Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Y68: FerroicsFocus Recordings Available
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Sponsoring Units: DMP Chair: Xuejing Wang, Purdue University Room: Hyatt Regency Hotel -Hyde Park B |
Friday, March 18, 2022 8:00AM - 8:36AM |
Y68.00001: Electrical control of magnetism in 2D magnetic semiconductors Invited Speaker: Goki Eda
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Friday, March 18, 2022 8:36AM - 9:12AM |
Y68.00002: 2D ferroelectrics and their unique properties enabled by the vdW gap Invited Speaker: Nina Balke
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Friday, March 18, 2022 9:12AM - 9:24AM |
Y68.00003: Efficient control of 2D magnetism Cheng Gong, Ti Xie, Shanchuan Liang Magnetism, one of the most fundamental physical properties, has revolutionized significant technologies such as data storage and biomedical imaging, and continues to bring forth new phenomena in emerging materials of reduced dimensionalities. The recently discovered magnetic two-dimensional (2D) van der Waals materials provide ideal platforms to enable the atomic-thin, flexible, lightweight magneto-optical and magnetoelectric devices. Though many have hoped that the ultra-thinness of 2D magnets should allow an efficient control of magnetism, the state-of-the-art has not achieved notable breakthroughs to this end. In this talk, I will discuss the challenges and potential strategies for the efficient control of 2D magnetism. |
Friday, March 18, 2022 9:24AM - 9:36AM |
Y68.00004: Searching for Multiferroic Coupling in Stacked Chalcophosphate Heterostructures Patrick W Krantz, Kevin M Ryan, Eric Qian, Abishek K Iyer, Matthew M Cheng, Yea-Shine Lee, Vinayak P Dravid, Mercouri G Kanatzidis, Venkat Chandrasekhar We report on our progress in the device design and fabrication of van der Waals heterostructures that exhibit magnetoelectric coupling detectable in transport measurements. To find suitable materials with magnetic or ferroelectric ordering, we draw from the chalcophosphate chemical family grown via reactive flux methods. These materials are desirable because of their wealth of material properties1 and ease of mechanical exfoliation2. However, direct transport measurements on thin films of these materials can be challenging because they are often Mott or charge-transfer insulators3. To overcome this hurdle, we focus on a three layer geometry comprised of an ferroelectrically ordered material, a spin-orbit coupled conductor, and a magnetically ordered material, with the goal of coupling the ferroelectric and magnetic orders in the conducting behavior of the full stack. Construction of the stack on our home-built stacking stage, material characterization, and the quality of the intefaces in the devices are discussed, as are transport measurements looking for signatures of the aforementioned magnetoelectric coupling. |
Friday, March 18, 2022 9:36AM - 9:48AM |
Y68.00005: Using the nonlinearity in 2D ferroelectrics to overcome voltage-time dilemma Nikhil Sivadas, Panchapakesan Ganesh, Peter Doak Using first-principles calculations and group-theoretical methods, we study the origin and stabilization of ferrielectricity (FiE) in CuInP2Se6. We find that the polar distortions of metal atoms create most of the polarization in the FiE phase. Surprisingly, the stabilization of the FiE phase comes from an anharmonic coupling between the polar mode and a fully symmetric Raman-active mode comprising primarily of the Se atoms. This coupling is large, and the degree of anharmonicity is comparable to improper ferroelectrics. Thus, the origin of polarization is different from the factors that stabilizes the FiE phase in CuInP2Se6, unlike conventional ferroelectrics. Our results open up possibilities for dynamical control of the single-step ferroelectric switching barrier by directly tuning the Raman-active mode. These finding has important implications not only for designing next-generation microelectronic devices that can overcome the voltage-time dilemma but also in understanding the emergent responses in these materials. |
Friday, March 18, 2022 9:48AM - 10:00AM |
Y68.00006: Nanoscale strain in 2D materials from coupled structural phase transformations in BiFeO3 Carla L Watson, Arfan Sewaket, Tara Pena, Stephen M Wu 2D materials may be coupled to thin films of multiphase BiFeO3 (BFO), where electric-field induced transformations between the BFO rhombohedral (R) and tetragonal (T) structural phases can generate a large amount of strain in a coupled 2D system. Therefore, this platform allows for dynamic, high magnitude, electrically gateable strain to be generated in 2D materials that is robust to low temperatures. Here, we show that 1T’-MoTe2 and 2H-MoS2 can be coupled to strain induced by BFO structural phase transformations. Thin film BiFeO3/La0.7Sr0.3MnO3 heterostructures are grown on LaAlO3 substrates to stabilize the mixed phase growth, and TMDC materials or van der Waals heterostructures are transferred onto the oxide thin film surface. Conductive atomic force microscopy (C-AFM) is used for application of out-of-plane electric field onto individual flakes. We find that TMDC flake thickness impacts adhesion and conformality to structural transformations in BFO: 1T’-MoTe2 is fully conformal to C-AFM induced structural changes in BFO when flake thicknesses are below 3 nm. We demonstrate that bare and hBN-capped monolayer MoS2 can be strained with BFO, where photoluminescence spectroscopy on MoS2 shows variations in strain that are correlated with C-AFM induced structural transformations. |
Friday, March 18, 2022 10:00AM - 10:12AM |
Y68.00007: First-principles calculations of tunable magnetic and excitonic effects in a 2D magnetic semiconductor Kaichen Xie, Shivesh Sivakumar, Ting Cao In two-dimensional (2D) van der Waals (vdW) magnetic semiconductors, magnetic coupling between neighboring layers adds an entirely new degree of freedom to the tunable interlayer coupling, making their optical properties tunable by changing the underlying magnetism. As a 2D vdW magnetic semiconductor, layered CrSBr is ferromagnetic within each layer, and antiferromagnetically coupled between neighboring layers. In this talk, using first-principles density functional theory (DFT) and GW Bethe-Salpeter equation (GW-BSE) calculations, we demonstrate that the 2D magneto-excitons in this material hold distinct features from those in CrI3. By tuning the external magnetic field and using other control knobs, the magnetic order in layered CrSBr is switchable, which results in drastically modified excitonic transitions revealed by GW-BSE calculations. We further connect our theory and calculations to experimental observations. |
Friday, March 18, 2022 10:12AM - 10:24AM |
Y68.00008: Electrical Engineering of Phononic and Photonic Emissions in 2D Heterostructures Viviane Z. Costa, Wei Li, Cheng Gong Two-dimensional (2D) heterostructures, owing to their rich electronic, optical, and vibrational properties, unlock great possibilities towards designing ultra-compact optoelectronic, electromechanical, and optomechanical devices. To date, most of the work has focused on the intrinsic phononic and photonic properties of 2D heterostructures and utilized layer engineering to modify their properties. The effective couplings between external electrical means and the inherent optical and vibrational properties are highly desirable due to the rich fundamental physics and practical significance towards electrically operational devices, yet have not been achieved thus far. Through the systematic study of phononic and photonic emissions of 2D semiconductors interfacing with functional electronic materials, we report a sensitive dependence of the phonon modes and optical emissions with externally applied voltages. The crystal fields of 2D semiconductors are shown to be substantially altered by voltages, leading to strong coupling between external electrical means and inherent phononic and photonic emissions. Our work could pave practical avenues towards the further development of atomically thin optoelectronic and electromechanical devices. |
Friday, March 18, 2022 10:24AM - 10:36AM |
Y68.00009: First-principles study of photocatalytic CO2 reduction reactions on a 2D ferroelectric surface Mo Li, Joshua A Young The importance of reducing CO2 into value-added products is continuously increasing due to the severe outcomes of global warming. Since CO2 is a highly stable and chemically inert molecule, the reduction reaction requires catalysts that have superior selectivity and efficiency; 2D ferroelectric materials (monolayer thick compounds with a spontaneous switchable electric polarization) are coming into sight as promising candidates. 2D materials are intensively studied due to their high surface-to-volume ratio and abundant reactive sites, while the controllable and switchable polarization in 2D ferroelectric materials is a way to overcome the Sabatier Principle by changing the surface reactivity. In this study, Density Functional Theory was used to investigate the ferroelectric properties in a family of 2D MXene materials. We then selected Y2CO2, a member with the photocatalytic ability and ferroelectric properties, as the catalyst, and calculated energies and pathways of CO2 reduction reactions on its surface. Three reduction pathways leading to different C1 products (CO, formic acid, and methanol) were examined on the Y2CO2 surface. By tuning the direction of electrical polarization, we can control the stability of different intermediates and the selectivity of different products. |
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