Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session K55: Electronic, Optical and Spin Dependent Properties in 2D SystemsRecordings Available
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Sponsoring Units: DCMP Chair: Bellave Shivaram, University of Virginia Room: Hyatt Regency Hotel -Adler |
Tuesday, March 15, 2022 3:00PM - 3:12PM |
K55.00001: Shubnikov-de Haas oscillations in sub-terahertz regime Andrei Pimenov, Jan Gospodaric, Maxim Savchenko, Alexey Shuvaev, A. A Bykov, A. K Bakarov, Z. D Kvon, Ivan A Dmitriev We carry out sub-terahertz magneto-transmission experiments in GaAs quantum wells. In addition to cyclotron resonance, several types of quantum oscillations can be observed: (i) AC Shubnikov-de Haas (SdH) oscillations in dynamic conductivity and (ii) MIRO-like quantum oscillations in transmission in low magnetic fields and high temperatures. The static quantum properties, SdH in DC resistance and MIRO (microwave-induced resistance oscillations), are measured in the same conditions. SdH at high frequencies deviate substantially from similar experiments in the static regime. The most important new effect is the phase beating at a rate equal to an integer times the cyclotron resonance (CR) frequency. |
Tuesday, March 15, 2022 3:12PM - 3:24PM |
K55.00002: Micrometer-scale single-crystalline borophene on a square-lattice Cu(100) surface Rongting Wu, Stephen Eltinge, Ilya K Drozdov, Adrian Gozar, Percy Zahl, Jerzy T Sadowski, Sohrab Ismail-Beigi, Ivan Božović Borophene, a crystalline monolayer boron sheet, is a new two-dimensional (2D) quantum material, predicted to feature tunable structure, intriguing physics and to find applications in flexible electronics, energy storage, and catalysis. Nanoscale borophene flakes have been synthesized on noble-metal surfaces, but for device fabrication, one needs large single-crystal domains. We report the synthesis of borophene on a square lattice Cu(100) surface and show that incommensurate coordinations could reduce the borophene-substrate interactions and alter the borophene structures in interesting ways. Micrometer-scale single-crystal domains can form as isolated faceted islands or merge together to achieve full monolayer coverage. We have discovered a new crystal structure of borophene, with ten boron atoms and two hexagonal vacancies in the unit cell. First-principle calculations indicate that charge transfer rather than covalent bonding binds 2D boron to the copper surface, and confirm its integrity and uniformity. The electronic band structure features multiple anisotropic tilted Dirac cones, heralding emergent quantum fermions. |
Tuesday, March 15, 2022 3:24PM - 3:36PM |
K55.00003: Thermally-driven phase transitions on silicene, germanene, and stanene John M Davis, Salvador Barraza-Lopez Silicene, germanene, and stanene are degenerate depending which atom (A or B) buckles up. Finite-temperature phonon dispersion curves, coordination, and other physical properties as obtained from ab initio molecular dynamics calculations at finite temperatures for these materials will be shown. Silicene is seen to turn amorphous at a certain temperature. |
Tuesday, March 15, 2022 3:36PM - 3:48PM |
K55.00004: On the structural evolution of low-dimensional germanium phases forming 2D germanene on Ag(111) studied by XPS and XPD Lukas Kesper, Marie Schmitz, Julian A Hochhaus, Malte G Schulte, Ulf Berges, Carsten Westphal In the last decade, research on 2D-materials has expanded massively due to the popularity of graphene. Although the chemical engineering of two-dimensional elemental materials, as well as heterostructures has been extensively pursued, the fundamental understanding of the synthesis of 2D-materials is not yet complete. Structural parameters, such as the buckling or substrate bonding of a 2D-material directly affect its electronic characteristics, like the famous Dirac-behavior. |
Tuesday, March 15, 2022 3:48PM - 4:00PM |
K55.00005: Nanoscale polarization anisotropy in black phosphorus Prakriti P Joshi, Ruiyu Li, Joseph L Spellberg, Sarah B King Black phosphorus (BP) supports anisotropic charge, phonon, plasmonic, and polaritonic behavior, making it well-suited for the development of polarization-dependent photodetectors and thermoelectrics, as well as directional waveguides and light emitters. However, BP is also rich in nanoscale morphologies such as edges, strain, and wrinkles, which strongly modulate its electronic properties. Determining the interplay of morphology-mediated and intrinsic electronic behavior requires 10-100 nm-scale resolution, beyond the reach of conventional optical microscopy (> 200 nm), and a large field of view, beyond that of TEM and STM (< 20 nm). We use polarization-dependent photoemission electron microscopy (PEEM) to probe the morphology-electronic structure relationship of few-layer BP with 54 nm resolution. At the edges of BP we find the polarization dichroism is phase-shifted by 10 - 20○ with respect to the armchair direction of the bulk lattice in flakes. This suggests an edge modification to optical transitions and the symmetries of the conduction and valence bands, which may manifest from edge reconstructions and interlayer effects, enabling selective excitation and manipulation of black phosphorus edge states. |
Tuesday, March 15, 2022 4:00PM - 4:12PM |
K55.00006: Ferroelectricity in Two-Dimensional Antimony Oxides Romakanta Bhattarai, Xiao Shen Three different polymorphs of antimony (IV) oxide, namely, γ-Sb2O4, δ-Sb2O4, and ε-Sb2O4, are predicted by using the evolutionary algorithm combined with the first-principles density functional theory calculations. The γ-Sb2O4 and δ-Sb2O4 phases are layered, which makes them the first two-dimensional (2D) materials of this stoichiometry. Out-of-plane ferroelectricity is predicted in the 2D γ-Sb2O4 phase, while in-plane ferroelectricity is predicted in the 2D δ-Sb2O4 phase. Meanwhile, the ε-Sb2O4 phase is not layered. All three phases are predicted to be indirect bandgap semiconductors, with the gap ranging from 2.25 eV to 5.51 eV, depending upon the Sb-O bonding configurations and their dimensionalities. Also, the anisotropy in optical properties is observed, which is closely related to their anisotropic crystal structures and the unique bonding mechanisms between Sb and O atoms. Analysis of Raman spectra along with the vibrational modes is also performed to pave the way for the experimental investigation of the predicted structures. The existence of both in-plane and out-of-plane 2D ferroelectricity and the large band gaps are notable features of these new Sb2O4 phases, which may be of interest for potential applications in electronics and optoelectronics. |
Tuesday, March 15, 2022 4:12PM - 4:24PM |
K55.00007: Ab initio modeling of lead-free perovskite-derived 2D Cs3Bi2I9 Srihari M Kastuar, Chinedu E Ekuma, Zhong-Li Liu In recent years, organic-inorganic mixed halide perovskites have been of utmost importance for renewable energy and information technology due to their remarkable properties. But the toxicity of lead and instability of the organic component has limited the potential applications of such materials. The environmentally friendly Pb-free all inorganic two-dimensional (2D) perovskite derived material of the family of Cs3Bi2I9 (CBI) are promising to overcome these limitations. In this work, we have been modeling 2D CBI using Density Functional Theory to study its electronic structure, elastic and mechanical stability, and Raman spectrum. We also propose to use high-throughput computational approaches assisted by materials informatics, machine learning (ML) models, and first-principles computational modelling to develop a comprehensive understanding of the emerging properties, such as mechanical, optoelectronic, and transport properties of 2D CBI family. The mechanical stability (temperature-dependent) will be studied using the ElasTool toolkit, which is highly efficient for predicting the mechanical properties of materials. Using high-throughput computational modelling and ML models, we will screen the CBI family to determine those with interesting properties for further study using first-principle techniques. |
Tuesday, March 15, 2022 4:24PM - 4:36PM |
K55.00008: Importance of the Organic Component in the Layered Perovskite Semiconductors Yulia Lekina, Benny Febriansyah, Jiaxu Yan, Xiaofeng Fan, John Hanna, zexiang shen As next-generation semiconductors, hybrid perovskites with tailorable optoelectronic properties are critical for applications. In comparison to the3D counterparts, 2D perovskites exhibit improved moisture stability, the naturally formed quantum-well structure, and extended chemical engineering possibilities. Tunability lies on several factors: variable compositions, crystal structure where the spatial arrangement of halide octahedra has a great influence on the assembly behavior and materials properties; the organic molecules whose main function is to stabilize the perovskite materials through their interactions with the inorganic components. The optical properties are mainly contributed by the inorganic sublattice, while the importance of the organic component is more complex and requires further investigation. In this work, we discuss how the properties of 2D perovskites are dependent on the nature of the organic cations. By utilizing optical and vibrational spectroscopy in a wide temperature and pressure range, we demonstrate how various modifications of the organic groups bring up specific phenomena, such as disorder, in-plane anisotropy, response to extreme pressure. |
Tuesday, March 15, 2022 4:36PM - 4:48PM |
K55.00009: Anomalous Hall Effect in Ultrathin Crystalline Strontium Ruthenate Membranes Patrick Blah, Edouard Lesne, Martin Lee, Marco Bonura, Stefano Gariglio, Ana Monteiro, Dmytro Afanasiev, Thierry C van Thiel, Mattias Matthiesen, Jorrit R Hortensius, Ulderico Filippozzi, Yingkai Huang, Herre S.J. van der Zant, Peter G Steeneken, Andrea Caviglia
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Tuesday, March 15, 2022 4:48PM - 5:00PM |
K55.00010: Emergent continuous symmetry in anisotropic flexible two-dimensional materials Valentin Kachorovskii We develop the theory of anomalous elasticity in two-dimensional flexible materials with orthorhombic crystal symmetry. Remarkably, in the universal region, where characteristic length scales are larger than the rather small Ginzburg scale ~10nm, these materials possess an infinite set of flat phases which are connected by emergent continuous symmetry. This hidden symmetry leads to the formation of a stable line of fixed points corresponding to different phases. The same symmetry also enforces power law scaling with momentum of the anisotropic bending rigidity and Young's modulus, controlled by a single universal exponent - the very same along the whole line of fixed points. These anisotropic flat phases are uniquely labeled by the ratio of absolute Poisson's ratios. We apply our theory to monolayer black phosphorus (phosphorene). |
Tuesday, March 15, 2022 5:00PM - 5:12PM |
K55.00011: Dynamical correlation of interlayer shearing and magnetism in van der Waals antiferromagnets Faran Zhou, Kyle Hwangbo, Qi Zhang, Jiawei Zhang, Chong Wang, Qianni Jiang, Alfred Zong, Yifan Su, Marc Zajac, Donald A Walko, Richard D Schaller, Jiun-Haw Chu, Nuh Gedik, Di Xiao, Xiaodong Xu, Haidan Wen The coupling of multiple degrees of freedom in quantum materials underlies their unique electronic, spintronic, and optical properties. Distinct spin-lattice coupling is discovered in van der Waals antiferromagnets (e.g. FePS3 and NiPS3) when they are driven to states far from equilibrium. Using ultrafast x-ray diffraction and optical linear dichroism measurements, we reveal that the interlayer shearing, rather than intralayer lattice distortion, exhibits critical slowing down at the Neel temperature. The dynamics of interlayer shearing follow the recovery of the antiferromagnetic order but decouples from lattice cooling. The correlated dynamics of the interlayer shearing and the antiferromagnetic order can be understood within the framework of the Ginzburg-Landau theory, in which the specific form of the spin-lattice coupling is dictated by the zigzag magnetic symmetry, a phenomenon that is absent in three-dimensional quantum materials. The discovery of the pivotal role of interlayer shearing in stabilizing the magnetic order opens up opportunities in controlling magnetism via engineering layered heterostructures for new functionalities. |
Tuesday, March 15, 2022 5:12PM - 5:24PM |
K55.00012: Momentum-space Spin Anti-vortex and Spin Transport in Monolayer Pb Kai-Jie Yang Non-trivial momentum-space spin texture of electrons can be induced by spin-orbit coupling and underpins various spin transport phenomena, such as current-induced spin polarization and spin Hall effect. In this work, we find a non-trivial spin texture, spin anti-vortex, can appear at certain momenta on the $\Gamma-\text K$ line in 2D monolayer Pb on top of SiC. Different from spin vortex due to the band degeneracy in the Rashba model, the existence of this spin anti-vortex is guaranteed by Poincare-Hopf theorem and thus topologically stable. Accompanied with this spin anti-vortex, a Lifshtiz transition of Fermi surfaces occur at certain momenta on the K-M line, and both phenomena are originated from the anti-crossing between the $j=1/2$ and $j=3/2$ bands. A rapid variation of the response coefficients for both the current-induced spin polarization and spin Hall conductivity is found when the Fermi energy is tuned around the spin anti-vortex. Our work demonstrates the monolayer Pb as a potentially appealing platform for spintronic applications. |
Tuesday, March 15, 2022 5:24PM - 5:36PM |
K55.00013: Materials where crystal structure and electronic structure have different quasi-dimensionality Sinisa Coh We theoretically study materials, such as LaTe3, in which the effective dimensionality of the crystal structure is quasi-two-dimensional while the electronic structure is quasi-one-dimensional. We show this by using a basis of electronic states that are maximally localized both in space and time. Unlike maximally localized Wannier functions, these orbitals have the property that their spread in space is minimally changing over time. We find that in such basis, relevant Te p-like electron orbitals evolve along one-dimensional chains within the LaTe3 plane (other p-like orbitals disperse in the perpendicular direction). We also find large, but less pronounced, quasi-one-dimensionality of electronic structure in NbS3. Interestingly, in NbS3 p-like orbitals on S tend to evolve along one-dimensional chains perpendicular to the ones formed by d-like Nb orbitals. We related these findings to the charge density wave state in both LaTe3 and NbS3. When we apply our approach to graphene, black phosphorene, and MoS2 we find that all three have very isotropic quasi-two-dimensional electronic structures (unlike LaTe3 and NbS3). |
Tuesday, March 15, 2022 5:36PM - 5:48PM |
K55.00014: Lightwave-driven tunneling spectroscopy of graphene nanoribbons Spencer E Ammerman, Vedran Jelic, Yajing Wei, Vivian N Breslin, Mohamed Hassan, Nathan Everett, Sheng Lee, Qiang Sun, Carlo Antonio Pignedoli, Pascal Ruffieux, Roman Fasel, Tyler L Cocker Novel atomic-scale electronics operating at optical frequencies require new tools that can characterize them and inform device fabrication. Lightwave-driven scanning tunneling microscopy is a promising new technique towards this purpose. By coupling free-space-propagating single-cycle terahertz transients to an atomically sharp metal tip, it achieves simultaneous sub-angstrom and sub-picosecond spatio-temporal resolution [1–7]. Here, we utilize terahertz scanning tunneling microscopy (THz-STM) and spectroscopy (THz-STS) to investigate seven-atom-wide graphene nanoribbons on an Au(111) surface and unveil highly localized wavefunctions that are inaccessible with conventional scanning tunneling microscopy [7]. Three-dimensional tomographic THz-STM imaging of the electron densities of the wavefunctions reveals a faster vertical decay of the valance band compared to the conduction band.
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