Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session D43: Interaction Induced Topological Insulators |
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Sponsoring Units: DCMP Chair: Oliver Rader, The Helmholtz Centre Berlin for Materials and Energy Research Room: Mile High Ballroom 4B |
Monday, March 3, 2014 2:30PM - 2:42PM |
D43.00001: Correlated topological phase in rare earth Hexaboride Nan Xu, X. Shi, P. Biswas, C. Matt, R. Dhaka, Y. Huang, N. Plumb, M. Radovic, J. Dil, E. Pomjakushina, K. Conder, A. Amato, Z. Salman, D. Paul, J. Mesot, Hong Ding, Ming Shi We have performed an angle-resolved photoemission spectroscopy study on SmB6 in order to elucidate elements of the electronic structure relevant to the possible occurrence of a topological Kondo insulator state. Our results reveal one electron-like 5d bulk band centered at the X point of the bulk Brillouin zone that is hybridized with strongly correlated f electrons, as well as the opening of a Kondo band gap ($\sim$20 meV) at low temperature. In addition, we observe electron-like bands forming three Fermi surfaces at the center Gamma-bar point and boundary X-bar point of the surface Brillouin zone. These bands are not expected from calculations of the bulk electronic structure, and their observed dispersion characteristics are consistent with surface states. Our results suggest that the unusual low-temperature transport behavior of SmB6 is likely to be related to the pronounced surface states sitting inside the band hybridization gap and the presence of a topological Kondo insulating state. Recent result on rare earth Hexboride will be shown. [Preview Abstract] |
Monday, March 3, 2014 2:42PM - 2:54PM |
D43.00002: The changes in surface states in SmB$_{6}$ depending on non-magnetic/magnetic dopants B.Y. Kang, Chul-Hee Min, M.S. Song, B.K. Cho After the metallic surface states in SmB$_6$ have given rise to the constant resistivity at \textit{T} $<$ 4 K [1], it has received intensive attention because SmB$_6$ can be a topological insulator that possesses strongly correlated electrons in contrast with the 3D band topological insulators, \textit{i.e.} Bi$_2$Se$_3$, Bi$_2$Te$_3$ and Sb$_2$Te$_3$. Here, we show the differences of electrical transport properties in high-quality single crystals of Sm$_{1-x}$\textit{R}$_x$B$_6$ (\textit{R} = La, Ce) which are synthesized using high-temperature \textit{Al} solution growth methods. When non-magnetic La ion 3\% is doped in SmB$_6$, the surface states are maintained, but, when magnetic Ce ion 3\% is doped, they are destroyed. Our results indicate that these are topological surface states that are sensitive to magnetic ion, which is breaking time reversal symmetry. Moreover, we will discuss about quantum percolation limit obtained from the electric properties of Sm$_{1-x}$La$_x$B$_6$ (x = 0, 0.03, 0.1, 0.2, 0.25, 0.3, 0.35, 0.6, 0.8, 0.9), and the resistivity vs. temperature of doped SmB$_6$ in detail.\\[4pt] [1] Wolgast, S. \textit{et al.} Low temperature surface conduction in the Kondo insulator SmB$_6$, arXiv:1211.5105 (2012) [Preview Abstract] |
Monday, March 3, 2014 2:54PM - 3:06PM |
D43.00003: Observation of possible topological in-gap surface states in the Kondo insulator SmB$_{6}$ by photoemission Juan Jiang, Sheng Li, Tong Zhang, Zhe Sun, Fei Chen, Zirong Ye, Min Xu, Qingqin Ge, Shiyong Tan, Xiaohai Niu, Miao Xia, Binping Xie, Yufeng Li, Xianhui Chen, Haihu Wen, Donglai Feng SmB$_{6}$, a well known Kondo insulator, exhibits transport anomaly at low temperature which is usually attributed to some ``in-gap'' states. While recent theoretical calculations and transport measurements suggest that these in-gap states could be ascribed to topological surface states. SmB$_{6}$ thus might be the first realization of topological Kondo insulator (TKI). Here by performing angle-resolved photoemission spectroscopy (ARPES), we directly observed several dispersive states within the hybridization gap of SmB$_{6}$, which show negligible k$_{z}$ dependence, indicative of their surface origin. Furthermore, the photoemission circular dichroism of the in-gap states suggests the chirality of the orbital angular momentum, and these states vanish simultaneously with the hybridization gap around 150 K. These all strongly suggest their possible topological origin. [Preview Abstract] |
Monday, March 3, 2014 3:06PM - 3:18PM |
D43.00004: Kondo hybridization and the origin of metallic states at the (001) surface of SmB$_{6}$ Emmanouil Frantzeskakis, Nick de Jong, Berend Zwartsenberg, Yingkai Huang, Yu Pan, Xin Zhang, Jiuxing Zhang, Fanxing Zhang, Lihong Bao, Ojiyed Tegus, Andrei Varykhalov, Anne de Visser, Mark Golden Is SmB$_{6}$ an ideal topological insulator with states of topological character located in a Kondo hybridization gap? SmB$_{6}$ could be the first of a new material class of topological Kondo insulators. We present high-resolution ARPES data showing that Kondo hybridization is the key to unraveling the origin of two metallic states observed in the electronic structure of SmB$_{6}$(001). One is of bulk origin, while the other represents a good candidate for a topological surface state. However, before this claim is substantiated by measuring its massless dispersion relation, our data raises the bar in terms of the energy resolution required, as we uncover strong renormalization of the hybridization gaps compared to theory. Our results map the electronic landscape in SmB$_{6}$, pointing the way for future work in the quest of Dirac cones in the first topological Kondo insulator. [Preview Abstract] |
Monday, March 3, 2014 3:18PM - 3:30PM |
D43.00005: SmS: a mixed valence semi-metal with topological band structure Jian-Zhou Zhao, Feng Lu, Hongming Weng, Zhong Fang, Xi Dai The electronic structure of typical mixed valence compound SmS has been revisited by applying the local density approximation(LDA) plus Gutziwiller method. We predict that the black phase of SmS is a narrow gap semiconductor with band structure strongly renormalized by correlation effect. While for the golden phase of SmS, which will be stabilized under pressure, the electronic structure is similar to the strong three dimensional topological insulator with non-trivial $Z_2$ index but zero indirect gap. The surface state for (001), (111) and (011) surfaces have been obtained by our LDA+Gutzwiller calculations, indicating its non-trivial topological nature. We have also calculated the thin film sub band structure of SmS growing along both (001) and (111) directions. Our calculations show that the double layer thin film shown along the (111) direction is a 2D topological insulator. [Preview Abstract] |
Monday, March 3, 2014 3:30PM - 3:42PM |
D43.00006: Topological Phase Transition in the SmS Kondo Insulator under pressure Zhi Li, Jin Li, Peter Blaha, Nicholas Kioussis Employing LDA$+U $electronic structure calculations we predict that SmS undergoes a topological phase transition from the trivial Kondo insulator (KI) black phase to a topological metallic gold phase under hydrostatic pressure. The underlying mechanism is the pressure-induced change of the 4$f $level from below to above the bottom of the 5$d$ conduction band, leading to a \textit{df} band inversion, a parity sign reversal, and the concomitant change of the topological invariant. This provides the first material realization of the topological classification of KIs proposed by Dzero \textit{et al}. [Preview Abstract] |
Monday, March 3, 2014 3:42PM - 3:54PM |
D43.00007: Cubic Topological Kondo Insulators Victor Alexandrov, Maxim Dzero, Piers Coleman Current theories of Kondo insulators employ the interaction of conduction electrons with localized Kramers doublets originating from a tetragonal crystalline environment, yet all Kondo insulators are cubic. Here we develop a theory of cubic topological Kondo insulators involving the interaction of spin quartets with a conduction sea. The spin quartets greatly increase the potential for strong topological insulators, entirely eliminating the weak-topological phases from the diagram. We show that the relevant topological behavior in cubic Kondo insulators can only reside at the lower symmetry X or M points in the Brillouin zone, leading to a three Dirac cones in ARPES measurements. [the work is accepted for publication in PRL] [Preview Abstract] |
Monday, March 3, 2014 3:54PM - 4:06PM |
D43.00008: Topological phase transition on honeycomb lattice with third neighbor hooping Yao-Hua Chen, Hsiang-Hsuan Hung, C.S. Ting The topological phases originating in spin-orbital coupling systems have attracted great attention in modern condensed matter physics. Many interesting phenomena have been found in recent theoretical and experimental works, such as the integer and fractional quantum Hall effect, topological band insulator, topological Mott insulator, and topological superconductor. We have investigated the topological phase transition on honeycomb lattice with third neighbor hooping by employing the cellular dynamical mean-field theory combining with the continuous-time Monte Carlo method. The non-trivial topological insulator can be found by observing the spin Chern number directly, and the effects of the third neighbor hopping and interaction are also discussed. Furthermore, we also provide the whole phase diagram for interaction, third neighbor hopping, and temperature. [Preview Abstract] |
Monday, March 3, 2014 4:06PM - 4:18PM |
D43.00009: Interaction-induced topological orbital phases in tetragonal t2g systems Yuan-Yen Tai, C.-C. Joseph Wang, Jian-Xin Zhu, Matthias J. Graf, Chin-Sen Ting We theoretically predict the anomalous orbital Hall(AOH) effect based on an reliable effective two-orbital model. This model reveals four Dirac-like linear dispersion with C$_{4v}$ symmetry. We find a ground state with spontaneous orbital current order driven by inter-orbital Coulomb interaction. The orbital order breaks the degeneracy of Dirac linear dispersion and has topologically nontrivial Chern number $C = \pm 2$. With open boundaries, we show the edge states are topologically protected. We find a new Z$_2$ topological insulating phase protected by time reversal(TR) symmetry and orbital exchange symmetry when spin degrees of freedom are incorporated. [Preview Abstract] |
Monday, March 3, 2014 4:18PM - 4:30PM |
D43.00010: Plutonium hexaboride is a correlated topological insulator Xiaoyu Deng, Kristjan Haule, Gabriel Kotliar We predict that plutonium hexaboride (PuB$_6$) is a strongly correlated topological insulator, with Pu in an intermediate valence state of Pu$^{2.7+}$. Within the combination of dynamical mean field theory and density functional theory, we show that PuB$_6$ is an insulator in the bulk, with non-trivial $Z_2$ topological invariants. Its metallic surface states have large Fermi pocket at $\bar{X}$ point and the Dirac cones inside the bulk derived electronic states causing a large surface thermal conductivity. PB$_6$ has also a very high melting temperature therefore it has ideal solid state properties for a nuclear fuel material. [Preview Abstract] |
Monday, March 3, 2014 4:30PM - 4:42PM |
D43.00011: Topological crystalline Kondo insulators and universal topological surface states of SmB$_6$ Mengxing Ye, J.W. Allen, Kai Sun We prove theoretically that certain strongly correlated Kondo insulators are topological crystalline insulators with nontrivial topology protected by crystal symmetries. In particular, we find that SmB$_6$ is such a material. In addition to a nontrivial Z$_2$ topological index protected by time reversal symmetry, SmB$_6$ also has nontrival mirror Chern numbers protected by mirror symmetries. On the $(100)$ surface of SmB$_6$, the nontrivial mirror Chern numbers do not generate additional surface states beyond those predicted by the Z$_2$ topological index. However, on the $(110)$ surface, two more surface Dirac points are predicted. Remarkably, we find that for SmB$_6$ both the Z$_2$ topological index and the mirror Chern numbers are independent of microscopic details, which enable us to obtain surface state properties that are universal. [Preview Abstract] |
Monday, March 3, 2014 4:42PM - 4:54PM |
D43.00012: Unusual in-gap and hybridized states of a topological Kondo insulator candidate, SmB$_{6}$ B. Zhou, Z.K. Liu, S.H. Yao, H.T. Yuan, Y. Zhang, M.H. Lu, Y.F. Chen, H. Huang, X. Dai, Z. Fang, Y. Cui, H.Y. Hwang, Z. Hussain, Z.-X. Shen, S.-K. Mo, Y.L. Chen Topological Kondo insulators represent a new type of topological insulator, in which a Kondo insulator exhibits non-trivial topological electronic structure and possesses an odd number of surface Dirac fermions in the bulk energy gap. Using angle-resolved photoemission spectroscopy (ARPES) and electric transport measurements, we investigated the electronic structure of SmB$_{6}$, a topological Kondo insulator candidate proposed recently. More details will be introduced in the presentation. [Preview Abstract] |
Monday, March 3, 2014 4:54PM - 5:06PM |
D43.00013: Scanning Tunneling Microscopy and Spectroscopy of Kondo Insulator SmB6 Di Chen, Yuntao Li, Xunchi Chen, Zhiling Dun, Geoffrey Rojas, Haidong Zhou, Petro Maksymovych, Phillip First, Zhigang Jiang Kondo insulator SmB6 has recently been predicted to be a candidate three-dimensional topological insulator with truly insulating bulk. Here we report on a pilot scanning tunneling microscopy and spectroscopy (STS) study of the surface properties of single crystal SmB6. We find that a room-temperature cleaved SmB6 (001)-surface is mostly disordered, while large 3x1 reconstructed areas can be obtained by annealing the samples at 1450\textordmasculine C. Without cleaving, the as-grown (001)-surface also exhibits a 3x1 reconstruction after room-temperature sputtering, and annealing at 1450 \textordmasculine C. At low temperatures, a gap-like feature appears in the measured STS spectra, and finite density of states is observed at the Fermi energy. [Preview Abstract] |
Monday, March 3, 2014 5:06PM - 5:18PM |
D43.00014: Large high quality crystals of the Topological Kondo Insulator, SmB$_{6}$ Geetha Balakrishnan, Monica Ciomaga Hatnean, D.McK. Paul, M.R. Lees SmB$_{6}$ has been predicted to be a Topological Kondo Insulator, the first strongly correlated heavy fermion material to exhibit topological surface states. High quality crystals are necessary to investigate the topological properties of this material. Single crystal growth of the rare earth hexaboride, SmB$_{6}$, has been carried out by the floating zone technique using a high power xenon arc lamp image furnace. Large, high quality single-crystals are obtained by this technique. The crystals produced by the floating zone technique are free of contamination from flux materials and have been characterised by resistivity and magnetisation measurements. These crystals are ideally suited for the investigation of both the surface and bulk properties of SmB$_{6}$. [Preview Abstract] |
Monday, March 3, 2014 5:18PM - 5:30PM |
D43.00015: Low-temperature magnetotransport in topological Kondo insulator SmB$_6$ Yasuyuki Nakajima, Paul Syers, Xiangfeng Wang, Renxiong Wang, Johnpierre Paglione The Kondo insulater SmB$_6$ is a promising candidate for realizing a topological Kondo insulator, where topologically non-trivial surface states can be realized in the Kondo hybridization gap driven by strong correlation. Although recent experimental studies have revealed the existence of metallic surface states in SmB$_6$, the non-trivial nature of the surface states remains to be conclusively verified. We report a detailed study of the magnetoresistance of SmB$_6$ at milliKelvin temperatures, reporting strong indications of the topological nature of the surface states in SmB$_6$. [Preview Abstract] |
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