Annual meeting of the Swiss Physical Society 2018

Session

Advances in Topological Materials

30 Aug 2018, 14:00

CE 2 (EPFL)

14. 【601】 Topology-driven thermoelectricity and non-abelian statistics in momentum space

Alexey Soluyanov (ETH Zurich)

30/08/2018, 14:00

Advances in Topological Materials

Talk

I will present examples of metals, which have topologically protected crossings in the phonon spectrum. I will show how the topological invariant of such crossings is defined and will show that the presence of such crossings puts the hosting metals among the best known thermoelectric metallic compounds.
Apart from that I will introduce the notion of non-abelian topological charge, defined in...

21. 【602】 Observation of Weyl nodes in robust type-II Weyl semimetal WP2

Mengyu Yao (PSI - Paul Scherrer Institut)

30/08/2018, 14:30

Advances in Topological Materials

Talk

Weyl semimetal is a topological nontrivial phase of condensed matter which hosts 2-fold degenerate Weyl nodes formed by unavoidable crossings of linearly dispersive bands. The tilted Weyl cone, Lorentz invariance violation and unusual transport properties distinguish the type-II WSM from its type-I counterpart. By combining ARPES study and first-principles calculations, we present the...

232. 【603】 Topological quantum phases in graphene nanoribbons

Dr Pascal Ruffieux (nanotech@surfaces Laboratory, Empa – Dübendorf, Switzerland)

30/08/2018, 14:45

Advances in Topological Materials

Talk

Topological materials have attracted great interest in solid state physics due to their ability to support robust quantum states at their boundaries. Recently, it has been predicted that localized zero energy modes can be obtained at junctions of topologically dissimilar graphene nanoribbons (GNR). Within a surface-assisted bottom-up approach using rationally designed molecular precursors, we...

132. 【604】 Observation of a phononic quadrupole topological insulator

Dr Marc Serra Garcia (ETH Zurich)

30/08/2018, 15:00

Advances in Topological Materials

Talk

Many topological band structures can be understood as consequences of a quantized Berry phase along phase-space trajectories, which arises from charge polarization. The theory relating topology and polarization has been recently extended to higher-order multipolar moments. Although originally based on the concept of charge polarization, the same theory can also be used to characterize the...

112. 【605】 Axial field induced chiral channels in an acoustic Weyl system

Valerio Peri (ETH Zurich)

30/08/2018, 15:15

Advances in Topological Materials

Talk

Using super-structures one can effectively change the way that sound waves propagates in space. Topological band theory, known from the description of electrons in solids, provides us with a powerful design-principle for such acoustic metamaterials. Weyl points are robust conical band crossings in three dimensional materials that are monopoles of Berry curvature. When a magnetic field is...

109. 【606】 Type-I and type-II classification of composite Weyl nodes

Daniel Gosalbez Martinez (Institute of Physics, Ecole Polytechnique F\'ed\'erale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland)

30/08/2018, 15:30

Advances in Topological Materials

Talk

Linear Weyl nodes are classified in type-I and type-II. The Fermi surface, described by a $2^{nd}$ order algebraic surface, has a well define morphology for each type of Weyl point. When the $C_4$ and $C_6$ rotation symmetries forbid linear energy dispersion, as it happens in the composite Weyl nodes, terms with a quadratic or cubic dispersion must be included into the Hamiltonian....

163. 【607】 Signatures of the 6D Quantum Hall effect in 3D topological pumps

Ioannis Petrides (ETH Zurich)

30/08/2018, 15:45

Advances in Topological Materials

Talk

The 6-dimensional Quantum Hall effect offers rich physics that generalize the concepts developed over decades for its 2-dimensional cousin. Using modern technological advances that allow for the study of systems with additional synthetic dimensions, higher-dimensional physics that was previously deemed to be of purely theoretical interest can now be accessed. In this talk, I will show how a...

62. 【608】 Non-trivial band topology in high pressure structure of Ba$_3$CaIr$_2$O$_9$

Vamshi Mohan Katukuri (EPFL)

30/08/2018, 16:00

Advances in Topological Materials

Talk

Iridium oxides with $d^5$ configuration have attracted considerable interest in the last decade due to the realisation of spin-orbit-coupled (SOC) $j_{eff}=1/2$ insulating ground states. Recently, a new class of 5$d^4$ iridates with a singlet ($j_{eff}=0$) ground states have been realised in (Ba/Sr)$_2$YIrO$_6$. Here, we propose a new honeycomb lattice compound Ba$_3$CaIr$_2$O$_9$ in...

198. 【609】 High-pressure phases of Kitaev Materials

Gediminas Simutis (Paul Scherrer Institute)

30/08/2018, 16:15

Advances in Topological Materials

Talk

Bond-dependent interactions between magnetic moments can lead to strong frustration and nontrivial ground states. In particular, the Kitaev-Heisenberg model has a rich phase diagram and can host a spin liquid state or different frozen states depending on the strength of the additional Heisenberg interactions. Experimentally such phase diagrams can be explored by modifying the relative...

55. 【611】 Emergence of massless Dirac and Weyl fermions in Semi-metals with broken PT symmetry

Prof. Ming Shi (Paul Scherrer Institut)

31/08/2018, 11:15

Advances in Topological Materials

Talk

The Weyl and Dirac semimetals are recently discovered topological quantum states of matter characterized by the unavoidable crossing of two non- or doubly-degenerate energy bands near the Fermi level, respectively. These crossing points (Weyl or Dirac nodes) are the source of exotic phenomena, including the realization of massless Dirac and Weyl fermions as quasiparticles in the bulk and the...

121. 【612】 Novel topological semimetals predicted from first-principles

Quansheng Wu (EPFL - EPF Lausanne)

31/08/2018, 11:45

Advances in Topological Materials

Talk

The theoretical prediction and experimental validation of Na3Bi and Cd3As2 Dirac semimetals, as well as the TaAs-class Weyl semimetals, stimulated considerable research efforts aiming at extending the family of topological semimetals. Several new classes of gapless topological phases such as the topological nodal-line, nodal-chain, and nodal-net systems as well as high-dimensional fermions...

39. 【613】 Reinvestigating the surface and bulk electronic properties of Cd3As2

Dr Alberto Crepaldi (Institute of Physics, Ecole Polytechnique F\'ed\'erale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland)

31/08/2018, 12:00

Advances in Topological Materials

Talk

Cd3As2 is generally considered as archetype of the three-dimensional Dirac semimetal phase, the 3D analogue of graphene with linearly dispersing bulk state. Our reinvestigation of its electronic properties calls for a revision of this simplistic description. Cd3As2 exhibits, in fact, both a surface state and two bulk bands, dispersing across the Fermi level. Hence, these states must all...

85. 【614】 Prediction of a large-gap and switchable Kane-Mele quantum spin Hall insulators from first-principles simulations

Mr Antimo Marrazzo (Theory and Simulation of Materials (THEOS), and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland)

31/08/2018, 12:15

Advances in Topological Materials

Talk

Fundamental research and technological applications of topological insulators are hindered by the rarity of materials exhibiting a robust topologically non-trivial phase, especially in two dimensions. Here, by means of extensive first-principles calculations, we propose a novel quantum spin Hall insulator (QSHI) with a sizeable band gap of ∼0.5 eV that is a monolayer of jacutingaite, a...

66. 【615】 Magnetoresistance from Fermi surface topology

Dr Shengnan Zhang (Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland and National Centre for Computational Design and Discovery of Novel Materials MARVEL, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland)

31/08/2018, 12:30

Advances in Topological Materials

Talk

Magnetoresistance of both topologically trivial and nontrivial materials was extensively studied during past few years. Different mechanisms were proposed to explain the magnetotransport properties, such as the extremely large non-saturating magnetoresistance observed in a number of materials, without arriving to definitive conclusions. By combining of ab initio calculations based on DFT with...

64. 【616】 Electronic and spin structure of the nodal-line semimetals ZrSiX (X=Se,Te)

Gianmarco Gatti (EPFL)

31/08/2018, 12:45

Advances in Topological Materials

Talk

We report a comprehensive study of the low-energy bandstructure of the nodal-line semimetals ZrSiX (X = Se,Te), combining angle-resolved photoemission spectroscopy (ARPES) and first-principle calculations. We discriminate between the existence of bulk and surface states, whose spin texture is revealed by the means of spin-resolved ARPES and confirmed by our calculations. Interestingly, a...

43. 【617】 Experimental evidence of proximity induced odd-frequency superconductivity in a topological insulator

Mr Jonas Krieger (Paul Scherrer Institut)

31/08/2018, 13:00

Advances in Topological Materials

Talk

At an interface between a topological insulator (TI) and a conventional $s$-wave superconductor, the induced superconductivity in the TI surface state is expected to develop a complex $p$-wave order parameter which may allow to create Majorana Fermions inside vortex cores. These collective excitations are the basic element in a proposal for fault-tolerant quantum computing. Here we present...