Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session E15: 2D Materials (Semiconductors) -- MagnetismFocus
|
Hide Abstracts |
Sponsoring Units: DMP GMAG DCOMP Chair: Wenzhuo Wu, Purdue University Room: BCEC 154 |
Tuesday, March 5, 2019 8:00AM - 8:12AM |
E15.00001: Tunneling through Charge transfer heterostructure of CrI3 Tula Paudel, Evgeny Y Tsymbal Two dimensional ferromagnetic insulator CrI3 have attracted a lot of attention because of its interesting properties including tunneling magnetoresistance in a Van der Waals heterostructure. Using the first-principles methods, we calculate the spin-dependent transport through a CrI3-based tunnel junction and find that the tunneling current is 100% spin polarized. In zero bias regime, switching between the ferromagnetic and antiferromagnetic configurations of CrI3 leads to the tunneling magnetoresistance of 9800%. The transmission is mediated by the states located at the k-points away from the high symmetry points in the Brillouin zone and modulated by the distribution of the k-dependent decay states in the barrier. When biased, both the spin polarization and tunneling magnetoresistance are enhanced. This behavior persists even when the CrI3 barrier is as thin as two monolayers. Our calculations open up the possibility achieving 100% spin polarized current using conventional metallic electrodes, thereby broadening design space beyond 2D Van der Walls heterostructures. |
Tuesday, March 5, 2019 8:12AM - 8:24AM |
E15.00002: Interplay between interlayer exchange and stacking in CrX3 (X = Cl, Br, I) Claudia Cardoso, David Soriano, Joaquin Fernandez-Rossier The study of few-layer crystals with ferromagnetic (FM) order is a natural follow-up of the recent discovery of FM order in stand alone 2D crystals. And as a result, the study of the structural and magnetic interlayer interactions. Here we address the case of CrX3 (X =Cl,Br,I). All of them display FM order within the layers but have different interlayer interactions. The interlayer exchange in bulk CrCl3 is antiferromagnetic (AFM), whereas for CrBr3 and CrI3 is FM. In contrast, few-layers CrBr3 and CrI3 present an AFM interlayer coupling. [1] Moreover, the bulk systems undergo a crystallographic phase transitions with temperature and there is evidence of an strong interplay between the crystallographic and magnetic degrees of freedom, both for the bulk and the few layer systems. [2] In this study, we address the interplay between stacking and interlayer exchange coupling for CrX3 2D crystals using first-principles calculations and an effective interlayer coupling model. Our results shed light on the magnetic behavior of the CrX3 bulk and 2D crystals. |
Tuesday, March 5, 2019 8:24AM - 8:36AM |
E15.00003: Probing interlayer magnetism and magnons in two-dimensional chromium trihalides Bowen Yang, Hyun Ho Kim, George Nichols, Francois Sfigakis, Chenghe Li, Shangjie Tian, David Cory, Guoxing Miao, Hechang Lei, Adam Tsen We study CrX3 (X =I, Br, Cl) in the atomically thin limit by incorporating them in vertical tunnel junctions with graphene electrodes. In this device geometry, we are able to characterize the interlayer magnetic coupling, tunnel magnetoresistance, magnetic anisotropy, as well as magnon excitations. I will discuss the results of these studies and show how the magnetic properties of 2D CrX3 are modified when changing the halogen atom. |
Tuesday, March 5, 2019 8:36AM - 8:48AM |
E15.00004: Raman spectroscopy studies of spin waves in two-dimensional CrI3 Wencan Jin, Hyun Ho Kim, Zhipeng Ye, Siwen Li, Pouyan Rezaie, Fabian S Diaz, Saad Siddiq, Eric S Wauer, Bowen Yang, Chenghe Li, Shangjie Tian, Kai Sun, Hechang Lei, Adam W Tsen, Rui He, Liuyan Zhao The long-range magnetic order in the two-dimensional (2D) limit at finite temperatures has recently been demonstrated in a honeycomb Ising ferromagnet CrI3. It has triggered tremendous interest in 2D magnet-based applications. To achieve a complete understanding of the 2D magnetic phase, a direct measurement of the magnetic excitations, i.e., spin waves, or magnons, is pressingly in need. In this talk, we will present the experimental evidence of spin waves in the 2D honeycomb ferromagnet, CrI3. Using polarized micro-Raman spectroscopy, we have identified two branches of zero-momentum spin waves in 2D CrI3 with exceptionally high frequencies in the THz range, as compared to those of the conventional ferromagnets. By tracking the layer thickness dependence of both spin waves, we further show that both are surface magnons, and their lifetimes remain an order of magnitude longer than their temporal period down to the monolayer limit. |
Tuesday, March 5, 2019 8:48AM - 9:00AM |
E15.00005: Electrical control of magnetism in 2D CrI3 Kin Fai Mak, Shengwei Jiang, Lizhong Li, Zefang Wang, Jie Shan Controlling magnetism by purely electrical means is a key challenge to better information technology. The recent discovery of two-dimensional van der Waals magnets has opened a new door for electrical control of magnetism at the nanometer scale through the van der Waals heterostructure device platform. We demonstrate control of magnetism in monolayer and bilayer CrI3 by application of pure electric field or electrostatic doping. In bilayer CrI3, we observe a large linear magnetoelectric effect, whose sign depends on the interlayer antiferromagnetic order. In monolayer CrI3, doping significantly modifies the saturation magnetization, coercive force and Curie temperature, showing strengthened (weakened) magnetic order with hole (electron) doping. Remarkably, in bilayer CrI3 doping drastically changes the interlayer magnetic order, causing a transition from an antiferromagnetic ground state in the pristine form to a ferromagnetic ground state. These results reveal the strong electric field and doping-dependent interlayer exchange coupling, which enables us to achieve the robust and reversible switching of magnetization in bilayer CrI3 by small gate voltages. |
Tuesday, March 5, 2019 9:00AM - 9:12AM |
E15.00006: ABSTRACT WITHDRAWN
|
Tuesday, March 5, 2019 9:12AM - 9:24AM |
E15.00007: WITHDRAWN ABSTRACT
|
Tuesday, March 5, 2019 9:24AM - 9:36AM |
E15.00008: Magneto-optical Kerr effect in two-dimensional diluted magnetic transition metal dichalcogenide semiconductors Gonçalo Catarina, Joaquin Fernandez-Rossier In this talk, I will present a theory to model the Kerr angle for two-dimensional transition metal dichalcogenide semiconductors, such as MoS2, doped with a small density of magnetic atoms. The model Hamiltonian describes the band carriers within the effective gapped Dirac theory, accounting for spin-orbit and spin-valley coupling [1]. The magnetic impurities are described within a mean-field virtual crystal approximation, leading to a band-dependent spin splitting of the spectrum [2]. We find that the transverse optical susceptibility is non-zero, leading to a finite Kerr angle, when the exchange-induced splitting in the valence and conduction bands are different. We consider the case when there are no free carriers in the bands, as well as the n-doped and p-doped regimes. |
Tuesday, March 5, 2019 9:36AM - 9:48AM |
E15.00009: Magnetism and Distortions in Transition-Metal Dioxide Layers:
On the Quest for Intrinsic Magnetic Semiconductor Layers Faustino Aguilera-Granja, Andres Ayuela Future nanoscale technological applications in spintronics require research on two dimensional materials with combined semiconductor and magnetic properties. We investigate transition metal dioxides in the form of layers, and report on the structural and electronic properties of selected late transition metal d-elements. With half-filled d states, the MnO2 and TcO2 layers are magnetic semiconductors, and for side d-elements the CrO2 and FeO2 layers become half-metals. These magnetic materials in 2D must be synthesized in order to assess their usefulness in future electronic and spintronic devices. |
(Author Not Attending)
|
E15.00010: Diversified Magnetoelectric Coupling in 2D Multiferroic Materials Qing Yang, Menghao Wu Multiferroic materials with coupled magnetism and ferroelectricity, even though scarcely exist in nature, are highly desirable for efficient “electric writing + magnetic reading”. Currently, the polarization and magnetization of traditional multiferroics with strong magnetoelectric coupling are all too weak for practical applications. Here we show first-principles evidences that strong magnetoelectrics can be realized in a series of 2D multiferroics: in some intercalated bilayer systems, their “mobile” magnetism can be controlled by ferroelectric switching upon external electric field, exhibiting either “on” state with spin-selective and highly p-doped channels, or “off” state insulating for both spin and electron transport, which renders efficient electrical writing and magnetic reading; vertical polarization can be maintained against depolarizing field, rendering high-density data storage possible. In some 2D systems, the magnetization can be switched by 90 or even 180 degree upon ferroelectric switching. |
Tuesday, March 5, 2019 10:00AM - 10:12AM |
E15.00011: Negative Parabolic Magnetoresistance due to Electron-Electron Interactions in a Disordered 2D Electron Gas in InSe Kasun Premasiri, Rajesh Kumar, Raman Sankar, Fangcheng Chou, Xuan Gao Magnetotransport measurements serve as a multifarious tool in understanding various phenomena involved in electron transport, among which the prevalence of the electron–electron interaction (EEI) represents a key aspect with its unique magnetoresistance (MR) signatures. Semiconductor–heterostructure–based, two–dimensional electron gases (2DEGs) have been extensively studied to extract information about the EEI. Two–dimensional (2D) materials may provide more insight into the EEI, possessing an array of materials with extreme versatility in electronic properties. We report negative parabolic MR due to the EEI in a 2DEG formed in InSe, which is a 2D monochalcogenide semiconductor. In this system, we study the EEI in the regime of ωcτ<1, which is relatively unexplored. A logarithmic relationship between the EEI and the temperature is observed confirming the contribution from the EEI to the MR. We also compare the strength of the observed EEI with other conventional systems such as Si metal–oxide semiconductor field–effect transistors and GaAs quantum wells. |
Tuesday, March 5, 2019 10:12AM - 10:24AM |
E15.00012: Ferromagnetism created from non-ferromagnetic vdW heterostructures Cheng Gong, Peiyao Zhang, Tenzin Norden, Quanwei Li, Zhen Guo, Apoorva Chaturvedi, Arman Najafi, Shoufeng Lan, Xiaoze Liu, Yuan Wang, Hao Zeng, Hua Zhang, Athos Petrou, Xiang Zhang Intrinsic long-range ferromagnetic order has recently been discovered in two-dimensional atomic crystals. However, the prospect of 2D magnets remains largely hindered by the scarcity of 2D ferromagnets with limited diversity in magnetic attributes. In this context, creative ways to bring forth ferromagnetism from non-ferromagnetic 2D materials are attractive and profitable for both fundamental physics and device applications. In this talk, I will show you the possibility of such creation based on our magneto-optical study of vdW heterostructures and discuss the underlying material physics. Our work paves the new path to harvest 2D ferromagnetism. |
Tuesday, March 5, 2019 10:24AM - 10:36AM |
E15.00013: Electrically tunable magnon bands in two-dimensional magnets Mohammad Mushfiqur Rahman, Avinash Rustagi, Yong Chen, Pramey Upadhyaya Magnons, namely quanta of spin waves-coherent excitations of magnetically ordered medium-are considered as promising carriers of spin information for classical [Nat. Phys. 11, 453 (2015)] and quantum [npj Quantum Info. 3, 28 (2017)] information processing. For these applications, the ability to electrically reconfigure the bandstructure of magnons, can open novel opportunities to create dynamic magnon crystals and multifunctional high frequency, logic and quantum devices [Journal of Phys. D: Appl. Phys.50, 24 (2017)]. In this work, we propose a novel platform to realize electrically tunable magnon bands, namely recently discovered two-dimensional (2-D) magnets [Nature 546, 270(2017)]. For this purpose, we utilize the efficient electrical control of spin-spin interactions within bilayer Chromium Iodide [Nature Mat. 17, 406 (2018)] to numerically demonstrate electrically controlled sub-Terahertz magnons. This study opens the possibility of using van der Waal magnets and their heterostructures for high frequency magnon spintronics applications. |
Tuesday, March 5, 2019 10:36AM - 10:48AM |
E15.00014: Raman phonon spectra from CrI3 atomic layers Rui He, Zhipeng Ye, Gaihua Ye, Eric S Wauer, Fabian S Diaz, David Tauzin, Hyun Ho Kim, Bowen Yang, Adam Tsen, Hua Wang, Xiaofeng Qian, Wencan Jin, Liuyan Zhao CrI3 has recently been demonstrated to be an Ising ferromagnet whose magnetization retains even in a single monolayer below Curie temperature. Here we report our recent Raman studies on bulk and monolayer/few-layer CrI3. Temperature-dependent Raman studies are performed to scrutinize structural phase transition and magnetic phase transition. We determine the symmetries of the phonon modes using polarized Raman spectroscopy and first-principles theoretical calculations. Our results show that Raman selection rule no longer holds in degraded CrI3 samples. |
Tuesday, March 5, 2019 10:48AM - 11:00AM |
E15.00015: Giant excitonic and magneto-optical responses in two-dimensional ferromagnets Meng Wu, Zhenglu Li, Ting Cao, Steven G. Louie The magneto-optical (MO) effects, such as the magneto-optical Kerr effect (MOKE) and the Faraday effect, have been intensively investigated in a variety of magnetic materials serving as a highly sensitive probe for electronic and magnetic properties. Recent experiments using MOKE have discovered a few two-dimensional (2D) magnets, and demonstrated their rich magnetic behaviors. In particular, a giant Kerr response has been measured in monolayer and few-layer CrI3. However, by far, the microscopic origin of such MO signals is still unknown, because the essential spin-orbit coupling and excitonic effects are beyond the capability of existing first-principles methods. With newly developed GW and GW-BSE methods, we show that the exceedingly large optical and MO responses in ferromagnetic monolayer CrI3 arise from the strongly bound exciton states consisting of spin-polarized electron-hole states. With a realistic experimental setup, we find that the substrate configuration and excitation frequency strongly shape the MO signals. Our first-principles results are in good agreement with recent experiments on CrI3. |
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