Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session B15: Electron Dynamics in Quantum Dots and 2D Materials |
Hide Abstracts |
Sponsoring Units: DMP Chair: Zhenfei Liu, Lawrence Berkeley National Laboratory Room: LACC 304C |
Monday, March 5, 2018 11:15AM - 11:27AM |
B15.00001: Nonzero average current in kicked symmetry and asymmetry nanomechanical shuttles Pinquan Qin, Hee Chul Park We studied the average current in kicked nanomechanical shuttles. A kicked ac voltage is applied into the system. This ac voltage consists two parts. One part is normal sine function with frequency ω. The other is pulsed comb like function with frequency ωk. The ac voltage was applied into both left-right symmetry and asymmetry shuttle systems. For the normal shuttle, the left-right symmetry keep the average current zero. However, for the kicked nanomechanical shuttle, even the system keep the left-right symmetry, it have nonzero average current. This nonzero average current exist in both regular and chaos motion region of shuttles. For asymmetry nanomechanical shuttle system, the frequency and strength of pulsed ac voltage show strong effect on the average current. For some special frequency of pulsed ac voltage, the nonzero average current exist in any tongues. For high frequency and strong pulsed ac voltage, the nanomechanical shuttle system are trained robust from systemic parameters, such as the strength of normal sine function voltage. These effects make the kicked pulsed ac voltage highly useful in the realistic application of nanomechanical shuttles. |
Monday, March 5, 2018 11:27AM - 11:39AM |
B15.00002: Transient dynamics through a magnetic tunnel junction Narasimha Raju Chebrolu, Sung Po Chao We present a model study on the time-dependent charge transport through a magnetic |
Monday, March 5, 2018 11:39AM - 11:51AM |
B15.00003: Dynamical Coulomb Blockade in an avalanche diode at room temperature Karl Thibault, Julien Gabelli, Christian Lupien, Bertrand Reulet Dynamical Coulomb Blockade refers to the transport properties of a conductor being affected by its electromagnetic environment. It is usually attributed to the discreteness of the charge carriers, observable at very low temperature and explained in terms of quantum mechanics. It can also be understood in terms of a feedback effect of the noise of the conductor on itself through an external impedance. While quantum noise may be involved in this process, it is not a key ingredient: all that is needed is to have a sample which exhibits voltage-dependent noise. Such classical Dynamical Coulomb Blockade should be observable with many devices even at room temperature. We have measured dc transport and noise of an avalanche diode in series with a resistor. By playing with the value of the external resistor, which controls the strength of the feedback, we demonstrate experimentally the existence of huge Dynamical Coulomb Blockade. We discuss a simple theoretical picture. |
Monday, March 5, 2018 11:51AM - 12:03PM |
B15.00004: Photon-assisted Dynamical Coulomb Blockade in a Tunnel Junction Samuel Houle, Bertrand Reulet, Karl Thibault, Edouard Pinsolle, Christian Lupien We report measurements of photon-assisted transport and noise in a tunnel junction in the regime of dynamical Coulomb blockade. We have measured both dc non-linear transport and low frequency noise in the presence of an ac excitation at frequencies up to 33 GHz. In both experiments we observe replicas at finite voltage of the zero bias features, a phenomenon characteristic of photon emission/absorption. However, the ac voltage necessary to explain our data is notably different for transport and noise, indicating that usual theory of photon-assisted phenomena fails to account for our observations. |
Monday, March 5, 2018 12:03PM - 12:15PM |
B15.00005: Photo-induced Current through Molecular Junction in the Weak Molecule-Lead Coupling Limit Bo Fu, George Schatz, Mark Ratner, Liang-Yan Hsu Photo-induced electron transport through a single molecule is studied in the limit of weak molecule-lead coupling using the Pauli master equation method that propagates the probabilities of the many-body states of the molecular Hamiltonian. Assuming a continuous wave (CW) light source in resonance with the singlet-singlet transition, we show that optical excitation modifies the current by inducing populations of excited electronic states. In contrast with previous studies, the triplet state and singlet-triplet transition are considered in our model, and they are found to play an important role in the photo-induced conduction. The steady current in the sequential transmission regime is calculated for the dependence on gate voltage, external field, asymmetric coupling ratio and light polarization. In different regimes that vary by the energy level of the charged state, we find that the optical excitation may switch on current by pumping up population in the triplet state, or suppress current by reducing the population of the singlet ground state. A near-zero onset voltage of photo-induced conduction is observed when the transport gap is aligned with the energy level of the triplet state. |
Monday, March 5, 2018 12:15PM - 12:27PM |
B15.00006: Orientation Modulated Hot Charge Carrier Transport in Quantum Dot Solids Lesheng Li, Yosuke Kanai Advances in the synthesis of colloidal quantum dots (QDs) have made it possible to engineer the QDs film at the atomistic level, including the control over how QDs are oriented in QD solids. Understanding how the QD orientation impacts charge carrier transport in QD solids is central to the rational design and optimization of QDs devices. Using first-principles quantum dynamics simulations, we investigated the transfer process of excited electrons and holes across silicon QDs with different orientations. We considered how a doubly-bonded oxygen defect at the QD surface impacts the transfer since it is one of the most commonly found and electronically active defects in experiments. Excited electron transfer between the QDs was found to be quite sensitive to the QD orientation. Excited hole, on the other hand, does not show such strong dependence on the orientation. Our results highlight the importance of the atomistic details of colloidal QDs for understanding charge transport properties. |
Monday, March 5, 2018 12:27PM - 12:39PM |
B15.00007: Charge Transfer and Spin Dynamics at Hybrid Organic-2D Layered Crystal Interfaces Tika Kafle, Bhupal Kattel, Samuel Lane, Hui Zhao, Wai Lun Chan Two-dimensional (2D) van der Waals heterostructures have received much attention recently because it provides the feasibility in tailoring material properties on the nanoscale. 2D materials such as transition metal dichalcogenide (TMD) can further be combined with other materials such as organic semiconducting crystals to form interfaces with unique properties. In this work, we study the charge transfer properties at zinc phthalocyanine (ZnPc)-MoS2 and ZnPc-WSe2 interfaces using time-resolved photoemission spectroscopy. At both interfaces, it is found that the optically excited singlet exciton in ZnPc transfers its electron to the TMD layer in ~ 100 fs. However, back electron transfer can also occur in ~ 1-100 ps at the ZnPc-MoS2 interface, which results in the formation of a triplet exciton in the ZnPc layer. This back electron transfer process originates from a combination of the strong spin-orbit coupling in TMD crystals and the large exchange interaction in organic crystals. Even though the back electron transfer would reduce the yield of free charge carrier generation at the heterojunction, the spin–selective back electron transfer could provide new possibilities in manipulating electron spin in hybrid electronic devices. |
Monday, March 5, 2018 12:39PM - 12:51PM |
B15.00008: Shaping Charge Excitations in Chiral Edge States with a Time-Dependent Gate Voltage Maciej Misiorny, Gwendal Fève, Janine Splettstoesser In this communication, we address the question of how the controlled injection of quantized charge excitations into a nanoscopic system is achieved, when a local emission is favored, but at the same time a strong size-confinement is hindered. Specifically, we propose an emission scheme, enabling a controlled production of noiseless, single-electron (and hole) current pulses by means of local time-dependent driving of a gate potential applied to a chiral edge transport channel. Employing a fully self-consistent treatment based on Floquet scattering theory, we study the effect of different voltage shapes and frequencies, as well as the role of the gate geometry on the injected signal. We highlight the impact of frequency-dependent screening on the process of shaping the current signal. The feasibility of creating true single-particle excitations with this method is confirmed by investigating the suppression of excess noise, which is otherwise created by additional electron-hole pair excitations in the current signal. Our analysis of the time-dependent transport in all driving-frequency regimes provides a clear recipe for the appropriate design of the gate-driving signal for local single-particle injection. |
Monday, March 5, 2018 12:51PM - 1:03PM |
B15.00009: Quantum dots formed in three-dimensional Dirac semimetal Cd3As2 nanowires Minkyung Jung, Kenji Yoshida, Mansoor Jalil, Naoto Nagaosa, Jungpil Seo, Kazuhiko Hirakawa Three-dimensional (3D) Dirac semimetals have attracted considerable attention owing to their exotic properties, both predicted in theory and recently demonstrated experimentally. Here, we demonstrate single quantum dots confined with two p-n junctions in 3D Dirac semimetal Cd3As2 nanowires under high magnetic fields. The device can be operated in two different regimes: (i) an n-type channel between n*-type leads underneath the source-drain contacts, creating an open regime (n*-n-n* configuration); (ii) a p-type channel in the middle of the nanowire, forming a p-type quantum dot (QD) (n*-p-n* configuration). At zero magnetic field, the quantum confinement effect vanishes in the n*-p-n* QD because the Dirac fermions penetrate p-n junctions with high transmission probability (Klein tunneling). However, the high magnetic fields bend the Dirac fermion trajectories at the p-n junction due to cyclotron motion, preventing the Klein tunneling. This results in a strong confinement at p-n junctions of Dirac materials. In this regime, the device shows clean Coulomb diamonds, indicating that a single QD is formed in a Dirac semimetal nanowire. |
Monday, March 5, 2018 1:03PM - 1:15PM |
B15.00010: Electronic Structure Engineering of Graphene Using Patterned Dielectric Superlattices Pilkyung Moon, Carlos Forsythe, Xiaodong Zhou, Takashi Taniguchi, Kenji Watanabe, Abhay Narayan, Mikito Koshino, Philip Kim, Cory Dean The ability to manipulate electrons with external electric fields provides a route to design electronic structures beyond the constraints of naturally occurring atomic crystals. We reported a new approach to fabricate high mobility superlattice devices by integrating dielectric patterning with atomically thin van der Waals materials [1]. |
Monday, March 5, 2018 1:15PM - 1:27PM |
B15.00011: Manipulation of The Electronic Transport Behavior in Monolayer Semiconductors with Dielectric Screening Iqbal Utama, Hans Kleemann, Wenyu Zhao, Feng Wang By virtue of their atomic-level thinness, the properties of layered 2D semiconductors and their heterostructures can differ substantially from their 3D counterparts. For instance, electronic properties of a monolayer semiconductor can be strongly influenced by the surrounding dielectric environment. We study the implications of the dielectric screening phenomenon in monolayer MoS2 by using electrical transport and scanning probe microscopy measurements. The possibility to tailor the electronic band properties of 2D semiconductors by using dielectric environment provides an alternative route to realize new electronic and optoelectronic device concepts. |
Monday, March 5, 2018 1:27PM - 1:39PM |
B15.00012: Spin Dependent Resonant Electron Tunneling through Graphene Double and Triple Barrier Junctions Shuanglong Liu, Yun-Peng Wang, James Fry, Hai-Ping Cheng We study spin-dependent electron transport properties of graphene double and triple barrier junctions via first-principles calculations. These 2D double barrier junctions consist of two graphene leads, two vacuum barriers, and a quantum well of zigzag graphene nanoribbon (ZGNR). Previous studies suggest that zigzag graphene edges are magnetic, which enables the spin-dependent electron transport investigated in our work. We observe resonant electron tunneling, and find that highly spin-polarized electric current can be obtained in such junctions. Furthermore, spin polarization of the electric current can be controlled by charge doping via gate voltage. When the vacuum barrier is replaced with monolayer boron nitride, non-resonant electron transmission increases since the barrier height decreases. We also tune the transport properties by changing the width of the quantum well and explore the properties of graphene triple barrier junctions. These double and triple barrier junctions may have potential application as a resonant tunneling diode in low dimensional electronics. |
Monday, March 5, 2018 1:39PM - 1:51PM |
B15.00013: Unique semiconducting behavior of Ultra-Thin Nickel Silicide Films Milad Yarali, Sara Pouladi, Shivkant Singh, Jae Hyun Ryou, Anastassios Mavrokefalos Nickel silicide (NiSi) has been extensively utilized in the photovoltaics mainly as adhesion promoter and as ohmic contact in silicide-on-Si Schottky-junction SCs.1 However, its lack of bandgap has restricted its applications in FETs, optoelectronics, thermoelectrics etc. 2,3 |
Monday, March 5, 2018 1:51PM - 2:03PM |
B15.00014: Nano-infrared imaging of surface plasmons in twisted bilayer graphene Fengrui Hu, Suprem R. Das, Yilong Luan, Ting Fung Chung, Yong Chen, Zhe Fei One of the major goals of the field of graphene plasmonics is to achieve functional nanophotonic circuits operating in the terahertz to infrared spectral regions. To achieve that, it is necessary to develop a large selection of graphene-based building blocks with plasmonic parameters that are stable even without continuous electrical gating. Here, we report the observation of tailored plasmonic responses in twisted bilayer graphene (tBLG) – two graphene layers stacked with a twist angle. Through near-field imaging of tBLG single crystals with a wide distribution of twist angles, we found that tBLG supports confined infrared plasmons that are sensitively dependent on the twist angle. More specifically speaking, as the twist angle varies from 0 to 30 degrees, the plasmon wavelength of tBLG increases and the plasmon damping rate decreases systematically. Further analysis and modeling indicate that the observed twist-angle-dependence of tBLG plasmons is mainly due to the Fermi-velocity renormalization, a unique characteristic of tBLG originated from the interlayer electron coupling. |
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