Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session M7: Focus Session: Topological Crystalline Insulators |
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Sponsoring Units: DMP DCMP Chair: Yoshinori Okada, Tohoku University Room: 006B |
Wednesday, March 4, 2015 11:15AM - 11:51AM |
M7.00001: Electron and spin properties of topological crystalline insulator (Pb,Sn)Se Invited Speaker: Tomasz Story Topological crystalline insulators (TCIs) constitute a new class of quantum materials with the Dirac-like metallic surface states that cross the bulk semiconductor band gap and are topologically protected by crystalline mirror plane symmetry. The TCI states have recently been experimentally observed in (Pb,Sn)Se, SnTe, and (Pb,Sn)Te for both (001) and (111) crystal surfaces. These IV-VI semiconductors undergo (at a specific tin content, temperature, and pressure) a band structure inversion driven by strong relativistic effects. The investigations of the surface electronic states by angle- and spin-resolved photoemission spectroscopy will be presented for bulk (Pb,Sn)Se monocrystals with tin content up to 37 at. {\%}, also doped with magnetic Mn 2$+$ ions. In the inverted band structure regime we found the Dirac-like topological in-gap states in the vicinity of four X points of the (001) surface Brillouin zone and observe a temperature-driven topological phase transition from a trivial insulator to a TCI state below the band inversion point. In crystals with Mn ions we demonstrate very efficient tuning of the topological transition temperature by band gap engineering effect. The spin-resolved ARPES experiments revealed a characteristic vortical electron spin polarization texture at the Dirac points. Based on spectroscopic observation we construct the composition - temperature topological phase diagram of (Pb,Sn)Se and compare it with tight-binding band structure calculations. P. Dziawa et al., Nat. Mat. 11, 1023 (2012); B.M. Wojek et al., Phys. Rev. \quad B 87, 115106 (2013); C.M. Polley et al., Phys. Rev. B 89, 075317 (2014); B.M. Wojek et al., Phys. Rev. B 90, 161202 (R) (2014). [Preview Abstract] |
Wednesday, March 4, 2015 11:51AM - 12:03PM |
M7.00002: Topological crystalline insulator states in layered materials Youngkuk Kim, Charles Kane, Eugene Mele, Andrew Rappe Topological crystalline insulator (TCI) is a topological state of materials whose topological property relies on generic crystalline symmetries. Based on first-principles calculations, we suggest new classes of topological crystalline insulators characterized by non-zero mirror Chern numbers (MCNs) hosted on the mirror-invariant plane at the boundary of the Brillouin zone (BZ). We demonstrate that the new TCI phases can be realized in layered materials, and the topological phase transitions associated with the proposed TCI phases occur under an external pressure. Our results shed light on the role of the MCNs hosted on the surface of the BZ, and open new possibilities for finding TCI materials. [Preview Abstract] |
Wednesday, March 4, 2015 12:03PM - 12:15PM |
M7.00003: Strain engineering Dirac surface states in heteroepitaxial topological crystalline insulator thin films Ilija Zeljkovic, Daniel Walkup, Badih Assaf, Kane Scipioni, Raman Sankar, Fangcheng Chou, Vidya Madhavan In newly discovered topological crystalline insulators (TCIs), the unique crystalline protection of the surface state (SS) band structure has led to a series of intriguing predictions of strain generated phenomena, such as the momentum-space tunability of the Dirac nodes. In this work, we have designed an experiment to not only generate and measure strain locally, but to also directly measure the resulting effects on the Dirac SS. We grow heteroepitaxial thin films of TCI SnTe in-situ and measure them by using high-resolution scanning tunneling microscopy (STM). Large STM images were analyzed to determine picoscale changes in the atomic positions which reveal regions of both tensile and compressive strain. Simultaneous Fourier-transform STM was then used to determine the effects of strain on the Dirac electrons. We find that strain continuously tunes the momentum space position of the Dirac points, consistent with theoretical predictions. Our experiments demonstrate the fundamental mechanism necessary for using TCIs in strain-based applications. [Preview Abstract] |
Wednesday, March 4, 2015 12:15PM - 12:27PM |
M7.00004: ABSTRACT WITHDRAWN |
Wednesday, March 4, 2015 12:27PM - 12:39PM |
M7.00005: Realization of topological phase transition in Pb$_{1-x}$Sn$_{x}$Te (111) films Chenhui Yan, Junwei Liu, Yunyi Zang, Zhenyu Wang, Jianfeng Wang, Zhidong Zhang, Lili Wang, Xucun Ma, Shuaihua Ji, Ke He, Liang Fu, Wenhui Duan, Qi-Kun Xue, Xi Chen Recently, it was confirmed that the single crystal SnTe is a Topological crystalline insulator (TCI ) by theoretical calculations and experiments. It is well known that the (001) surfaces of SnTe are the natural cleavage planes and therefore all the previous experiments for the TCI phase were performed on the (001) surfaces. The (111) surface, which is a polar surface with unpaired electrons, is very difficult to obtain by traditional crystal growth method. Here we present the epitaxial growth of high quality Pb$_{1-x}$Sn$_{x}$Te (111) films and observation of TCI phase by in-situ angle-resolved photoemission spectroscopy. The Pb$_{1-x}$Sn$_{x}$Te (111) films undergo a topological phase transition from trivial insulator to TCI via increasing the Sn/Pb ratio,accompanied by a crossover from n-type to p-type doping in the films. In addition, a sizeable Rashba effect is clearly seen in the PbTe (111) film. Our work demonstrates the manipulation of topological properties of TCI, which is crucial for future fundamental research and applications. C. Yan et al., Phys. Rev. Lett., 112, 186801 (2014). [Preview Abstract] |
Wednesday, March 4, 2015 12:39PM - 12:51PM |
M7.00006: Searching for ideal bulk insulating Pb-system topological crystalline insulator materials Genda Gu, R.D. Zhong, John Schneeloch, T.S. Liu, Jhon Tranquada, X.G. He, Wei Ku, I. Pletikosic, T. Valla The discovery of 3D topological insulator materials opened up a new research field in the condensed matter physics. However, there is no real bulk insulating topological insulator materials available for experimental research so that we can explore the new field. In order to search for the ideal bulk insulating topological insulator materials, we have grown a large number of the single crystals of Pb-system (Pb-Sn-In-Te) topological crystalline insulator. We have measured the physical properties on these single crystals by various techniques. We have studied the effect of crystal growth condition, impurity and composition on the bulk electrical conductivity of these single crystals. We try to find out which composition and crystal growth condition is the best for the ideal bulk insulating topological crystalline insulator materials. [Preview Abstract] |
Wednesday, March 4, 2015 12:51PM - 1:03PM |
M7.00007: Fe-doped Topological Crystalline Insulator SnTe Thin Films Stephen D. Albright, K. Zou, F.J. Walker, C.H. Ahn Substitution doping by magnetic elements may induce novel ground states in topological insulators (TIs) or topological crystalline insulators (TCIs). We have grown thin films of TCI SnTe with varying concentrations of Fe using molecular beam epitaxy and have characterized them using atomic force microscopy, scanning electron microscopy, and x-ray diffraction. Films doped with Fe exhibit a decreasing carrier density with increasing doping, indicating that bulk states due to Sn vacancies in our films are largely suppressed, with the topological surface states becoming dominant. We discuss the nature of the ground state of SnTe induced by Fe-doping as determined by magnetization and magneto-transport measurements. [Preview Abstract] |
Wednesday, March 4, 2015 1:03PM - 1:15PM |
M7.00008: Properties of thin film SnTe grown by molecular beam epitaxy K. Zou, Stephen D. Albright, G.H. Simon, M.D. Morales-Acosta, Eric Altman, F.J. Walker, C.H. Ahn The topological crystalline insulator SnTe exhibits multiple surface states protected by crystal symmetry. Thin films of SnTe have been grown by physical vapor deposition techniques on several substrates; these films tend to consist of a heterogeneous collection domain structures. In this talk, we report systematic studies of the structure and transport properties of SnTe films grown by molecular beam epitaxy (MBE). Combining atomic force microscopy and x-ray diffraction measurements, we find that the domains consist of crystallites with {100} and {111} surfaces. When the thickness of SnTe exceeds 400 u.c., the {100} surface becomes dominant. Transport measurements show that conduction in the films can be attributed to both Sn vacancies in bulk SnTe and the surface topological states of SnTe. [Preview Abstract] |
Wednesday, March 4, 2015 1:15PM - 1:27PM |
M7.00009: Electronic and spin structure of topological surface state in Sn-based ternary topological insulators Maia G. Vergniory, Tatiana V. Menshchikova, Igor V. Silkin, Yury M. Koroteev, Sergey V. Eremeev, Evgueni V. Chulkov We report the bulk and surface electronic properties and spin polarization of a new rich family of Sn-based ternary complex topological insulators studied by means of first principles calculations. These compounds exist in different stoichiometries: SnxAyBz (A:Sb and Bi) (B: Te and Se). The crystal structure of these compounds are characterized by alternating along hexagonal axis quintuple, septuple and nonuple layer van der Waals bonded building blocks. We reveal that the bulk band gap in these systems is about 200 meV and the spin polarization near the Dirac point is up to 85\%, one of the highest predicted hitherto. At the same family, for some of these compounds which crystal structure has ionic-covalent bonded Bi2Te3 and crystalline topological insulator SnTe atomic layers within building block the complex SOI-induced bulk band inversion caused by competition of band inversions in Bi2Te3 and in SnTe layers occurs and results in inherently nonlinear dispersion of the topological surface state. [Preview Abstract] |
Wednesday, March 4, 2015 1:27PM - 1:39PM |
M7.00010: ABSTRACT WITHDRAWN |
Wednesday, March 4, 2015 1:39PM - 1:51PM |
M7.00011: Hidden topological surface states on SnTe (111) surface Jianfeng Wang, Junwei Liu, Wenhui Duan Abundant and interesting properties of topological crystalline insulator SnTe (111) surface have been studied here. Using first-principles calculations, we show the stable structures and their related topological surface states (TSS) under different growth conditions. Surface reconstruction can induce the TSS type transition. More interestingly, the position of TSS can be hidden deeply below the surface, which depends on the interlayer relaxation. The underlying mechanism can be understood by the distortion-induced topological phase transition. Our work paves the way to control the TSS, especially to realize the physical protection in real environment. [Preview Abstract] |
Wednesday, March 4, 2015 1:51PM - 2:03PM |
M7.00012: Surface state of superconducting topological crystalline insulator Tatsuki Hashimoto, Keiji Yada, Masatoshi Sato, Yukio Tanaka Topological crystalline insulator SnTe has Dirac fermions protected by mirror symmetry [1,2]. (001) surface is particularly unique in mixing of two Dirac cone. It has been known that In doped SnTe become superconductor at low temperature. After the observation of zero-bias conductance peak which may originate from Andreev bound state in 2012 [3], In-SnTe has drawn attention as a candidate of topological superconductor and topological crystalline superconductor. Although it has been indicated the possibility of the existence of topological surface state by the experiments, theoretical calculation of the surface states for this material has not been done before now. First, we consider possible pair potentials for In-SnTe from crystal point group. Next, we calculate surface state for the possible pairings. Here, we use the recursive Green's function method and calculate in the semi-finite system. As a result, we find that wide variation of surface states can appear depending on the pairing symmetry and surface direction. \\[4pt] [1] L. Fu et al., Phys. Rev. Lett. 106, 106802 (2011).\\[0pt] [2] Y. Tanaka et al., Nat. Phys. 8, 800(2012).\\[0pt] [3] S. Sasaki et al., Phys. Rev. Lett. 109, 217004 (2012). [Preview Abstract] |
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