Visualizing Quantum States of Matter
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One-dimensional Topological Edge States of Bismuth Bilayers
Sunday, August 10, 2014
Bismuth bilayers have been among the first systems theoretically predicted to be a two-dimensional topological insulator. We have been able to study the topological edge modes of bismuth bilayer system by carrying out scanning tunneling spectroscopy measurements on bulk bismuth samples. By performing edge state quasiparticle interference experiment we were able to show the absence of backscattering as well as reveal other intriguing properties emerging from topological properties of bismuth bilayers.

Published in Nature Physics:
One-dimensional Topological Edge States of Bismuth Bilayers, Ilya K. Drozdov, A. Alexandradinata, Sangjun Jeon, Stevan Nadj-Perge, Huiwen Ji, R. J. Cava, B. A. Bernevig, Ali Yazdani, Nature Physics 10, 663-669 (2014). (Article)
Landau Quantization and Quasiparticle Interference in the Three-Dimensional Dirac Semimetal Cd3As2
Sunday, June 29, 2014
A pair of Weyl fermions protected by crystalline symmetry has been proposed to appear as low-energy excitations in a number of materials termed 3D Dirac semimetals. Cd3As2 known to have a high mobility is one of the first candidates to exhibit a bulk 3D Dirac semimetal phase which is protected by the C4 symmetry of the crystalline structure. In recent study, our group has revealed the novel band structure of the Cd3As2 by combining the Landau level spectroscopy and the quasiparticle interference. Our measurements show a remarkable linear dispersion in wide energy range which extended the understanding of ultra-high mobility nature of Cd3As2. In addition to that simulating the model Hamiltonian with parameters which reproduce the experimental data suggests Weyl fermions are the low-energy excitations when a magnetic field applied along the axis of the Dirac points.

Published in Nature Materials:
Landau Quantization and Quasiparticle Interference in the Three-Dimensional Dirac Semimetal Cd3As2, Sangjun Jeon, Brian B. Zhou, Andras Gyenis, Benjamin E. Feldman, Itamar Kimchi, Andrew C. Potter, Quinn D. Gibson, Robert J. Cava, Ashvin Vishwanath, Ali Yazdani, Nature Materials 13, 851-856 (2014). (Letter)