently confirmed to be so by photoemission experiments. Several novel transport properties in a magnetic field have been proposed for Dirac semimetals. Here, we report a(More)
Topological insulators are a new class of insulators in which a bulk gap for electronic excitations is generated because of the strong spin-orbit coupling inherent to these systems. These materials are distinguished from ordinary insulators by the presence of gapless metallic surface states, resembling chiral edge modes in quantum Hall systems, but with(More)
We report the direct observation of the three-dimensional (3D) Dirac semimetal phase in cadmium arsenide (Cd(3)As(2)) by means of angle-resolved photoemission spectroscopy. We identify two momentum regions where electronic states that strongly disperse in all directions form narrow conelike structures, and thus prove the existence of the long sought 3D(More)
Magnetoresistance is the change in a material's electrical resistance in response to an applied magnetic field. Materials with large magnetoresistance have found use as magnetic sensors, in magnetic memory, and in hard drives at room temperature, and their rarity has motivated many fundamental studies in materials physics at low temperatures. Here we report(More)
We report an infrared study on 1T-TiSe(2), the parent compound of the newly discovered superconductor Cu(x)TiSe(2). Previous studies of this compound have not conclusively resolved whether it is a semimetal or a semiconductor-information that is important in determining the origin of its unconventional charge density wave (CDW) transition. Here we present(More)
The structural misfit compound PbSe 1.16 TiSe2 2 is reported. It is a superconductor with a Tc of 2.3 K. PbSe 1.16 TiSe2 2 derives from a parent compound, TiSe2, which shows a charge-density wave transition and no superconductivity. The crystal structure, characterized by high-resolution electron microscopy and powder x-ray diffraction, consists of two(More)
We report a study of the low temperature bulk magnetic properties of the spin ice compound Dy2Ti2O7 with particular attention to the (T,4 K) spin freezing transition. While this transition is superficially similar to that in a spin glass, there are important qualitative differences from spin glass behavior: the freezing temperature increases slightly with(More)