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 B34: Optical Spectroscopic Measurements of 2D Materials IIIndustrial
|
Hide Abstracts |
Sponsoring Units: FIAP Chair: Wei-Sheng Lee, SLAC - Natl Accelerator Lab Room: Room 226/227 |
Monday, March 6, 2023 11:30AM - 11:42AM |
B34.00001: Quasi-1D Exciton Channels in Strain-Engineered 2D Materials Florian Dirnberger, Jonas D Ziegler, Vinod M Menon, Alexey Chernikov Strain engineering is a powerful tool in the design of high temperature excitonic devices. Two-dimensional transition metal dichalcogenides (2D TMDCs) harbor enormous potential in this regard because they unify excellent elasticity with robust and highly mobile exciton quasiparticles. However, steering these neutral quasiparticles along predesigned pathways has proven to be exceptionally difficult. |
Monday, March 6, 2023 11:42AM - 11:54AM |
B34.00002: Localized electric-field induced defects in hexagonal boron nitride for site-controlled quantum emitters Zhen You Lin Controlling the sites of artificial defects in two-dimensional materials is a critical challenge in color center applications such as quantum emission, quantum communication, and quantum cryptography. Recently, the color center of hexagonal boron nitride (h-BN) has a wide range and brightness of emission light at room temperature, chemical and thermal robustness leading to more and more attention recently. We here investigate color centers in h-BN created by applying a tip-induced electric field, and the tip position controls the sites of the color centers. Due to prevent the emission of various organic residues from typical transferring processes coupling into color center emission, here we directly create defects on the h-BN grown by using plasma-assisted molecular beam epitaxy (PA-MBE) on SiC substrate with single crystalline quality and large area up to wafer scale. A variety of intensity, energy, and position control in h-BN defects are observed in scanning microscopies with morphology and luminescence visibilities. And the quantum phenomenon is characterized by pronounced single-photon antibunching in a zero-delay time. Because of the controllability of the defect position, the emission properties are also highly controllable in our h-BN systems and, thus, can potentially be tuned for future quantum optical applications. |
Monday, March 6, 2023 11:54AM - 12:06PM |
B34.00003: Nematicity in SnS single crystals probed by ultrafast spectroscopy Chih-Wei Luo, Nguyen Nhat Quyen, Tz-Ju Hong, Chin En Hsu, Wen-Yen Tzeng, Chien-Ming Tu, Chia-Nung Kuo, Hung-Chung Hsueh, Chin-San Lue SnS is one of the promising materials for the applications of optoelectronics and photovoltaics. This study determines the nematic dynamics of photoexcited electrons and phonons in SnS single crystals using polarization-dependent ultrafast spectroscopy at various temperatures. Besides the fast relaxation of photoexcited electrons, a damped oscillation component with a frequency of 36~41 GHz is also present in transient reflectivity change (ΔR/R) spectra, which is generated by the thermoelastic effect. The results of this study show that electrons and coherent acoustic phonons demonstrate significant anisotropy on the ac-plane in the transition region from 330 K to 430 K, possibly because of strong electron-phonon coupling (e.g., 1.16 along a-axis at 300 K). However, this in-plane anisotropy weakens dramatically in the low-temperature (< 330 K) and high-temperature (> 430 K) phases. These play an important role in anisotropic heat dissipation and charge carrier mobility in polarization-sensitive optical and optoelectronic devices. |
Monday, March 6, 2023 12:06PM - 12:18PM |
B34.00004: Ultrafast nano-imaging of electronic coherence of monolayer WSe2 Wenjin Luo, Benjamin G Whetten, Vasily Kravtsov, Ashutosh K Singh, Yibo Yang, Di Huang, Xinbin Cheng, Tao Jiang, Alexey Belyanin, Markus B Raschke Transition metal dichalcogenides (TMDs) have demonstrated a wide range of novel photonic, optoelectronic, and correlated electron phenomena for more than a decade. However, the effect of spatial heterogeneities on their exciton coherence dynamics with possibly long dephasing times is still poorly understood. Here, we image the coherent electron dynamics in monolayer WSe2 using correlative adiabatic plasmonic nanofocused four-wave mixing (FWM) measurements. We resolve nanoscale heterogeneity on time scales ranging from less than 10 to greater than 45 fs at room temperature. We find a counterintuitive spatial anti-correlation between FWM and dephasing time which we interpret as a result of the impact of heterogeneous disorder on the spatial coherence of the nonlinear FWM polarization. These findings highlight the fundamental challenges caused by heterogeneities in TMDs and the resulting limits on photophysical properties. |
Monday, March 6, 2023 12:18PM - 12:30PM |
B34.00005: Excitonic interaction-driven transport and dynamics of dark states in 2D semiconductors Saroj B Chand, John M Woods, Jiamin Quan, Enrique Majia Excitonic quantum fluid in transition metal dichalcogenides (TMDs) has recently emerged as a promising research focus for studying many-body physics and applications for efficient and tunable excitonic devices. The multivalley band structure and large spin-orbit coupling in TMDs result in an abundance of optically bright and dark excitonic states with different spin/valley configurations. In particular, the dark excitons have a permanent out-of-plane dipole, large binding energy, and a long lifetime. Therefore, they are promising candidates for long-range transport driven by exciton-exciton interaction. Here, we show that both direct and exchange Coulomb excitonic interactions are repulsive and they enhance the dark exciton transport. By employing a high-resolution spatially resolved PL setup in an encapsulated monolayer of WS2, we demonstrate that dark exciton can diffuse up to several micrometers. Furthermore, we conduct experiments in the engineered exciton landscape and show that the repulsive interaction can provide additional energy to dark exciton to propagate in an uphill energy landscape. This repulsion-driven long-range transport of dark states provides a route for excitonic devices that could be used for both classical and quantum information processing. |
Monday, March 6, 2023 12:30PM - 12:42PM |
B34.00006: Thickness-Dependent Relaxation of Near-IR Excitons in 2D CrCl3 Hyesun Kim, Sunmin Ryu Two-dimensional (2D) chromium(III) chloride (CrCl3) is promising for optoelectronic devices and magnetic sensors because of its intrinsic magnetism in the monolayer limit and strong visible absorption of its bulk form.[1] In this work, we studied the excitonic behaviors of few-layer to bulk CrCl3 using absorption, photoluminescence (PL) spectroscopy and time-correlated single-photon counting (TCSPC). There was no significant spectral change with the number of layers in absorption and PL signals, which may originate from a localized nature of the near-IR excitons. However, the PL lifetime showed a drastic reduction from 4.5 μs to 1 ns with decreasing thickness from bulk to 1.4 nm. Control experiments with ozone-generated defects and encapsulation with hexagonal BN sandwich support that structural defects are responsible for the accelerated relaxation in 2D forms. In addition, the transition from indirect to direct bandgap may play some role in the observed change. Temperature-dependent spectral and kinetic changes will also be discussed regarding the nature of the excitons. |
Monday, March 6, 2023 12:42PM - 12:54PM |
B34.00007: All-optical control of ultrathin trionic waveguide Hyeongwoo Lee, Yeonjeong Koo, Shailabh Kumar, Yunjo Jeong, Soo Ho Choi, Huitae Joo, Mingu Kang, Radwanul H Siddique, Ki Kang Kim, Sangmin An, Hyuck Choo, Kyoung-Duck Park The generation of high-purity localized trions, dynamic exciton-trion interconversion, and their spatial modulation in 2D semiconductors are building blocks for realizing trion-based optoelectronic devices. Here, we present an all-optical control of the trionic conversion process and its spatial distributions in a MoS2 monolayer, demonstrating an ultrathin trionic waveguide. We induce the nanoscale strain gradient in a 2D crystal transferred on the metal-insulator-metal (MIM) waveguide and exploit the propagating surface plasmon polariton (SPP) to localize the hot electrons. These significantly increased electrons and efficiently funneled excitons in the MIM waveguide facilitate complete exciton-to-trion conversion even under ambient conditions. Additionally, we modulate the SPP mode using adaptive wavefront shaping, enabling the all-optical control of the exciton-to-trion conversion rate and the trion distribution in a reversible manner. Our work paves the way for the development of hybrid plasmo-excitonic integrated circuits that combine efficient plasmonic transport with highly radiative excitonic emission. |
Monday, March 6, 2023 12:54PM - 1:06PM |
B34.00008: Tunable interlayer excitons and switchable interlayer trions via dynamic near-field cavity Yeonjeong Koo, Hyeongwoo Lee, Tatiana Ivanova, Ali Kefayati, Vasili Perebeinos, Ekaterina Khestanova, Roman Savelev, Mihail Petrov, Vasily Kravtsov, Kyoung-Duck Park Emerging photo-induced excitonic processes in transition metal dichalcogenide (TMD) heterobilayers, e.g., interplay of intra- and inter-layer excitons and conversion of excitons to trions, allow new opportunities for ultrathin hybrid photonic devices. However, with the associated large degree of spatial heterogeneity, understanding and controlling their complex competing interactions in TMD heterobilayers at the nanoscale remains a challenge. Here, we present an all-round dynamic control of interlayer-excitons and -trions in a WSe2/Mo0.5W0.5Se2 heterobilayer using multifunctional tip-enhanced photoluminescence (TEPL) spectroscopy with <20 nm spatial resolution. Specifically, we demonstrate the bandgap tunable interlayer excitons and the dynamic interconversion between interlayer-trions and -excitons, through the combinational tip-induced engineering of GPa-scale pressure and plasmonic hot electron injection, with simultaneous spectroscopic TEPL measurements. Furthermore, through optical wavefront shaping, we selectively modulate TEPL responses of intra- and inter-layer excitons in ∼25 nm2 area demonstrating the enabling concept of an ultrathin 2-bit nano-excitonic transistor. We suggest a simple theoretical model describing the underlying adaptive TEPL modulation mechanism. This unique nano-opto-electro-mechanical control approach provides new strategies for developing versatile nano-excitonic/trionic devices using TMD heterobilayers. |
Monday, March 6, 2023 1:06PM - 1:18PM |
B34.00009: Dynamically tunable moiré exciton in monolayer WSe2 on twisted bilayer graphene Minhao He, Jiaqi Cai, Huiyuan Zheng, Eric Seewald, Kenji Watanabe, Takashi Taniguchi, Jiaqiang Yan, Matthew A Yankowitz, Abhay N Pasupathy, Wang Yao, Xiaodong Xu Excitons arranged in periodic arrays are highly desired for various quantum optoelectronics application. Moiré quantum materials provide an ideal setting where excitons can be trapped by the deep moiré potential with engineered periodicity. Yet, a system with dynamically tunable moiré potential is to be demonstrated. In this talk, we present realization of a tunable moiré potential in a monolayer WSe2 that are enabled by its adjacent twisted bilayer graphene (tBLG). We observe a set of emergent moiré exciton Rydberg states at finite doping of tBLG, with their energy splitting increasing with tBLG doping. These observation can be understood as a result of enhanced moiré potential with tBLG doping. Our work opens new possibilities in engineering of the moiré potential in a monolayer semiconductor. |
Monday, March 6, 2023 1:18PM - 1:30PM |
B34.00010: Optical detection of electrostatically generated interlayer excitons Andrew Joe, Ruishi Qi, Tiancheng Zheng, Zuocheng Zhang, Jingxu Xie, Emma Regan, Zheyu Lu, Takashi Taniguchi, Kenji Watanabe, Sefaattin Tongay, feng wang Interlayer excitons in transition metal dichalcogenide (TMD) heterostructures have been of great interest because of their potential to form a high temperature exciton condensate. Their large binding energies and long lifetimes allow interlayer excitons to exist within a large phase space of densities and temperatures. In a type-II band aligned MoSe2/hBN/WSe2 heterostructure, we electrostatically create interlayer excitons by independently controlling the charge densities in the electron and hole layers. The electron and hole densities in the exciton regime are calibrated by optical absorption in the uncorrelated regime. From the calibrated densities we observe a non-linear increase of the exciton density as a function of the bias voltage. Our observations can be qualitatively explained by a model consisting of permanent out-of-plane dipoles with a finite binding energy. The ability to create interlayer excitons in the electrostatic equilibrium limit lays the foundation towards systematically studying interlayer exciton transport in the condensate phase. |
Monday, March 6, 2023 1:30PM - 1:42PM |
B34.00011: Highly Excited Rydberg Excitons in Thin-Film Cuprous Oxide Jacob DeLange, Kinjol Barua, Hadiseh Alaeian, Stephan Steinhauer Photons play an important role in quantum technology because they resist environmental perturbation and can be sent over long distances with minimal loss. However, photons do not interact with each other in linear media, making strong photon nonlinearities indispensable for orchestrating many-body phenomena. Rydberg electronic states with high principal quantum numbers provide these nonlinearities via strong interactions facilitated by their extended wavefunctions. Of particular interest are Rydberg excitons in solid-state hosts, which marry the unmatched interaction strengths of Rydberg states with the scalability of solid-state systems. Cuprous oxide (Cu2O) is an especially promising host whose unique band structure and crystal lattice symmetry allow it to support long-lived, highly excited Rydberg excitons. |
Monday, March 6, 2023 1:42PM - 1:54PM |
B34.00012: Infrared photoresponse of graphene-WTe2 van der Waals heterojunctions Farima Farahmand, Jacky Wan, Nathaniel M Gabor Graphene and WTe2 are atomically thin semimetals with low density of states at their charge neutrality points. While graphene hosts Dirac-like excitations with highly symmetric electron and hole bands, WTe2 is a type II Weyl semimetal with compensated electron-hole pockets. Here we use near-infrared scanning photocurrent microscopy to study the photoexcited electron dynamics that govern the electrical and optical conductivities at the van der Waals heterostructure interface. Interlayer photocurrent observed only at the interface between the materials, exhibits gate voltage dependence reminiscent of the photo-thermoelectric effect, previously observed in the hot carrier regime of graphene. Our measurements - which establish the essential photocurrent characteristics of this combined Dirac-Weyl system - also inform the design and development of highly sensitive infrared sensors based on van der Waals heterostructures. |
Monday, March 6, 2023 1:54PM - 2:06PM |
B34.00013: Intralayer Excitons in Graded Alloys of MoxW1-xS2 Monolayers compared to pristine MoS2, and WS2 Mahdi Ghafariasl, Tianyi Zhang, Zachary Ward, Da Zhou, Venkataraman Swaminathan, Humberto Terrones, Mauricio Terrones, Yohannes Abate We employed an additive-assisted synthesis technique to prepare single-crystalline monolayers of alloyed MoxW1-xS2 and investigated their optical properties at the nanoscale. The monolayer has tunable band gaps in a broad range of 1.70–2.05 eV displaying prominent variations in sulfur composition from the center to the edge regions. The existence of excitons, trions, and defect-bound excitons are investigated using power-dependence and temperature-dependent (4 K−300 K) photoluminescence spectroscopy. Detailed analysis of the alloyed monolayer reveals evidence of new types of defect-bound excitons originating at low temperatures compared to pristine MoS2 and pristine WS2 |
Monday, March 6, 2023 2:06PM - 2:18PM |
B34.00014: Selective Surface-Enhanced Raman Scattering-based Sensing on 2D Niobium Carbide (Nb2CTX) MXene Tej B Limbu, Mackenzie Songsart-Power, Joseph Tran, Brady Wilson, Chetan Dhital, Fei Yan MXenes, a new family of 2D metal carbides/nitrides/carbonitrides, have attracted considerable interest in surface-enhanced Raman scattering (SERS), owing to their excellent electronic properties and superhigh hydrophilicity. However, Niobium carbide (Nb2CTX) MXene, a second representative of the MXene family, has not been explored much for SERS applications. Herein, we report a successful exfoliation of high-quality and fewlayered Nb2CTX nanosheets from its MAX phase (Nb2AlC) and studied SERS activities using methylene blue (MB), rhodamine 6G (R6G), and crystal violet (CV) as probe molecules, employing the laser excitation of 532 nm. The results showed that the Raman enhancement of the dye molecules on Nb2CTX-based SERS substrate was dependent on the laser-molecule combination, giving the highest enhancement for CV and lowest for MB at 10-4 M concentration. Moreover, only CV was detected from the mixture of all three dyes at a lower concentration 10-5 M, indicating a possibility of selective SERS sensing on novel 2D materials like Nb2CTX. The results clearly infer that the charge transfer interaction plays a major role in the SERS mechanism. Our findings provide an insight on the development of inexpensive, and selective SERS substrates based on 2D MXenes for molecular detection. |
Monday, March 6, 2023 2:18PM - 2:30PM |
B34.00015: Every-other-layer Dipolar Excitons in a Spin-Valley locked Superlattice Yinong Zhang, Chengxin Xiao, Dmitry Ovchinnikov, Jiayi Zhu, Xi Wang, Takashi Taniguchi, Kenji Watanabe, Jiaqiang Yan, Wang Yao, Xiaodong Xu In 2H stacked pristine multilayer transition metal dichalcogenides, the spin-valley locking effect yields an electronic superlattice structure, where alternating layers correspond to barrier and quantum well respectively, conditioned on the spin-valley indices. We show that the spin-valley locked superlattice hosts a new kind of dipolar excitons with the electron and hole constituents separated in an every-other-layer configuration. Such excitons become optically bright via hybridization with intralayer excitons, displaying multiple anti-crossing patterns in optical reflection spectrum as the dipolar exciton is tuned through the intralayer resonance by electric field. The reflectance spectra also reveal an excited state orbital of the every-other-layer exciton, pointing to a sizable binding energy in the same order of magnitude as the intralayer exciton. As layer thickness increases, the dipolar exciton can form one-dimensional Bose-Hubbard chain displaying a layer number dependent fine-structures in the reflectance spectra. |
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