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 TT08: V: Complex Structured Materials, Including Graphene III |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Dacen Waters, University of Washington Room: Virtual Room 8 |
Tuesday, March 21, 2023 3:30PM - 3:42PM |
TT08.00001: Dynamics of thermal rippling of 2D MoSe2 membranes Songge Li, Yun-Peng Wang, Shoucong Ning, Sokrates T Pantelides, Wu Zhou, Junhao Lin Rippling is a ubiquitous structural feature of freestanding monolayer two-dimensional (2D) materials. Phenomenological theory of the thermodynamic behavior of flexible membranes predict a power law for the correlation function of the out-of-plane displacements. We have demonstrated that the ripple structure of monolayer transition-metal dichalcogenides can be reconstructed from a single-frame scanning-transmission electron-microscopy image collected at designated angles. Here we take a sequence of such images of MoSe2 and deduce the dynamics of rippling by combining the experimental images with pertinent molecular dynamics simulations based on empirical potentials. We first reconstruct the atomic-scale structures of 3D ripple distortions of suspended MoSe2 membrane from STEM images. Fourier analysis of both the reconstructed images and molecular dynamics snapshots demonstrate that the correlation function H(q) follows the scaling law H(q) ∝ q-4 fairly well. We not only provide a new tool in atomic structure reconstruction with temporal resolution, but also give the first direct evidence for the classical theory of thermal fluctuations in 2D membranes. |
Tuesday, March 21, 2023 3:42PM - 3:54PM |
TT08.00002: Theory of strain-dependent electronic structure and the valley orbital model for the monolayer transition metal dichalcogenides MX2 PRATIK K SAHU, Sashi S Satpathy The broken inversion symmetry in transition metal dichalcogenides (TMDs) such as MoS2 leads to coupled spin-valley physics, which is well described by the low-energy valley-orbital model applicable to the electronic structure near the K/K' valley points. The spin-valley physics can be modified by introducing strain into the system, which has emerged as an important tool to manipulate the electronic properties. Here, we develop a valley-orbital model for the general strain condition by adopting an approach different from earlier works, which allows us to formulate the model valid around the valley points. The form of the strain Hamiltonian, which we obtain to linear order in momentum q about the valley points, is developed by considering a tight-binding model under strain condition and validated by comparing with the density-functional theory (DFT) results. The Hamiltonian properly describes the shape change of the energy contours and the shift of the valley extrema points under a general strain condition. The total energy expression follows the appropriate form for the D3h symmetry, which is well known from the theory of elasticity. The Hamiltonian parameters are presented for a number of TMDs obtained from the DFT calculations. Our results are valuable for describing strain-dependent valley-orbital physics for this important class of materials. |
Tuesday, March 21, 2023 3:54PM - 4:06PM |
TT08.00003: Engineering photoluminescence using strain in two-dimensional transition-metal dichalcogenides ANUJ K SINGH, Kishor K Mandal, Brijesh Kumar, Lekshmi Eswaramoorthy, ANSHUMAN KUMAR
|
Tuesday, March 21, 2023 4:06PM - 4:18PM |
TT08.00004: Enhanced bulk photovoltaic effect in strained 3R-MoS2 Yu Dong, Mingmin Yang, Mao Yoshii, Sota Kitamura, Takahiro Morimoto, Naoki Ogawa, Toshiya Ideue, Yoshihiro Iwasa Bulk photovoltaic effect (BPVE) is attracting much attention due to its innate coupling with wave function geometry and potential to achieve a higher solar energy conversion efficiency. So far, BPVE has been studied in a variety of materials, such as oxide superlattices1, halide perovskites2, organics3, Weyl semimetals4 and van der Waals nanomaterials5. Meanwhile, several methods are also developed to optimize the performance of BPVE6,7. Among them, strain is a simple but effective way7 for obtaining the enhanced photovoltaic signals. In this study, we focused on the effect of strain on the bulk photovoltaic property in layered 3R-MoS2, which has a noncentrosymmetric crystal structure whose symmetries can be modified by uniaxial strain. We found the giant enhancement of the bulk photovoltaic effect in strained 3R-MoS2, which can be attributed to the emergence of the strain-induced in-plane polarization8. In the presentation, we report the detailed photovoltaic behaviors such as directional dependence, photon energy dependence, and strain dependence. Possible mechanism will also be discussed. |
Tuesday, March 21, 2023 4:18PM - 4:30PM |
TT08.00005: Enabling direct write fabrication of low dimensional micro- and nanostructures on supported and suspended substrates using custom inks and CVD synthesis Irma Kuljanishvili Low dimensional nanomaterials such as 1D or 2D systems, assembled in vertical or lateral arrangements, often lead to the enhanced properties, and new functionalities. Nanotubes, nanowires (NWs), and 2D layered structures are emerging as key building blocks for the next generation technologies. Practical implementation of such nanomaterials necessitates their successful incorporation with well-established processes for fabrication of electrical and mechanical devices. While the preparation of layered architectures usually involves multi-step fabrication processes it also relies on mask assisted fabrication techniques. Here we present methodology for controlled and selective preparation of nanostructures such as 1D ZnO NWs or 2D TMDC, in various controlled geometric assemblies, by employing direct write patterning (DWP) of custom ink precursors on supported or suspended architectures. Our two-step fabrication approach enables simple and flexible production of various architectures in a precisely controlled fashion. Location specific synthesis of materials provides access to as-grown interfaces and rapid testing of materials’ quality, crystallinity and chemical composition, etc. |
Tuesday, March 21, 2023 4:30PM - 4:42PM |
TT08.00006: New low-frequency optic phonon behaviour in single crystal incommensurate Bi-2212 Brad McNiven, James LeBlanc, G. Todd Andrews Room temperature Brillouin light scattering experiments on single crystal Bi-2212 were conducted between 0-6 cm^-1 at 532 nm through use of an ultra-high contrast Fabry-Perot interferometer. From spectra collected very close to the crystallographic c-axis, an extremely low-lying optic phonon mode was observed near 6 cm^-1 (~200 GHz), while higher angle spectra show this mode to dissipate. This behaviour is highly reminiscent of other low-lying optic phonons in Bi-2212 whose origins have been recently connected to the crystals incommensurate structure. This work opens many questions surrounding phonon behaviour in BSCCO compounds, such as their role in unconventional superconductivity via electron-phonon coupling. |
Tuesday, March 21, 2023 4:42PM - 4:54PM |
TT08.00007: Strongly correlated exciton-polarons in twisted two-dimensional heterostructures Giacomo Mazza, Adriano Amaricci In heterostructures of twisted two-dimensional semiconductors the combined effect of the moiré potential and the Coulomb interaction can support the formation of different strongly correlated phases, including charge ordered or Mott localized phases. Yet, identifying the nature of such correlated phases remains a key issue. |
Tuesday, March 21, 2023 4:54PM - 5:06PM |
TT08.00008: Giant quantum anharmonic effects in Cyclo[4n+2]carbon Davide Romanin, Matteo Calandra Cyclo[4n+2]carbons are sp-bonded carbon rings in which Hückel rule predicts a fully symmetric structure that is, however, in competition with the second order Jahn–Teller (Peierls) distortion. This picture, however, neglects the crucial role played by nuclear quantum effects. In a recent work we investigated the magnitude of nuclear quantum effects on the stability, vibrational and optical properties of cyclo[4n+2]carbons (n=1,2,3,4) in vacuum. We showed that quantum structural minimization reduces the energy separation between the different isomers and determines that the most stable one as the cumulenic phase, setting the transition from the polyyenic to the cumulenic form at n=3 (at odd with the classical structural optimization setting the transition at n=2). Moreover, the optical absorbance is completely reshaped by quantum anharmonic vibrations with redshifts ranging from 0.4 to 1.0 eV in the first excitonic absorption with respect to the static ionic picture. Our work outlines the crucial role of nuclear quantum effects in the understanding of carbon molecular systems. |
Tuesday, March 21, 2023 5:06PM - 5:18PM |
TT08.00009: Optical conductivity of semi-Dirac and pseudospin-1 models: Zitterbewegung approach Dmytro Oriekhov, Valery Gusynin We present a method to calculate the optical conductivity of semi-Dirac and pseudospin models based on the evaluation of quasiparticle velocity correlators which also describe the phenomenon of zitterbewegung. Applying this method to the semi-Dirac model with merging Dirac cones and gapped dice and Lieb lattice models we find exact analytical expressions for optical longitudinal and Hall conductivities. For the semi-Dirac model the obtained expressions allow us to analyze the role of spectrum anisotropy, van Hove singularities and Dirac cones in longitudinal conductivity. In addition, we predict signatures of topological phase transition with changing gap parameter in such a system that are manifested in dc transport at low temperatures. For the dice and Lieb lattices we emphasize the role of spectral gap, which defines frequency thresholds related to transitions to and from flat band. |
Tuesday, March 21, 2023 5:18PM - 5:30PM |
TT08.00010: Strain Tuning of Energy Transfer from 0D to 2D Burak Aslan, Esra Simsek, Abdulhay C Kara, Ahmet O Ölçer We probe the effect of mechanical strain on the non-radiative energy transfer (NRET) rate from a 0-dimensional material, CdSe/ZnS quantum dot (QD), to a 2-dimensional material, monolayer (1L) WS2. Our calculations show that the NRET rate is enhanced as the emission spectrum of CdSe/ZnS QD overlaps with the exciton resonances of 1L WS2. On that basis, the NRET rate is strongly dependent on the magnitude of strain, since applying strain shifts the exciton energies in 1L WS2. Based on the experimental results in the literature, we have computed the strain-dependent dielectric function of WS2. We calculate the NRET rate as a function of uniaxial strain and show that it can be greatly tuned by purely mechanical means. We choose WS2 among the commonly used semiconducting group-6 transition metal dichalcogenides; WSe2, MoS2, MoSe2, MoTe2 as it has the smallest A exciton linewidth at room temperature, which is relatively less sensitive to strain. Our results exemplify the use of mechanical strain as a means of shedding light on the interaction between low-dimensional material systems. We will follow up with experiments in which we will deposit quantum dots on 2D materials and perform photoluminescence spectroscopy to demonstrate the strain-engineered NRET in QDs. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit 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 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700