Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session K41: Topological Kondo Semimetals and Low Carrier SystemsInvited

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Sponsoring Units: DCMP DMP Chair: Piers Coleman, Rutgers Univ Room: LACC 502A 
Wednesday, March 7, 2018 8:00AM  8:36AM 
K41.00001: Experimental Evidence for Weyl Semimetal Behavior in Kondo Systems Invited Speaker: Silke BuehlerPaschen The quest for topologically nontrivial phases in strongly correlated electron systems has recently led to the notion of WeylKondo semimetals [1]. We have observed direct thermodynamic evidence for the corresponding linear electronic dispersion, with strongly renormalized velocity, in the new noncentrosymmetric cubic material Ce_{3}Bi_{4}Pd_{3} [2]. Its isostructural sister compound Ce_{3}Bi_{4}Pt_{3} is a canonical Kondo insulator. Our study of the substitution series Ce_{3}Bi_{4}(Pt_{1x}Pd_{x})_{3} showed that, while the replacement of the 5d element Pt by the much lighter 4d element Pd strongly reduces the conduction electron spinorbit coupling, it is isostructural, isoelectronic, and isosize [2]. This indicates that the Weyl semimetal state may develop near a (noncentrosymmetric) Kondo insulator in the presence of reduced spinorbit coupling. Also other candidate materials, in particular tetragonal CeRu_{4}Sn_{6} [35] and orthorhombic CeNiSn [6], will be discussed. 
Wednesday, March 7, 2018 8:36AM  9:12AM 
K41.00002: WeylKondo Semimetal in Heavy Fermion Systems Invited Speaker: HsinHua Lai The study of strongly correlated and topologically nontrivial insulators goes back in decades to quantum Hall systems. By contrast, topological conductors with strong correlations have yet to be identified. Heavy fermion semimetals are a prototype of strongly correlated systems and, given their inherently strong spinorbit coupling, present a natural setting to make progress. We have advanced a WeylKondo semimetal phase [1] within a welldefined threedimensional lattice model that breaks the inversion symmetry. The quasiparticles near the Weyl nodes develop out of the Kondo effect, as do the surface states that feature Fermi arcs. This has allowed us to propose a key thermodynamic signature of the WeylKondo semimetal phase, viz. the specific heat C going as T cubed with a prefactor enhanced by as much as 9 orders of magnitude compared to the expected value for weakly correlated systems. This thermodynamic signature has been realized in the recently discovered heavy fermion semimetal Ce_{3}Bi_{4}Pd_{3} [2]. Our findings provide the muchneeded theoretical foundation for the experimental search of topological conductors with strong correlations, and open up a way for systematic studies of such quantum phases that naturally entangle multiple degrees of freedom. 
Wednesday, March 7, 2018 9:12AM  9:48AM 
K41.00003: Evidence for topological Kondo semimetals Invited Speaker: Chunyu Guo , Fan Wu , Michael Smidman , Yang Liu , Chao Cao , Frank Steglich , Huiqiu Yuan In this presentation, we will report our recent progress studying the topological properties of the correlated semimetals RX (R = Ce, Pr, Sm; X=Sb, Bi) and YbPtBi. 
Wednesday, March 7, 2018 9:48AM  10:24AM 
K41.00004: New aspects in topological heavy fermion systems Invited Speaker: PoYao Chang , Piers Coleman , Onur Erten Heavy fermion materials provide a playground to extend our current understanding of topological phases of matter. This talk will present two new types of topological Kondo systems that go beyond the standard models. Firstly, when topology meets nonsymmorphic crystal symmetries, a Z4 topological insulating phase emerges with Mobius twisted surface states. The heavy fermion semimetal CeNiSn is one candidate ”Mobius Kondo Insulators”[1]. Secondly, heavy Weyl semimetals can emerge from topological Kondo insulators drive by the formation of a parityviolating hybridization between d and felectrons [2]. We show the renormalization effect induced by hybridization and the development of the surface Kondo breakdown, which gives rise to a temperaturedependent of reconfiguration of Fermi arcs which will be visible in quantum oscillation experiments.

Wednesday, March 7, 2018 10:24AM  11:00AM 
K41.00005: ARPES investigations of proposed topological low carrier density Ce and Yb compounds Invited Speaker: Jonathan Denlinger In the search for new strongly correlated topological materials, going beyond the initial candidate material SmB_{6}, a number of issues arise in the angleresolved photoemission (ARPES) interpretations of observed Diraclike band dispersions and twodimensionality. In particular the example of YbB_{6}, a divalent smallgap semiconductor at ambient pressure, misinterpreted as a topological Kondo insulator, highlights issues of surface termination, polarity and bandbending, Vshaped nonparabolicity of band dispersions arising from small gaps, degrees of twodimensionality, interpretation of circular dichroism, and use of theoretical bandgap correction methods. With such lessons in mind, we focus attention on three low carrier density heavy fermion systems of (i) YbPtBi, an ultraheavyfermion halfHeusler semimetal, (ii) CeSb and related fcc monopnictide semimetals, and (iii) CeRhSb, a Kondo insulator with predicted Mobiustype surface state dispersion. We critically assess the ARPES evidence for their proposed topological properties and highlight the tool of surface alkalidosing to help distinguish surface state scenarios. In addition, we report progress in the understanding of their various bulk properties including CEF splittings, temperaturedependence of fstates and magnetic ground states. 
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