Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session V15: 2D Materials (Semiconductors) -- Emerging Materials IIFocus
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Sponsoring Units: DMP DCOMP Chair: Brian Kiraly, Radboud University Room: BCEC 154 |
Thursday, March 7, 2019 2:30PM - 2:42PM |
V15.00001: WITHDRAWN ABSTRACT
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Thursday, March 7, 2019 2:42PM - 2:54PM |
V15.00002: First principles studies of 2D transition metal dichalcogenides on 3D magnetic oxides Elizabeth Peterson, Jeffrey B Neaton Monolayer transition metal dichalcogenides are desirable for new high-speed, low-power and miniaturized valley optoelectronics. One way to create valley polarization is via magnetic proximity coupling, facilitated by interfacing single-layer TMDs and magnetic substrates; this approach has recently been shown to generate significantly larger valley splitting than applied magnetic fields. However, the reported valley splitting is still relatively small and the details of the interface between TMDs and magnetic substrates are poorly understood. Using first principles and model calculations, we explore the structure of the TMD-oxide interface, and predict the magnitude of the valley splitting generated by proximity to magnetic substrates. We examine the most critical attributes of this interface and develop general design principles that connect the structure of TMD-oxide interfaces to functionality relevant for valleytronics. |
Thursday, March 7, 2019 2:54PM - 3:06PM |
V15.00003: Tunable band alignment in 2D ferroelectric In2Se3 based van der Waals heterostructures Zhe Wang, Wenguang Zhu Van der Waals heterostructures with the advantages of atomically sharp interfaces, digitally controlled layered components, and no lattice parameter constraint, have been attracted substantial research interests in recent years due to their great potentials in electronic and optoelectronic applications and such properties critically depend on the band alignment between the constituent layers. Here we, based on first-principles calculations, demonstrate that by taking advantage of a recently discovered 2D ferroelectric material In2Se3 its van der Waals heterostructures with other known 2D materials have the ability to tune their band alignment between different types of semiconductor junctions or the Schottky barrier height by switching the orientation of the electric polarization of the ferroelectric In2Se3 layer with an external electric field. This work provides a generic guideline for the application of the 2D ferroelectric In2Se3 in tuning the electronic properties of van der Waals heterostructures. |
Thursday, March 7, 2019 3:06PM - 3:18PM |
V15.00004: The two-dimensional ferroelectric material GaTeCl monolayer Shi-Hao Zhang, Bang-Gui Liu Searching for new ferroelectric atomic-thick materials is an important issue in the condensed matter physics. Through first-principles investigation we proposed a new two-dimensional ferroelectric material GaTeCl monolayer which can be exfoliated from pre-existing GaTeCl bulk. The calculated in-plane ferroelectric polarization reaches 578 pC/m. The energy barriers per formula unit of the ferroelastic 90-degrees rotational and ferroelectric reversal transitions are 476 meV and 754 meV respectively. A tensile stress of 4.7 N/m perpendicular to the polarization can drive the polarization to rotate by 90 degrees. The second harmonic generation susceptibility calculations reveal that the GaTeCl monolayer has giant optical second harmonic generation with the intensity being strongly anisotropic. These ensure the great potential of GaTeCl monolayer in high-performance multi-functional applications. |
Thursday, March 7, 2019 3:18PM - 3:30PM |
V15.00005: Injection current in single-layer group IV-monochalcogenides Suman Panday, Benjamin M. Fregoso Single-layer group-IV monochalcogenides GeS, GeSe, SnS, SnSe are two-dimensional ferroelectrics predicted to exhibit giant second harmonic generation and photovoltaic shift current. Using density functional theory methods, we show that these materials also exhibit giant injection current (circular photogalvanic effect). The magnitude can reach values up to 1011 A/V2S in the visible spectrum which is two orders of magnitude larger than that of prototypical nonlinear semiconductor CdS. We discuss the correlations between injection current, density of states and electric polarization using analytical and numerical methods. The injection current varies nonmonotonically with polarization reaching a maximum at an optimal polarization but is not correlated with the density of states. Our results establish GeS, GeSe, SnS, SnSe as versatile nonlinear materials suitable for optoelectronic applications. |
Thursday, March 7, 2019 3:30PM - 3:42PM |
V15.00006: ABSTRACT WITHDRAWN
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Thursday, March 7, 2019 3:42PM - 3:54PM |
V15.00007: Tuning band structures and electronic properties of few-layer InSe by uniaxial strain Chaoyu Song, Feng-Ren Fan, Ningning Xuan, Shenyang Huang, Guowei Zhang, Chong Wang, Zhengzong Sun, Hua Wu, Hugen Yan Atomically thin InSe joins the family of 2-dimensional materials recently with the advantage of high carrier mobility and layer-dependent bandgap. In this work, we engineer the band structures of few-layer InSe by uniaxial tensile strain. Prominent redshifts (90-100 meV per 1% strain) of photoluminescence peaks were observed in 4- to 8-layer samples. Density functional calculations well reproduce the observed strain effect and reveal that the shift rate decreases with increasing layer number for few-layer InSe, which can be understood based on the strain-induced change of the inter-layer interactions. In addition, resonant Raman spectroscopy was employed to study the vibrational properties of few-layer InSe. Sizable strain-induced redshifts of first order phonon modes and resonance effect were observed. |
Thursday, March 7, 2019 3:54PM - 4:06PM |
V15.00008: Ab initio Carrier Mobility of Two-Dimensional Indium Selenide Wenbin LI, Samuel Ponce, Feliciano Giustino Owing to its exceptionally high electron mobility, indium selenide (InSe) is emerging as one of the most promising layered semiconductors for two-dimensional electronics and optoelectronics. However, the intrinsic carrier mobility of InSe in the monolayer limit and the corresponding carrier scattering mechanisms remain unknown. By performing ab initio calculations of the intrinsic carrier mobility of InSe in the Boltzmann transport formalism, we find that the electron carriers in InSe are predominantly scattered by the coupling to longitudinal-optical phonons, namely the Fröhlich interaction. We also find that the carrier mobility of InSe exhibits strong layer dependence. At 300 K, the electron mobilities of InSe are found to be 120, 220, and 1060 cm2V-1s-1 for monolayer, bilayer and bulk, respectively, in good agreement with transport measurements. |
Thursday, March 7, 2019 4:06PM - 4:18PM |
V15.00009: First-principles studies on electronic band structure of PdSe2 with GW approximation Han-gyu Kim, Hyoung Joon Choi We studied the electronic band structure of PdSe2 using the density functional theory (DFT) and the GW method. It is known that PdSe2, a material with stacks of pentagonal layer structure, has a semiconducting band structure experimentally. However, DFT calculations show that bulk PdSe2 has a semi-metallic band structure because of DFT underestimation of the band gap of the material. To obtain the band gap of PdSe2 correctly, we calculated the quasiparticle band structure of bulk PdSe2 using the one-shot GW method and obtained a band gap which is consistent with experimental results. Then we calculated the electronic structure of two-dimensional PdSe2 to investigate the layer-number dependence on the energy gap. We discuss band-to-band transition energies and other physical properties obtained from band structures of PdSe2. |
Thursday, March 7, 2019 4:18PM - 4:54PM |
V15.00010: Scalably-nanomanufactured atomically-thin piezoelectric semiconductor for ubiquitous electronics and smart sensors Invited Speaker: Wenzhuo Wu The reliable production of atomically-thin crystals is essential for exploring new science and implementing novel technologies in the 2D limit. In this talk, I will discuss our recent discovery of a new 2-D piezoelectric semiconductor, tellurene, synthesized by a substrate-free solution process. The tellurene crystals exhibit process-tunable thicknesses from a monolayer to tens of nanometers, and lateral sizes ~ 100 mm. Our prototypical tellurene transistor device, which is air-stable, shows an excellent all-around figure of merits compared to existing 2D materials. We further carry out the first experimental exploration of piezotronic effect in tellurene and systematically investigate the piezotronic transport properties. The fundamental understanding of piezotronic coupling in tellurene is expected to provide insights for the development of 2-D material piezotronics and electronics, leading to the realization of “smarter” electronics for a multitude of emerging technologies, e.g., wearable electronics, soft robotics, medical prosthetics, and human-machine interface. |
Thursday, March 7, 2019 4:54PM - 5:06PM |
V15.00011: ABSTRACT WITHDRAWN
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Thursday, March 7, 2019 5:06PM - 5:18PM |
V15.00012: Study of dipolar excitons in TiS3 double layer Roman Kezerashvili The most studied layered semiconductors to date are the transition metal dichalcogenides and nowadays there is a flurry of effort to study the transition metal trichalcogenides (TMTC) with MX3 composition (M is a metal X is a chalcogen) that have highly anisotropic crystal structure. We present the results of study of the formation of dipolar excitons in a TMTC double layer in the framework of a Wannier-Mott model for the indirect excitons that takes into account the anisotropic effective masses. The energy spectrum and wave functions for a single dipolar exciton are obtained and binding energies are calculated within the harmonic oscillator approximation for the Rutova-Keldysh and Coulomb potentials. In the framework of the Bogoliubov approximation spectrum of collective excitations for the dilute weakly interacting Bose gas of dipolar excitons si studied and the mean field critical temperature for the superfluidity is obtained. It is demonstrated that as a result of the strong in-plane anisotropy, superfluidity is vastly differ in different crystalline directions. The calculations are performed for a direct band gap semiconductor TiS3 that is a prototypical representative of TMTC materials. |
Thursday, March 7, 2019 5:18PM - 5:30PM |
V15.00013: Van der Waals charge-transfer interfaces Yuta Kashiwabara, Masaki Nakano, Yuji Nakagawa, Yue Wang, Hideki Matsuoka, Yoshihiro Iwasa The creation of functional interfaces between different materials has often led to a discovery of a unique electronic property and functionality that is missing in the constituent materials, providing an invaluable material platform in modern science and technology. 2D materials are suitable compounds for construction of such an interface due to existence of the van der Waals gap that enables creation of an atomically-abrupt interface, and in fact various types of heterostructures named ‘van der Waals heterostructures’ have been more and more developed for the last few years. However, those researches have mainly focused on electrical transport across the interface, while lateral transport properties along the interface have been less studied so far. In this presentation, we will demonstrate emergence of electrical conduction at the interface between insulating 2D materials fabricated by molecular-beam epitaxy with our growth recipe [1]. [1] M. Nakano, et. al., Nano Lett. 17, 5595 (2017). |
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