Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session L02: Topological Materials  Optical and other SpectroscopyFocus

Hide Abstracts 
Sponsoring Units: DMP Chair: Kenneth Burch, Boston College Room: BCEC 107A 
Wednesday, March 6, 2019 11:15AM  11:51AM 
L02.00001: Magnetoinfrared Spectroscopy of Topological Materials Invited Speaker: Zhigang Jiang The topological nature of a material is not only reflected on the surfaces or along the edges but also hidden inside the material in the bulk electronic structure. In this talk, I will describe how the bulksensitive magnetoinfrared spectroscopy technique can be used to probe the electronic structure topology. I will use transitionmetal pentatellurides (ZrTe_{5} and HfTe_{5}, Dirac semimetals) and monopnictides (NbP, Weyl semimetals) as material examples. For the Dirac semimetals, we find that the observed Landau level transitions are similar to that in graphene but with a finite mass and the Zeeman effect opens the inverted band gap due to the large gfactor in the materials. For the Weyl semimetals, we find that the magnetic field opens a sizable gap at the charge neutrality point (Weyl annihilation) due to the finite coupling between the Weyl points and a new optical transition rule appears when the magnetic field breaks the axial symmetry. For both material systems, a semiquantitative agreement between the experiment and the effective Hamiltonian model calculation is achieved. 
Wednesday, March 6, 2019 11:51AM  12:03PM 
L02.00002: Quantum oscillation evidence of topological semimetal phase in ZrSnTe Jin Hu, Yanglin Zhu, Zhijie Tang, Zhiqiang Mao, David E Graf, Xin Gui, Weiwei Xie The layered WHM  type (W=Zr/Hf/La, H=Si/Ge/Sn/Sb, M=S/Se/Te) materials represent a large family of topological semimetals, which provides an excellent platform to study the evolution of topological semimetal state with the fine tuning of spinorbit coupling and structural dimensionality for various combinations of W, H and M elements. In this work, through high field de Haas–van Alphen (dHvA) quantum oscillation studies, we have found evidence for the predicted topological nontrivial bands in ZrSnTe. Furthermore, from the angular dependence of quantum oscillation frequency, we have revealed the threedimensional Fermi surface topologies of this layered material owing to strong interlayer coupling. 
Wednesday, March 6, 2019 12:03PM  12:15PM 
L02.00003: Identification of candidate species for intercalation doping of ZrTe_{5} Normand Modine ZrTe_{5} is an interesting topological quantum material that is predicted to be a Dirac semimetal at the boundary between weak and strong topological insulator phases. In topological materials, it is highly desirable to control the doping of the material in order to adjust the Fermi level to coincide with features in the band structure. Since ZrTe_{5} is a layered material, one approach to accomplishing this goal is “intercalation doping," in which a dopant diffuses between the layers of the material. We have used van der Waalscorrected density functional theory to investigate the intercalation of a variety of atoms into ZrTe_{5} with the goal of identifying promising candidates for intercalation doping. We have calculated bulk absorption energies and diffusion barriers, and where bulk interlayer diffusion rates are reasonably rapid, we have also calculated the corresponding surface properties. We conclude that Li and Pd are promising candidates for intercalation doping of ZrTe_{5}. 
Wednesday, March 6, 2019 12:15PM  12:27PM 
L02.00004: Measurements of outofplane magnetoresistance in ZrSiS, ZrSiSe, and HfSiS microstructures Kent Shirer, Kimberly Modic, Tino Zimmerling, Markus Koenig, Leslie Schoop, Andrew Mackenzie Topological nodalline semimetals with the general formula XSiY (X = Zr, Hf and Y = S, Se, Te) have recently attracted much experimental and theoretical interest due to their properties, particularly their large magnetoresistances and high carrier mobilities. Due to the plateletlike nature of the XSiY crystals and their extremely low residual resistivities, measurements of the resistivity along the [001] direction are extremely challenging. To accomplish such measurements, microstructures of single crystals were prepared using Focused Ion Beam techniques. Microstructures prepared in this manner have very welldefined geometries and maintain their high crystal quality, verified by the quantum oscillations we observed. We will present magnetoresistance and quantum oscillation data for currents applied along both [001] and [100] in ZrSiS, ZrSiSe, and HfSiS and discuss the role microstructuring can play in the study of these materials. 
Wednesday, March 6, 2019 12:27PM  12:39PM 
L02.00005: Revealing Optical Transitions and Carrier Dynamics within the Bulk Band Structure of Bi_{2}Se_{3} Giriraj Jnawali, Samuel M Linser, Iraj Abbasian Shojaei, Seyyedesadaf Pournia, Howard E Jackson, Leigh Smith, Ryan Need, Stephen Wilson Bismuth selenide (Bi_{2}Se_{3}) is a prototypical topological insulator which exhibits gapped states within the bulk and topologically protected conducting states on the surface. Here we use midinfrared pumpprobe spectroscopy on Bi_{2}Se_{3} nanosheets exfoliated from Bridgeman grown single crystals to map the bandedge electronic structure and interrogate carrier relaxation processes over a wide energy range (0.3 to 1.2 eV). We observe direct optical transitions from spinorbit split valence bands to the Fermi level above the lowest conduction band minimum. The photoexcited carriers thermalize rapidly to the lattice temperature within a couple of picoseconds due to optical phonon emission and scattering with the cold electron gas followed by slow electronhole recombination within 150 ps at 10 K and 50 ps at 300 K. Knowledge of electronic structure and interaction of electrons and holes within the bulk band structure provides a foundation for understanding coupling of these states with the protected surface states. 
Wednesday, March 6, 2019 12:39PM  12:51PM 
L02.00006: The thickness dependent optical nonlinearity of graphene/Bi_{2}Te_{3} heterojunction Jia Chi Lan, Jun Peng Qiao, WeiHeng Sung, Chun Hu Chen, Cheng Maw Cheng, ChaoKuei Lee The graphene like surface state of topological insulators (TIs) have been attracted plenty of attentions. However, ultralow saturation absorption resulting from the intrinsic bulk state of TIs limts its application, such as pulse laser. In this work, thickness dependent optical nonlinearity of graphene/Bi_{2}Te_{3} heterojunction saturable absorber is investigated. Unlike the low saturation intensity of Bi_{2}Te_{3 }(with order of tens W/cm^{2}), the saturation intensity of graphene/Bi_{2}Te_{3} heterojunction increases dramitically at least 4 order of magnitude. In addition, the increasing modulation depth of around 60% is characterized and the high quality 1um Qswitched solid state laser based on graphene/Bi_{2}Te_{3} heterojunction saturable absorber is accordingly performed. Finally, the possible mechanism of carrier dynamics between pn heterojunction and guideline for material design are proposed and discussed as well. 
Wednesday, March 6, 2019 12:51PM  1:03PM 
L02.00007: Measuring the Thermal Conductivity of Semiconductors and Semimetals Using Raman Spectroscopy Iraj Abbasian Shojaei, Giriraj Jnawali, Seyyedesadaf Pournia, Samuel M Linser, Howard E Jackson, Leigh Smith, Ryan Need, Stephen Wilson We present a measurement of the thermal conductivity for Bi_{2}Se_{3} and Te and semimetals at room temperature by using Raman scattering spectroscopy on a clean prepared sample on a SiO_{2} substrate. Aluminum is deposited on either side of the flake and is used as a heat sink at room temperature. Using a He/Ne laser (633 nm), we measure the Raman shift of the sample as a function of laser power between 0.1mW and 1mW. The linear red shift of Raman modes due to heating of the sample provides a measure of the temperature of the sample around the incident laser area. We calculate the thermal conductivity of the sample by solving a simplified one dimensional heat diffusion equation, ignoring the heat conduction to the ambient air and substrate. Our results for Bi_{2}Se_{3 }suggest a value of 4 W/mK for the thermal conductivity, comparable to the measurements of others; using the same technique we plan make measurements of several Weyl semimetals (eg/ WTe_{2} and NbIrTe_{4}). 
Wednesday, March 6, 2019 1:03PM  1:15PM 
L02.00008: Signature of chiral anomaly in TaP through phonon dynamics Thanh Nguyen, Mingda Li, Fei Han, Nina Andrejevic, Songxue Chi, Jaime FernandezBaca, Masaaki Matsuda, Ahmet Alatas, Esen Alp Recent theoretical predictions discussed the possibility of detecting chiral anomaly based on phonon spectra as the exotic electronic degrees of freedom in a Weyl semimetal play an important role to influence the phonon structure. I will discuss measurements made of phonon excitations on a highquality single crystal sample of typeI Weyl semimetal TaP using inelastic neutron and xray scattering spectroscopies. These measurements indicate the presence of phonon softening near the Weyl nodes which is driven by the coupling between the chiral Weyl fermions and phonons. We also observe that this coupling differs between the W1 and W2 Weyl nodes. These results provide a method to extract valuable information about the soughtafter electronphonon coupling strength. 
Wednesday, March 6, 2019 1:15PM  1:27PM 
L02.00009: Band structure of topological insulators via cyclotron resonance Andrei Pimenov In the quasiclassical approximation the cyclotron mass can be directly connected to the band structure. The analysis based on the cyclotron resonance (CR) is especially useful for thin film materials in which capping layers prevent standard approaches like ARPES. Here, using the CR experiments in the terahertz range, we obtain the band structure of topological insulators (TI) based on mercury telluride (HgTe) quantum wells. In threedimensional HgTe TI the dispersion of surface carriers is close to parabolic and it dominates the cyclotron signal. In addition, several other features are observed that can be attributed the bulk carriers. In twodimensional HgTe TI the dispersion of electrons is close to linear showing increasingly complicated character in the region of the holelike carriers. 
Wednesday, March 6, 2019 1:27PM  1:39PM 
L02.00010: Nonlinear Optical Effect of Impulsive Stimulated Raman Process in typeII Weyl Semimetal T_{d}WTe_{2 } Elizabeth Drueke, Junjie Yang, Liuyan Zhao Recent studies into Weyl semimetals with noncentrosymmetric crystal structures have revealed a wide range of second order nonlinear phenomena, including the polarizationselective photogalvanic effect and giant second harmonic generation. We here present a study of another second order nonlinear effect, impulsive stimulated Raman scattering, in the type II Weyl semimetal T_{d}WTe_{2}. Using ultrafast timeresolved optical reflectivity measurements, we demonstrate a large number of coherent phonons excited through this impulsive stimulated Raman scattering process and identify polarizationdependent selection rules for these phonons based on a symmetry analysis of the crystal structure of the material. Further, we investigate the fluence dependence of the phonons and compare this dependence to fluencedependent carrier dynamics. 
Wednesday, March 6, 2019 1:39PM  1:51PM 
L02.00011: Fermi Surfaces of FlatBand Intermetallic APd_{3} (A = Pb, Sn) Kaya Wei, KuanWen Chen, Jennifer Neu, You Lai, Greta Chappell, Yan Xin, David E Graf, Luis Balicas, Ryan Baumbach, Theo Siegrist DFT calculations for APd_{3} (A=Pb, Sn) recently revealed an interesting band structure [1] that includes: a dispersionless branch along the ΓX line, that could result in a large DOS near E_{F}, and Diraclike surface states. To test these predictions, we synthesized single crystals of PbPd_{3} and SnPd_{3} using the Czochralski growth technique and performed magnetoresistance and torque magnetometry measurements in magnetic fields up to 45 T. Through analysis of quantum oscillations, we uncover Fermi surface topographies that suggest the E_{F} is roughly 50 meV above the flat band for PbPd_{3}. This results in the flat bands only having a weak effect on the bulk properties, while the impact of the Dirac cone at the Γpoint is also limited due to it being several hundred meV above E_{F}. We will discuss detailed results of the Fermi surface topology measurements and prospects for tuning the E_{F} to meet either the flat bands or the Dirac cone. 
Wednesday, March 6, 2019 1:51PM  2:03PM 
L02.00012: Novel plasmons in quantum anomalous Hall systems Jianhui Zhou, Di Xiao, Yugui Yao, Furu Zhang We find that the inverted band structure with the Mexicanhat dispersion could enhance the interband correlation leading to a strong intrinsic plasmon excitation. Its frequency ranges from several meV to tens of meV and can be effectively tuned by the external fields. The electronhole asymmetric term splits the peak of the plasmon excitation into double peaks. The fate and properties of this plasmon excitation can also act as a probe to characterize the topological phases even in lightly doped systems. We numerically demonstrate the impact of band inversion on plasmon excitations in magnetically doped thin films of threedimensional strong topological insulators, which support the quantum anomalous Hall states (QAHE). We also study the chiral edge plasmons in QAHE and find many new and remarkable features of chiral edge plasmons. Our work thus sheds some new light on the potential applications of topological materials in plasmonics. 
Wednesday, March 6, 2019 2:03PM  2:15PM 
L02.00013: Optical circular dichroism in an antiperovskite Dirac semimetal Katsuhisa Taguchi, Takuto Kawakami, Masatoshi Sato We theoretically study selective circular dichroism in an antiperovskite type Dirac semimetal, which hosts Dirac fermions with high total angular momentum J. We find that unconventional circular dichroism depends on J : In J =1/2 Dirac fermion, nonzero circular dichroism is generated in J_{z } J'_{z }= ±1, where J_{z} and J'_{z} are the zcomponent of J of the conduction band minimum and the valance band maximum around Dirac points, respectively. It is noted that this ±1 reflects on the spin angular momentum of the polarization of the applied light. On the other hand, in J =3/2 Dirac fermion, the nonzero circular dichroism is triggered in J_{z } J'_{z }= ±3. Its origin is shown in this presentation. 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2024 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700