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Chang Y, Zhang Z, Deng L, Wu Y, Zhang X. Ferrovalley and Quantum Anomalous Hall Effect in Janus TiTeCl Monolayer. MATERIALS (BASEL, SWITZERLAND) 2024; 17:3331. [PMID: 38998413 PMCID: PMC11243056 DOI: 10.3390/ma17133331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2024] [Revised: 06/30/2024] [Accepted: 07/03/2024] [Indexed: 07/14/2024]
Abstract
Ferrovalley materials are garnering significant interest for their potential roles in advancing information processing and enhancing data storage capabilities. This study utilizes first-principles calculations to determine that the Janus monolayer TiTeCl exhibits the properties of a ferrovalley semiconductor. This material demonstrates valley polarization with a notable valley splitting of 80 meV. Additionally, the Berry curvature has been computed across the first Brillouin zone of the monolayer TiTeCl. The research also highlights that topological phase transitions ranging from ferrovalley and half-valley metals to quantum anomalous Hall effect states can occur in monolayer TiTeCl under compressive strains ranging from -1% to 0%. Throughout these strain changes, monolayer TiTeCl maintains its ferromagnetic coupling. These characteristics make monolayer TiTeCl a promising candidate for the development of new valleytronic and topological devices.
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Affiliation(s)
- Yufang Chang
- Public Basic Department, Shenyang Conservatory of Music, Shenyang 110818, China;
| | - Zhijun Zhang
- School of Electrical and Automation Engineering, Liaoning Institute of Science and Technology, Benxi 117004, China;
| | - Li Deng
- School of Material Science and Engineering, Northeastern University, Shenyang 110819, China; (L.D.); (Y.W.)
| | - Yanzhao Wu
- School of Material Science and Engineering, Northeastern University, Shenyang 110819, China; (L.D.); (Y.W.)
| | - Xianmin Zhang
- School of Material Science and Engineering, Northeastern University, Shenyang 110819, China; (L.D.); (Y.W.)
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2
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Liu Z, Zhou B, Wang X. Two-dimensional multiferroic RuClF/AgBiP 2S 6 van der Waals heterostructures with valley splitting properties and controllable magnetic anisotropy. Phys Chem Chem Phys 2024; 26:17869-17881. [PMID: 38887794 DOI: 10.1039/d4cp01059k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Abstract
The investigation of new properties in two-dimensional (2D) multiferroic heterostructures is significant. In this work, the electronic properties and magnetic anisotropy energies (MAEs) of 2D multiferroic RuClF/AgBiP2S6 van der Waals (vdW) heterostructures are systematically studied by first principles calculations based on density functional theory (DFT). The Hubbard on-site Coulomb parameter (U) of Ru atoms is necessary to account for the strong correlation among the three-dimensional electrons of Ru. RuClF/AgBiP2S6 heterostructures in different polarizations (RuClF/AgBiP2S6-P↑ and RuClF/AgBiP2S6-P↓) are ferromagnetic semiconductors with stable structures. Valley polarizations are present in the band structures of RuClF/AgBiP2S6 heterostructures with spin-orbit coupling (SOC), the valley splitting energies of which are 279 meV and 263 meV, respectively. The MAEs of RuClF/AgBiP2S6 heterostructures indicate perpendicular magnetic anisotropy (PMA), which are primarily attributed to the differences in matrix elements within Ru (dyz, dz2) orbitals. In addition, valley splittings and MAEs of RuClF/AgBiP2S6 heterostructures are modified at different biaxial strains. Specifically, the highest valley splittings are 283 meV and 287 meV at ε = 2%, while they disappear at ε = -6%. The PMA of RuClF/AgBiP2S6-P↑ is gradually decreased at biaxial strains of -6% to 2%, and MAE is transformed into in-plane magnetic anisotropy (IMA) at ε = 4%. RuClF/AgBiP2S6-P↓ maintains PMA at different strains. The study of non-volatile electrical control of valley splitting phenomena in multiferroic RuClF/AgBiP2S6 heterostructures is crucial in the field of valleytronic devices, which has important theoretical significance.
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Affiliation(s)
- Ziyu Liu
- Tianjin Key Laboratory of Film Electronic & Communicate Devices, School of Integrated Circuit Science and Engineering, Tianjin University of Technology, Tianjin 300384, China.
| | - Baozeng Zhou
- Tianjin Key Laboratory of Film Electronic & Communicate Devices, School of Integrated Circuit Science and Engineering, Tianjin University of Technology, Tianjin 300384, China.
| | - Xiaocha Wang
- Tianjin Key Laboratory of Film Electronic & Communicate Devices, School of Integrated Circuit Science and Engineering, Tianjin University of Technology, Tianjin 300384, China.
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3
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Wang Z, Han X, Liang Y. Large valley splitting and vacancy-induced valley polarization in two-dimensional WSeNH. Phys Chem Chem Phys 2024; 26:17148-17154. [PMID: 38847342 DOI: 10.1039/d4cp01533a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Abstract
The investigation and manipulation of valley pseudospin in promising two-dimensional (2D) semiconductors are essential for accelerating the development of valleytronics. Based on first-principles, we herein report that the WSeNH monolayer is a potential 2D valleytronic material. It is found that stable 2D WSeNH exhibits a semiconducting character with broken inversion symmetry, forming a pair of energy-degenerate but inequivalent valleys at the K and K' points. Arising from the strong spin-orbit coupling strength governed by the W-dxy/dx2-y2 orbitals, it exhibits a large valley splitting of 425 meV at the top of the valence band, which makes it highly plausible for generating the attractive valley Hall effect. Moreover, both valley splitting and optical transition energy can be efficiently modulated by external strain. Furthermore, we find that a considerable valley polarization of 23 meV can be readily realized in 2D WSeNH by introducing hydrogen vacancies. These findings not only broaden the family of 2D valleytronic materials but also provide alternative avenues for valley manipulation.
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Affiliation(s)
- Ziqi Wang
- College of Physics and Optoelectronic Engineering, Faculty of Information Science and Engineering, Ocean University of China, Qingdao 266100, People's Republic of China.
| | - Xuening Han
- College of Physics and Optoelectronic Engineering, Faculty of Information Science and Engineering, Ocean University of China, Qingdao 266100, People's Republic of China.
| | - Yan Liang
- College of Physics and Optoelectronic Engineering, Faculty of Information Science and Engineering, Ocean University of China, Qingdao 266100, People's Republic of China.
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4
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Qiu X, Liu B, Ge L, Cao L, Han K, Yang H. High Curie temperature ferromagnetic monolayer T-CrSH and valley physics of T-CrSH/WS 2 heterostructure. Phys Chem Chem Phys 2024; 26:5589-5596. [PMID: 38284319 DOI: 10.1039/d3cp05543d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2024]
Abstract
Two-dimensional magnetic materials are attracting widespread attention not only for their excellent applications in spintronic devices but also for their potential to regulate valley splitting, which is crucial for valleytronics. Herein, we design a monolayer Janus ferromagnetic semiconductor T-CrSH by using first-principles calculations. We reveal that monolayer T-CrSH has a magnetic moment of 3μB per unit cell, which is primarily contributed by the 3d orbitals of the Cr atom. Monte Carlo simulations suggest that the Curie temperature of T-CrSH is 193 K, and it can rise to 402 K when a 5% tensile strain is applied. Furthermore, the valley degeneracy of WS2 can be lifted when monolayer T-CrSH is used as a substrate. The obtained valley splitting in the conduction band is 13.7 meV and that in the valence band is 157.5 meV. In addition, the large valley polarization of 12.8 meV in the conduction band makes it easy to achieve an electron-doped valley Hall current and spin Hall current when performing in an in-plane electric field.
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Affiliation(s)
- Xiaole Qiu
- School of Physics and Electronic Information, Weifang University, Weifang 261061, China.
| | - Bing Liu
- School of Physics and Electronic Information, Weifang University, Weifang 261061, China.
| | - Lin Ge
- School of Physics and Electronic Information, Weifang University, Weifang 261061, China.
| | - Lianzhen Cao
- School of Physics and Electronic Information, Weifang University, Weifang 261061, China.
| | - Kai Han
- School of Physics and Electronic Information, Weifang University, Weifang 261061, China.
| | - Hongchao Yang
- School of Physics and Electronic Information, Weifang University, Weifang 261061, China.
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5
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Ma X, Fan Y, Li W, Li Y, Liu X, Zhao X, Zhao M. Valley manipulation by sliding-induced tuning of the magnetic proximity effect in heterostructures. NANOSCALE 2023; 15:18678-18686. [PMID: 37933460 DOI: 10.1039/d3nr03086e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
Spontaneous valley polarization, resulting from the magnetic proximity effect, holds tremendous potential for information processing and storage. This effect is highly sensitive to the interfacial electronic properties, encompassing both charge transitions and spin configurations. In this study, we propose the manipulation of valley splitting by leveraging the tunable magnetic proximity effect through sliding an inversion-symmetric antiferromagnetic (AFM-I) monolayer within a TMD/AFM-I/TMD heterostructure. The presence of the antiferromagnetic monolayer enhances the robustness of the magnetic order during interlayer sliding. Notably, we demonstrate that the polarized stacking of the heterostructure enables the generation of intrinsic out-of-plane and in-plane electric polarization. Intriguingly, interlayer sliding not only reverses the out-of-plane and in-plane electric polarization but also alters the layer-resolved valley splitting, thereby contributing to the emergence of the anomalous valley Hall effect and the layer Hall effect. In addition, the manipulation of valleys remains consistent with both the valley optical selection rules and the intra/interlayer emission energy, which are contingent upon the interlayer sliding. The findings of this work hold promise for potential applications in the field of valleytronics.
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Affiliation(s)
- Xikui Ma
- Center for Optics Research and Engineering of Shandong University, Shandong University, Qingdao, 266237, China.
| | - Yingcai Fan
- School of Physics, Shandong University, Jinan, Shandong, 250100, China.
| | - Weifeng Li
- School of Physics, Shandong University, Jinan, Shandong, 250100, China.
| | - Yangyang Li
- School of Physics, Shandong University, Jinan, Shandong, 250100, China.
| | - Xiangdong Liu
- School of Physics, Shandong University, Jinan, Shandong, 250100, China.
| | - Xian Zhao
- Center for Optics Research and Engineering of Shandong University, Shandong University, Qingdao, 266237, China.
| | - Mingwen Zhao
- School of Physics, Shandong University, Jinan, Shandong, 250100, China.
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6
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Sayers C, Genco A, Trovatello C, Conte SD, Khaustov VO, Cervantes-Villanueva J, Sangalli D, Molina-Sanchez A, Coletti C, Gadermaier C, Cerullo G. Strong Coupling of Coherent Phonons to Excitons in Semiconducting Monolayer MoTe 2. NANO LETTERS 2023; 23:9235-9242. [PMID: 37751559 PMCID: PMC10603802 DOI: 10.1021/acs.nanolett.3c01936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 09/19/2023] [Indexed: 09/28/2023]
Abstract
The coupling of the electron system to lattice vibrations and their time-dependent control and detection provide unique insight into the nonequilibrium physics of semiconductors. Here, we investigate the ultrafast transient response of semiconducting monolayer 2H-MoTe2 encapsulated with hBN using broadband optical pump-probe microscopy. The sub-40 fs pump pulse triggers extremely intense and long-lived coherent oscillations in the spectral region of the A' and B' exciton resonances, up to ∼20% of the maximum transient signal, due to the displacive excitation of the out-of-plane A1g phonon. Ab initio calculations reveal a dramatic rearrangement of the optical absorption of monolayer MoTe2 induced by an out-of-plane stretching and compression of the crystal lattice, consistent with an A1g -type oscillation. Our results highlight the extreme sensitivity of the optical properties of monolayer TMDs to small structural modifications and their manipulation with light.
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Affiliation(s)
| | - Armando Genco
- Dipartimento
di Fisica, Politecnico di Milano, 20133 Milano, Italy
| | - Chiara Trovatello
- Dipartimento
di Fisica, Politecnico di Milano, 20133 Milano, Italy
- Department
of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | | | - Vladislav O. Khaustov
- Center
for Nanotechnology Innovation @ NEST, Istituto
Italiano di Tecnologia, 56127 Pisa, Italy
- Scuola
Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy
| | - Jorge Cervantes-Villanueva
- Institute
of Materials Science (ICMUV), University
of Valencia, Catedrático Beltrán 2, E-46980 Valencia, Spain
| | - Davide Sangalli
- Division
of Ultrafast Processes in Materials (FLASHit), Istituto di Struttura della Materia-CNR (ISM-CNR), Area della Ricerca di Roma 1, 00016 Monterotondo, Scalo, Italy
| | - Alejandro Molina-Sanchez
- Institute
of Materials Science (ICMUV), University
of Valencia, Catedrático Beltrán 2, E-46980 Valencia, Spain
| | - Camilla Coletti
- Center
for Nanotechnology Innovation @ NEST, Istituto
Italiano di Tecnologia, 56127 Pisa, Italy
- Graphene
Labs, Istituto Italiano di Tecnologia, 16163 Genova, Italy
| | | | - Giulio Cerullo
- Dipartimento
di Fisica, Politecnico di Milano, 20133 Milano, Italy
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7
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Yu S, Dai Y, Huang B, Wei W. Charge-Transfer-Driven Phase Transition of Two-Dimensional MoTe 2 in Donor-Acceptor Heterostructures. J Phys Chem Lett 2023; 14:7946-7952. [PMID: 37646563 DOI: 10.1021/acs.jpclett.3c02082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
In this work, based on first-principles calculations, we propose that electrene can be considered as an electron-donating substrate to drive the phase transition of MoTe2 from the H to T' phase, which is a topic of long-standing interest and importance. In particular, new electrenes Ca2XN2 (X = Zr, Hf) are predicted with the existence of a nearly free two-dimensional (2D) electron gas and ultralow work functions. In MoTe2/Ca2XN2 donor-acceptor heterostructures, we find significantly large charge transfer (∼0.4e per MoTe2 unit cell) from Ca2XN2 to MoTe2, which stabilizes the T' phase and decreases the phase transition barrier (from ∼0.9 to ∼0.5 eV per unit cell). In addition, the phase transition of MoTe2 on Ca2XN2 remains effective as the interlayer distance varies. It therefore can be confirmed conclusively that our results open a new avenue for phase transition study and provide new insights for the large-scale synthesis of metastable high-quality T'-phase MoTe2.
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Affiliation(s)
- Shiqiang Yu
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Ying Dai
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Baibiao Huang
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Wei Wei
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
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8
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Gogoi L, Gao W, Ajayan PM, Deb P. Quantum magnetic phenomena in engineered heterointerface of low-dimensional van der Waals and non-van der Waals materials. Phys Chem Chem Phys 2023; 25:1430-1456. [PMID: 36601788 DOI: 10.1039/d2cp05228h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Investigating magnetic phenomena at the microscopic level has emerged as an indispensable research domain in the field of low-dimensional magnetic materials. Understanding quantum phenomena that mediate the magnetic interactions in dimensionally confined materials is crucial from the perspective of designing cheaper, compact, and energy-efficient next-generation spintronic devices. The infrequent occurrence of intrinsic long-range magnetic order in dimensionally confined materials hinders the advancement of this domain. Hence, introducing and controlling the ferromagnetic character in two-dimensional materials is important for further prospective studies. The interface in a heterostructure significantly contributes to modulating its collective magnetic properties. Quantum phenomena occurring at the interface of engineered heterostructures can enhance or suppress magnetization of the system and introduce magnetic character to a native non-magnetic system. Considering most 2D magnetic materials are used as stacks with other materials in nanoscale devices, the methods to control the magnetism in a heterostructure and understanding the corresponding mechanism are crucial for promising spintronic and other functional applications. This review highlights the effect of electric polarization of the adjacent layer, changed structural configuration at the vicinity of the interface, natural strain induced by lattice mismatch, and exchange interaction in the interfacial region in modulating the magnetism of heterostructures of van der Waals and non-van der Waals materials. Further, prospects of interface-engineered magnetism in spin-dependent device applications are also discussed.
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Affiliation(s)
- Liyenda Gogoi
- Advanced Functional Materials Laboratory, Department of Physics, Tezpur University (Central University), Tezpur, 784028, India.
| | - Weibo Gao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Pulickel M Ajayan
- Benjamin M. and Mary Greenwood Anderson Professor of Engineering, Department of Materials Science and NanoEngineering, Rice University, 6100 Main Street, Houston, Texas 77005, USA.
| | - Pritam Deb
- Advanced Functional Materials Laboratory, Department of Physics, Tezpur University (Central University), Tezpur, 784028, India.
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9
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Li C, Luo XJ, Chen L, Liu DE, Zhang FC, Liu X. Controllable majorana vortex states in iron-based superconducting nanowires. Natl Sci Rev 2022; 9:nwac095. [PMID: 36196249 PMCID: PMC9521342 DOI: 10.1093/nsr/nwac095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 04/15/2022] [Accepted: 04/15/2022] [Indexed: 11/14/2022] Open
Abstract
To reveal the non-Abelian braiding statistics of Majorana zero modes (MZMs), it is crucial to design a Majorana platform, in which MZMs can be easily manipulated in a broad topological nontrivial parameter space. This is also an essential step to confirm their existence. In this study, we propose an iron-based superconducting nanowire system with Majorana vortex states to satisfy desirable conditions. This system has a radius-induced topological phase transition, giving a lower bound for the nanowire radius. In the topological phase, the iron-based superconducting nanowires have only one pair of MZMs over a wide range of radii, chemical potential and external magnetic fields. The wave function of MZMs has a sizable distribution at the side edge of the nanowires. This property enables the control of the interaction of MZMs in neighboring vortex nanowires and paves the way for Majorana fusion and braiding.
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Affiliation(s)
- Chuang Li
- School of Physics and Institute for Quantum Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Wuhan National High Magnetic Field Center and Hubei Key Laboratory of Gravitation and Quantum Physics, Wuhan, 430074, China
| | - Xun-Jiang Luo
- School of Physics and Institute for Quantum Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Wuhan National High Magnetic Field Center and Hubei Key Laboratory of Gravitation and Quantum Physics, Wuhan, 430074, China
| | - Li Chen
- School of Physics and Institute for Quantum Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Wuhan National High Magnetic Field Center and Hubei Key Laboratory of Gravitation and Quantum Physics, Wuhan, 430074, China
| | - Dong E Liu
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Fu-Chun Zhang
- Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Xin Liu
- School of Physics and Institute for Quantum Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China
- Wuhan National High Magnetic Field Center and Hubei Key Laboratory of Gravitation and Quantum Physics, Wuhan, 430074, China
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10
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Abdollahi M, Bagheri Tagani M. Janus 2H-VSSe monolayer: two-dimensional valleytronic semiconductor with nonvolatile valley polarization. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:185702. [PMID: 35100572 DOI: 10.1088/1361-648x/ac506f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
Valleytronic as a hot topic in recent years focuses on electrons' valley degree of freedom as a quantum information carrier. Here, by combining two-bandk.pmodel with high-throughput density functional theory (DFT) calculations, the valley states of Janus 2H-VSSe monolayer are studied which have spontaneous polarization. Nonvolatile valley polarization state is mainly arises from intrinsic ferromagnetism contributed by V-3d electronic configuration and not the spontaneous out-of-plane dipole moment of VSSe monolayer. The effective Hamiltonian model and DFT calculations both showed that the valley splitting mainly originates from the smaller spin splitting coming from the spin-orbit coupling effect rather than the spin splitting of magnetic exchange field. By using the effective Dirac Hamiltonian and Kubo formula, we further calculated the longitudinal and transversal conductivities and absorption spectra of VSSe monolayer which exhibits an anomalous valley Hall effect and clear valley-selective circular dichroism. Our calculations indicate that the modification of valley and spin splitting related to Berry curvature by applying an external strain is more noticeable than by the change of the magnetic moment orientation and electric field. We found that carriers accumulation with particular spin and valley label can be manipulated by tuning effective Hamiltonian parameters. The coexistence of robust in-plane magnetic ordering and spontaneous valley polarization of 2H-VSSe monolayer supports the possibility of applications in spintronics, valleytronics and optoelectronics devices.
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Affiliation(s)
- Mahsa Abdollahi
- Department of Physics, University of Guilan, P.O. Box 41335-1914, Rasht, Iran
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11
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Pace S, Martini L, Convertino D, Keum DH, Forti S, Pezzini S, Fabbri F, Mišeikis V, Coletti C. Synthesis of Large-Scale Monolayer 1T'-MoTe 2 and Its Stabilization via Scalable hBN Encapsulation. ACS NANO 2021; 15:4213-4225. [PMID: 33605730 PMCID: PMC8023802 DOI: 10.1021/acsnano.0c05936] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 02/02/2021] [Indexed: 06/02/2023]
Abstract
Out of the different structural phases of molybdenum ditelluride (MoTe2), the distorted octahedral 1T' possesses great interest for fundamental physics and is a promising candidate for the implementation of innovative devices such as topological transistors. Indeed, 1T'-MoTe2 is a semimetal with superconductivity, which has been predicted to be a Weyl semimetal and a quantum spin Hall insulator in bulk and monolayer form, respectively. Large instability of monolayer 1T'-MoTe2 in environmental conditions, however, has made its investigation extremely challenging so far. In this work, we demonstrate homogeneous growth of large single-crystal (up to 500 μm) monolayer 1T'-MoTe2 via chemical vapor deposition (CVD) and its stabilization in air with a scalable encapsulation approach. The encapsulant is obtained by electrochemically delaminating CVD hexagonal boron nitride (hBN) from copper foil, and it is applied on the freshly grown 1T'-MoTe2 via a top-down dry lamination step. The structural and electrical properties of encapsulated 1T'-MoTe2 have been monitored over several months to assess the degree of degradation of the material. We find that when encapsulated with hBN, the lifetime of monolayer 1T'-MoTe2 successfully increases from a few minutes to more than a month. Furthermore, the encapsulated monolayer can be subjected to transfer, device processing, and heating and cooling cycles without degradation of its properties. The potential of this scalable heterostack is confirmed by the observation of signatures of low-temperature phase transition in monolayer 1T'-MoTe2 by both Raman spectroscopy and electrical measurements. The growth and encapsulation methods reported in this work can be employed for further fundamental studies of this enticing material as well as facilitate the technological development of monolayer 1T'-MoTe2.
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Affiliation(s)
- Simona Pace
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Leonardo Martini
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
| | - Domenica Convertino
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Dong Hoon Keum
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Stiven Forti
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
| | - Sergio Pezzini
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Filippo Fabbri
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Vaidotas Mišeikis
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Camilla Coletti
- Center
for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy
- Graphene
Laboratories, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
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12
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Coexistence of valley polarization and Chern insulating states in MoS 2 monolayers with n-p codoping. Sci Rep 2020; 10:9851. [PMID: 32555304 PMCID: PMC7300020 DOI: 10.1038/s41598-020-66912-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 05/26/2020] [Indexed: 11/19/2022] Open
Abstract
The electronic and topological properties of MoS2 monolayers with n-p codoping effect are investigated by using first-principles calculations. Two types of the doped Nb atoms play the roles of the p-type and n-type dopants, respectively. The n-p codoping is found inducing a large valley polarization, associated with the strong magnetization induced by the Nb dopants. Interestingly, the system simultaneously owns a perfect Chern insulating band gap opened exactly at the Fermi level. The nontrivial band gap comes from the lifting of the degeneracy of the dxz and dyz orbitals of Nb2 atoms after the spin-orbit coupling is considered. Our work inspires exciting prospects to tune the novel properties of materials with n-p codoping effects.
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13
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Xu X, Ma Y, Zhang T, Lei C, Huang B, Dai Y. Nonmetal-Atom-Doping-Induced Valley Polarization in Single-Layer Tl 2O. J Phys Chem Lett 2019; 10:4535-4541. [PMID: 31342751 DOI: 10.1021/acs.jpclett.9b01602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Valleytronics that relies on the valley degree of freedom is attracting growing interest because it provides a new platform for information storage. One obstacle in this field is to realize valley polarization in an efficient route to manipulate the valley physics. Here we propose a strategy to induce valley polarization by nonmetal atom doping in single-layer Tl2O. Owing to the intrinsic inversion asymmetry and large spin-orbit coupling, there are a two-fold valley degeneracy and an excellent spin-valley independence in single-layer Tl2O. Upon introducing C/N atoms in single-layer Tl2O, the intriguing valley polarization successfully appears, and the obtained polarization strengths are considerable. In particular, for N-doped case, the top valence band locates around the Fermi level, and there are no impurity states in the band gap, which is desirable for practical applications. It is predicted that these valley polarizations can be effectively engineered under the magnetic field and external strain, suggesting that the control of valley physics in single-layer Tl2O is accessible.
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Affiliation(s)
- Xilong Xu
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Shandanan Street 27 , Jinan 250100 , China
| | - Yandong Ma
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Shandanan Street 27 , Jinan 250100 , China
| | - Ting Zhang
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Shandanan Street 27 , Jinan 250100 , China
| | - Chengan Lei
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Shandanan Street 27 , Jinan 250100 , China
| | - Baibiao Huang
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Shandanan Street 27 , Jinan 250100 , China
| | - Ying Dai
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Shandanan Street 27 , Jinan 250100 , China
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Zhang F, Mi W, Wang X. Tunable valley and spin splitting in 2H-VSe 2/BiFeO 3(111) triferroic heterostructures. NANOSCALE 2019; 11:10329-10338. [PMID: 31107480 DOI: 10.1039/c9nr01171d] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The spin and valley degrees of freedom in monolayer transition metal dichalcogenides have potential applications in spintronics and valleytronics. However, nonvolatile control on the valley and spin degrees of freedom of two-dimensional ferromagnetic materials by multiferroic materials has been rarely reported. Here, the electronic structure of monolayer 2H-VSe2/BiFeO3(111) triferroic heterostructures has been investigated by first-principles calculations. It is found that the V magnetic moment, spin and valley splitting of monolayer VSe2 can be affected by the BiFeO3(111) substrate with ferroelectric polarization and G-type antiferromagnetic order. Particularly, the reversed orientation of ferroelectric polarization and magnetic order of the BiFeO3(111) substrate can modulate the magnitude of spin and valley splitting, and change the spin splitting direction and the spin-dependent valley state in the valence band of monolayer VSe2. The coupling among ferroelectrics, magnetism and ferrovalley is realized in 2H-VSe2/BiFeO3(111) triferroic heterostructures. These results provide a new platform for multiferroic regulation in spintronics and valleytronics, which can enrich the diversity for high-performance devices based on two dimensional multiferroic heterostructures.
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Affiliation(s)
- Fang Zhang
- Tianjin Key Laboratory of Low-Dimensional Materials Physics and Preparation Technology, School of Science, Tianjin University, Tianjin 300354, China.
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15
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Cortés N, Ávalos-Ovando O, Rosales L, Orellana PA, Ulloa SE. Tunable Spin-Polarized Edge Currents in Proximitized Transition Metal Dichalcogenides. PHYSICAL REVIEW LETTERS 2019; 122:086401. [PMID: 30932605 DOI: 10.1103/physrevlett.122.086401] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 12/05/2018] [Indexed: 06/09/2023]
Abstract
We explore proximity-induced ferromagnetism on transition metal dichalcogenides (TMDs), focusing on molybdenum ditelluride ribbons with zigzag edges, deposited on ferromagnetic europium oxide (EuO). A tight-binding model incorporates exchange and Rashba fields induced by proximity to EuO or similar substrates. For in-gap Fermi levels, electronic modes in the nanoribbon are localized along the edges, acting as one-dimensional (1D) conducting channels with tunable spin-polarized currents. TMDs on magnetic substrates can become very useful in spintronics, providing versatile platforms to study the proximity effects and electronic interactions in complex 1D systems.
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Affiliation(s)
- Natalia Cortés
- Departamento de Física, Universidad Técnica Federico Santa María, Casilla 110V, Valparaíso, Chile
- Department of Physics and Astronomy, and Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701-2979, USA
| | - O Ávalos-Ovando
- Department of Physics and Astronomy, and Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701-2979, USA
| | - L Rosales
- Departamento de Física, Universidad Técnica Federico Santa María, Casilla 110V, Valparaíso, Chile
| | - P A Orellana
- Departamento de Física, Universidad Técnica Federico Santa María, Casilla 110V, Valparaíso, Chile
| | - S E Ulloa
- Department of Physics and Astronomy, and Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701-2979, USA
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Peng R, Ma Y, Zhang S, Huang B, Dai Y. Valley Polarization in Janus Single-Layer MoSSe via Magnetic Doping. J Phys Chem Lett 2018; 9:3612-3617. [PMID: 29909617 DOI: 10.1021/acs.jpclett.8b01625] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Two-dimensional valleytronic systems can provide information storage and processing advantages that complement or surpass those of conventional charge- and spin-based semiconductor technologies. The major challenge currently is to realize valley polarization for manipulating the valley degree of freedom. Here, we propose that valley polarization can be readily achieved in Janus single-layer MoSSe through magnetic doping, which is highly feasible in experiment. Due to inversion symmetry breaking combined with strong spin-orbit coupling (SOC), the pure single-layer MoSSe harbors an intriguing multivalleyed band structure and strong coupled spin and valley physics. After doping Cr/V, the long-sought valley polarization is successfully achieved with a remarkable energy difference of ∼0.06 eV upon switching on SOC. Furthermore, the valley polarization in Cr/V-doped single-layer MoSSe is tunable via strain engineering. Our work thus provides a promising platform for experimental studies and applications of the valleytronics.
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Affiliation(s)
- Rui Peng
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Shandanan Street 27 , Jinan 250100 , China
| | - Yandong Ma
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Shandanan Street 27 , Jinan 250100 , China
| | - Shuai Zhang
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Shandanan Street 27 , Jinan 250100 , China
| | - Baibiao Huang
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Shandanan Street 27 , Jinan 250100 , China
| | - Ying Dai
- School of Physics, State Key Laboratory of Crystal Materials , Shandong University , Shandanan Street 27 , Jinan 250100 , China
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