Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session D19: Experimental Progress in Nonmagnetic Solid-State Topological Insulators |
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Sponsoring Units: DCMP Chair: Yiming Xu Room: Room 211 |
Monday, March 6, 2023 3:00PM - 3:12PM |
D19.00001: Lateral Coupling of 2D Dirac Plasmons in Thin Films of Topological Insulator Bi2Se3. Saadia Nasir, Stephanie Law, Vish Mambakkam, Zhengtianye Wang 2D Dirac plasmon polaritons (DPPs) excited on the surfaces of the 3D topological insulator Bi2Se3 have resonance frequencies in the terahertz range which has applications in security, wireless communication, and so on. Patterning thin films of Bi2Se3 into stripes of width W provides an additional momentum of π/W to the incoming photons, which then can excite DPPs by overcoming the momentum mismatch. When the thickness of films is much smaller than the wavelength of the incident light, the DPPs are excited on the top and bottom surfaces simultaneously and couple to each other resulting in an acoustic mode and an optical mode. Vertical coupling of DPPs in Bi2Se3 thin films is generally well-understood but there is no clear understanding of how the plasmons couple to each other in the same plane. We explored the effect of in-plane coupling on the resonance frequency of the DPPs by changing the gap size between the stripes while keeping stripe width and film thickness constant. We show that DPPs exhibit dipole-dipole type coupling which becomes negligible when the lattice constant exceeds approximately 2.8 times the stripe width. This value is comparable to results found for plasmons localized on the metallic nanoparticles or graphene micro-discs. Insight into the in-plane coupling of DPPs can be useful in designing TI-based metasurfaces to exploit THz light. |
Monday, March 6, 2023 3:12PM - 3:24PM |
D19.00002: Extraordinary Bulk Behavior in 3d-based Strongly Correlated Insulators FeSi and FeSb2 Keenan Avers, Yun Suk Eo, Jarryd Horn, Hyeok Yoon, Shanta Saha, Alonso Suarez, Michael Fuhrer, Johnpierre Paglione Topological Kondo insulators, such as SmB6, are a class of materials in which Kondo hybridization between conduction electrons and localized $f$-electrons opens a bulk band gap directly at the Fermi level. A consequence of this process can result in Dirac surface states and provides a platform for investigation of strongly correlated 2D electron physics on a bulk material. However, it remains an open question if simpler d-electron based correlated insulators could manifest similar physics. To this end we investigated electrical transport of the 3d-based correlated insulators FeSi and FeSb2. By using a double-sided Corbino disk transport geometry, we show unambiguous evidence of a surface conductance in both of these materials, although their topological nature is called into question by our results which show evidence of localization. In particular, FeSi can exhibit sheet conductance in excess of the Mott-Ioffe-Regal limt (h/e2) of a 2D electron gas, which suggests the surface of FeSi is a 2D variable range hopping system distinct from the bulk. In addition, by using the inverted resistance technique with a 4-terminal Corbino disk, we extract the bulk resistivity as a function of temperature. Similar to SmB6, the bulk resistivity of FeSi and FeSb2 are confirmed to exponentially increase by 8-9 orders of magnitude from 300 K to 2 K, demonstrating the bulk of these materials are excellent insulators, which provides an ideal platform for studying correlated 2D physics, regardless of topology. |
Monday, March 6, 2023 3:24PM - 3:36PM |
D19.00003: Charge transfer and friction tensor of adsorbate on the SSH chain Luis F Martinez-Gomez, Raphael F Ribeiro Due to their novel and unique electronic properties, topological phases of matter hold great promise for future applications in quantum information, spintronics, and thermoelectrics. However, surface interactions of topological insulators and molecules have yet to be harnessed for chemical catalysis, and the underlying question of whether these new phases of matter can be employed to achieve efficient and selective synthesis remains open. In this presentation, I will describe the main results of our recent study of the electron occupancy and electronic friction of a molecular system adsorbed on a polyacetylene chain in the trivial, metallic, and topological phases. We find that the characteristic signatures of the topological phase transition are manifested in these molecular observables. In addition, the topological phase provides significant advantages and robustness over the metallic for electron donation into the molecular system. This work supports the perspective that topological matter offers a promising direction for future surface reactions and chemisorption applications.
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Monday, March 6, 2023 3:36PM - 3:48PM |
D19.00004: Visualizing near-coexistence of massless Dirac electrons and ultra-massive saddle point electrons Nurit Avraham, Abhay Kumar Nayak, Jonathan Reiner, Hengxin Tan, Huixia Fu, Henry Ling, Chandra Shekhar, Claudia Felser, Tami Pereg-Barnea, Binghai Yan, Haim Beidenkopf Strong singularities in the electronic density of states aenhance correlation effects and play a key role in determining the ordering instabilities in various materials. Recently high order van Hove singularities (VHS) with diverging power-law scaling have been classified in single-band electron models. We show that the 110 surface of Bismuth exhibits a remarkable power-law divergence of the DOS, with unusually high exponent, arising from high-order VHS presented on this surface. Spectroscopic mapping of the surface band structure using scanning tunneling microscopy and spectroscopy shows that this high-order VHS occurs in conjunction with a highly anisotropic Dirac band crossing located at the center of the surface Brillouin zone. The enhanced power-law divergence is shown to originate from the anisotropic flattening of the Dirac band just above the Dirac node. Such near-coexistence of massless Dirac electrons and ultra-massive saddle points enables to study the interplay of high order VHS and Dirac fermions. |
Monday, March 6, 2023 3:48PM - 4:00PM |
D19.00005: Observation and creation of symmetry-dictated topological states in a two-dimensional insulator, 1T’-MoTe2 Hyo Won Kim, SEOUNGHUN KANG, Young-Woo Son Topological insulators (TIs) show protected metallic states on their boundaries of insulating bulks that can be either edges, surfaces, interfaces or dislocations. Symmetry of the crystal structures further diversifies these boundary states and classifies TIs with different topological index. In three-dimension (3D), the surface states protected by symmorphic mirror lines or non-symmorphic glide lines are proposed and experiments consistent with a part of the proposals are reported. Dislocations in 3D TIs also hold significant importance in revealing such characteristics but their intrinsic embedding structures inside 3D bulk hinder their direct detections that may be possible in lower dimensional TIs. In two-dimensional TIs, however, not only direct observation of topological states on grain boundaries but also interplays between crystal symmetry and topologically protected states have not been reported yet. Here, we present the first direct evidence of one-dimensional metallic states protected by non-symmorphic symmetry of glide reflection grain boundary [1] and a noble method for creation of grain boundaries in a topological insulating two-dimensional transition metal dichalcogenide (TMD), 1T’-MoTe2. By investigating electronic structures along two different grain boundaries of as-grown MoTe2 using scanning tunneling microscope (STM) and first-principles calculations, we clearly demonstrate evidences of a topologically protected state along a grain boundary with non-symmorphic symmetry and its absence along the other boundary with symmorphic one. |
Monday, March 6, 2023 4:00PM - 4:12PM |
D19.00006: Observation of Chiral Phonons with Giant Magnetic Moments in a Topological Crystalline Insulator Felix G Hernandez, Andrey Baydin, Swati Chaudhary, Fuyang Tay, Ikufumi Katayama, Jun Takeda, Hiroyuki Nojiri, Anderson Okazaki, Paulo Rappl, Eduardo Abramof, Martin A Rodriguez-vega, Gregory A Fiete, Junichiro Kono Chiral phonons present peculiar properties in magnetic fields such as: magnetic circular dichroism, phonon Zeeman effect and phonon diamagnetic shift. Recent experimental studies reported magnetic moment values in a broad range up to several Bohr magnetons. On the other hand, theoretical reports predicted the dependence of the phonon magnetic moment on electronic contributions. Here, we present experiments in a set of thin films of the pseudobinary alloy Pb(1−x)Sn(x)Te which is known to show an x-dependent topological phase transition for x > 0.32 and has exhibited chiral phonons in strong magnetic fields for x = 0. At low temperatures and under magnetic fields up to 29.5 T, two optical phonons modes acquired circular polarization with opposite handedness. While the topologically trivial films (x |
Monday, March 6, 2023 4:12PM - 4:24PM |
D19.00007: Magneto-thermopower and planar Hall effect in Sb2Te3 epitaxial films* Ravinder Kumar, Prabesh Bajracharya, Ezana R Negusse, Ryan Raxon, Rajeswari M Kolagani, Ramesh C Budhani Even though the sesqui-chalcogenide Sb2Te3 is a well-known thermoelectric material, the effect of the magnetic field on its Seebeck coefficient remains unexplored [1]. The measurements of magneto-thermopower are particularly significant since Sb2Te3 has been established as a topological insulator and may exhibit exotic magneto-thermal transport. Here, we report measurements of magneto-thermopower (MTP), anisotropic magnetoresistance (AMR) and planar Hall effect (PHE) on Sb2Te3 thin films grown epitaxially on (0001)-face of sapphire with pulsed laser ablation technique. The film exhibits metallic behaviour with a room temperature charge carrier density and mobility of an order of magnitude ~ 1019 cm-3 and ~ 102 cm2V-1S-1, respectively. The non-linear field dependence of the Hall coefficient below 30 K suggests a dominant two-carrier transport at lower temperatures. We achieve a nominal room temperature Seebeck coefficient of ~ + 51.0 μV/K, which decreases with temperature and becomes ~ - 3.4 μV/K at 10 K. The sign crossover of the Seebeck coefficient occurs around 30 K. The out-of-plane application of a moderate magnetic field (≤ 9 T) at 300 K enhances the MTP by more than 9%. We observe AMR and PHE amplitudes of an order of magnitude larger than in Bi2Te3 [2,3]. The study of MTP, AMR and PHE on non-magnetic Sb2Te3 epitaxial thin films may find applications in the field of thermoelectric generation and the development of Hall sensors. |
Monday, March 6, 2023 4:24PM - 4:36PM Author not Attending |
D19.00008: Transport in the ultra-quantum limit in topological pentatelluride HfTe5 Jinyu Liu, Laurel E Winter, Michael T Pettes, Luis A Jauregui Topological pentatellurides, ZrTe5/HfTe5, show intriguing quantum transport properties. One of the unique characteristics is the extremely small Fermi surface consisting of massive Dirac fermions. This allows to reach the quantum limit of the system at a relatively low magnetic fields (B). Under the magnetic fields far above the quantum limit, all electrons are spin polarized and pushed into the zeroth Landau level. The increasing Zeeman energy and cyclotron energy under the magnetic field may lead to band inversion as the zeroth Landau bands cross with each other, as seen in a recent magneto-infrared spectroscopy study. We have investigated the quantum transport properties of HfTe5 under pulsed magnetic fields and found signatures of enhanced conductivity and sign changes of Hall resistivity, pointing to a Liftshitz transition, under perpendicular magnetic fields. With the in-plane magnetic field, where B is parallel to the current direction, the longitudinal magnetoresistance shows a negative magnetoresistance that depends on temperature and magnetic field orientation. This might be understood by the Zeeman splitting of the bands. Our quantum transport results shed light on how the electronic property evolves in the ultra-quantum limit in HfTe5. |
Monday, March 6, 2023 4:36PM - 4:48PM |
D19.00009: Magnetotransport in graphene/Pb0.24Sn0.76Te heterostructures: finding a way to avoid catastrophe Gregory Stephen, Ivan I Naumov, Nicholas A Blumenschein, Y.-J. Leo Sun, Jennifer E DeMell, Sharmila N Shirodkar, Pratibha Dev, Patrick J Taylor, Jeremy T Robinson, Paul M Campbell, Aubrey T Hanbicki, Adam L Friedman While heterostructures are ubiquitous tools enabling new physics and device functionalities, the palette of available materials has never been richer. Combinations of two emerging material classes, two-dimensional materials and topological materials, are particularly promising because of the wide range of possible permutations that are easily accessible. Individually, both graphene and Pb0.24Sn0.76Te (PST) are widely investigated for spintronic applications because graphene’s high carrier mobility and PST’s topologically protected surface states are attractive platforms for spin transport. Here, we combine monolayer graphene with PST and demonstrate a hybrid system with properties enhanced relative to the constituent parts. Using magnetotransport measurements, we find carrier mobilities up to 20,000 cm2/Vs and a magnetoresistance approaching 100%, greater than either material prior to stacking. We also establish that there are two distinct transport channels and determine a lower bound on the spin relaxation time of 4.5 ps. The results can be explained using the polar catastrophe model, whereby a high mobility interface state results from a reconfiguration of charge due to a polar/non-polar interface interaction. Our results suggest that proximity induced interface states with hybrid properties can be added to the still growing list of behaviors in these novel materials. |
Monday, March 6, 2023 4:48PM - 5:00PM |
D19.00010: Dual topology modulated Dirac electron transports in Low-dimensional Topological Insulator Superlattices Rui Sun, Hao-pu Xue, Dali Sun, Zhao-hua Cheng Dual topological insulators, simultaneously protected by time reversal symmetry and crystalline symmetry, open great opportunities to explore different symmetry protected metallic surface states. However, the conventional dual topological states located on different facets hinders integration into planar opto-electronic/spintronic devices. Here, we construct topological super-lattices (TSLs) with dual topology, Bi2Se3-(Bi2/Bi2Se3)N with limited topological layers N. Angle resolved photoelectron emission spectroscopy (ARPES) demonstrates the coexistence of surface states from the topological insulator (TI) and topological crystalline insulator (TCI) on the Bi2Se3 facet. Further, the stacking-sequence dependent quantum transport experiments reveal the unconventional weak antilocalization effect (WAL) with WAL coefficient larger than 1<!--[if gte msEquation 12]> style='mso-bidi-font-style:normal'>a>1, confirming the existence and tunability of spin polarized dual-topological bands on the Bi2Se3 facet. Most importantly, we identify the spin polarized surface electrons from dual topological bands exhibit circularly and linearly polarized photo-galvanic effect(C,LPGE) simultaneously under polarized light illumination when excited surface electrons are mutually coupled. Our results shed light on studies of this dual topological class with distinguished topological manifestations coexisting on one facet and multiple topological phases engineering for opto-electronic/spintronic applications. |
Monday, March 6, 2023 5:00PM - 5:12PM |
D19.00011: Quantum electron transport in ternary transition metal chalcogenide TaIrTe4 Jian Tang, Siyuan Ding, Yong Li, Tiema Qian, Anyuan Gao, Kenji Watanabe, Takashi Taniguchi, David C Bell, Kenneth S Burch, Youguo Shi, Ni Ni, Suyang Xu, Xiaofeng Qian, Qiong Ma Pristine topological van der Waals (vdW) crystals are exciting material platforms to study topology in a highly-tunable way. Ternary transition metal chalcogenides MM’X4 (M = Nb, Ta and M′ = Ir, Rh) are expected to show rich topological characters: In 3D they are type-II Weyl semimetals with long Fermi arcs; In 2D they are topological insulators (TI) with sizable topological gaps. Particularly bilayer TaIrTe4 is predicted to be a non-centrosymmetric 2D TI with intrinsic ferroelectric ordering. Despite the interest, the studies on thin-layer TaIrTe4 have been very limited due to their air-sensitive nature. We successfully fabricated dual-gated monolayer and bilayer TaIrTe4 devices. The number of layers and stacking configuration were confirmed by cross-section TEM measurements. We performed electron transport experiments to study their topological and correlated properties. In this talk, we report on our experimental observations of these devices. |
Monday, March 6, 2023 5:12PM - 5:24PM |
D19.00012: Magnetic Field Dependent Effects on Nonlocal Photocurrents in Topological Insulators Henry C Travaglini, Dong Yu Topological insulators (TIs) are a remarkable class of materials due to their linear dispersion relation owing to their time-reversal symmetry-protected Dirac Cones, which have recently displayed millimeter-long diffusion lengths with a highly tunable Fermi level. Motivated by the hypothesis that these highly extended photocurrents are likely reliant on the topological surface states, we perform illuminated magnetoresistance studies on Sb-doped Bi2Se3 as a function of temperature, gate voltage, and field angle of incidence to study photo-doped weak antilocalization and Aharanov-Bohm effect behaviors. Our results provide clues about the nature of the carriers responsible for these remarkably nonlocal photocurrents which may be due to the carrier states forming an exciton condensate. |
Monday, March 6, 2023 5:24PM - 5:36PM |
D19.00013: Superior thermoelectric properties and ultralow thermal conductivity of 2D topological jacutingaite M2M’X3 (M = Ni, Pd, or Pt; M’ = Zn, Cd, or Hg; X = S, Se, or Te) family Rovi Angelo Villaos, Ali Sufyan, Zhi-Quan Huang, Chia-Hsiu Hsu, Guoqing Chang, Feng-Chuan Chuang Two-dimensional thermoelectric materials offer a sustainable solution to the challenges of an ever-increasing global demand for energy. Recently, topological materials have been demonstrated to possess excellent thermoelectric properties due to their unconventional electronic structure and unique boundary states. In particular, the jacutingaite-family M2M’X3 (M = Ni, Pd, or Pt; M’ = Zn, Cd, or Hg; X = S, Se, or Te), has attracted research attention due to their high stability and topological phase. Using first-principles calculation under the hybrid functional approach coupled with the Boltzmann transport theory, we investigate the thermoelectric properties of the monolayer topological jacutingaite materials. Twelve materials manifest a topological insulating (TI) phase with bandgaps reaching up to 261.5 meV. Surprisingly, these 12 non-trivial materials exhibit good thermoelectric properties, with the figure-of-merit (ZT) reaching greater than 1.0 within the 100 K to 800 K temperature range. Moreover, the ZT of Ni2HgTe3 (p-type) and Pt2HgTe3 (n-type) reaches up to 3.6 and 4.6, respectively. The excellent thermoelectric properties are due to their high power factor and extremely low lattice thermal conductivity, resulting in superior thermoelectric performance compared to the most current state-of-the-art thermoelectric materials. Our findings provide a new playground of materials in which non-trivial topological properties with outstanding thermoelectric performance coexist. |
Monday, March 6, 2023 5:36PM - 5:48PM |
D19.00014: Anisotropic Properties in Two-Dimensional Topological Insulator Candidates Ta2M3Te5 (M = Pd, Ni) Fei Wang, Abin Joshy, Qiaohui Zhou, Xin Lu, Jiang Wei, Pavel Sorokin, Konstantin Larionov, Liubov Yu Antipina In a two-dimensional topological insulator (2DTI), the insulating bulk band's nontrivial topology, protected by time-reversal symmetry, allows for creating unique, back scattering-free edge states. Therefore, the potential for 2DTI to be used in spintronics and quantum qubits is very promising. 2DTI has, however, only been validated in a few systems. Ta2M3Te5 (M=Pd, Ni) has recently been proposed as a possible 2DTI candidate that can be modified by strain. Ta2M3Te5 (M=Pd, Ni) also features an anisotropic in-plane crystal structure. This anisotropy may result in an anisotropic energy dispersion of phonons and electrons in momentum space. It may offer a foundation for the study of 1D physics. Here, we investigated Ta2M3Te5 nanoflakes' anisotropic characteristics. EDS, XRD, TEM, and Raman were used to characterize the materials after they had been synthesized using chemical vapor transport. Using theoretical calculations and ultra-low frequency Raman spectroscopy, angle-dependent phonon vibrations have been investigated. The electrical transport properties of nanodevices made from a few atomic layers were studied. |
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