scholarly journals Enabling Large-Scale Simulations of Quantum Transport with Manycore Computing

Electronics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 253
Author(s):  
Yosang Jeong ◽  
Hoon Ryu
Keyword(s):  
Quantum Transport ◽  
Large Scale ◽  
Performance Enhancement ◽  
Silicon Nanowire ◽  
Matrix Multiplication ◽  
Tight Binding ◽  
Optimization Techniques ◽  
Wide Energy Range ◽  
Processing Unit ◽  
Binding Model

The non-equilibrium Green’s function (NEGF) is being utilized in the field of nanoscience to predict transport behaviors of electronic devices. This work explores how much performance improvement can be driven for quantum transport simulations with the aid of manycore computing, where the core numerical operation involves a recursive process of matrix multiplication. Major techniques adopted for performance enhancement are data restructuring, matrix tiling, thread scheduling, and offload computing, and we present technical details on how they are applied to optimize the performance of simulations in computing hardware, including Intel Xeon Phi Knights Landing (KNL) systems and NVIDIA general purpose graphic processing unit (GPU) devices. With a target structure of a silicon nanowire that consists of 100,000 atoms and is described with an atomistic tight-binding model, the effects of optimization techniques on the performance of simulations are rigorously tested in a KNL node equipped with two Quadro GV100 GPU devices, and we observe that computation is accelerated by a factor of up to ∼20 against the unoptimized case. The feasibility of handling large-scale workloads in a huge computing environment is also examined with nanowire simulations in a wide energy range, where good scalability is procured up to 2048 KNL nodes.

THEORETICAL INVESTIGATIONS OF QUANTUM TRANSPORT THROUGH CARBON NANOTUBE DEVICES

2000 ◽  
Vol 07 (05n06) ◽  
pp. 637-642 ◽  
Author(s):  
C. ROLAND ◽  
M. BUONGIORNO NARDELLI ◽  
H. GUO ◽  
H. MEHREZ ◽  
J. TAYLOR ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Quantum Transport ◽  
Function Analysis ◽  
Tight Binding ◽  
Spin Valve ◽  
Superconducting Devices ◽  
Binding Model ◽  
Theoretical Investigations ◽  
Carbon Nanotube Devices

By combining a nonequilibrium Green's function analysis with a standard tight-binding model, we have investigated quantum transport through carbon nanotube devices. For finite-sized nanotubes, transport is dominated by resonant tunneling, with the conductance being strongly dependent on the length of the nanotubes. Turning to nanotube devices, we have investigated spin-coherent transport in ferromagnetic–nanotube–ferromagnetic devices and nanotube-superconducting devices. The former shows a significant spin valve effect, while the latter is dominated by resonant Andreev reflections. In addition, we discuss AC transport through carbon nanotubes and the role of photon-assisted tunneling.

scholarly journals Large-scale tight-binding simulations of quantum transport in ballistic graphene

2018 ◽  
Vol 30 (36) ◽  
pp. 364001 ◽  
Author(s):  
Gaetano Calogero ◽  
Nick R Papior ◽  
Peter Bøggild ◽  
Mads Brandbyge
Keyword(s):  
Quantum Transport ◽  
Large Scale ◽  
Tight Binding

scholarly journals QUANTUM TRANSPORT THROUGH SINGLE PHENALENYL MOLECULE: EFFECT OF INTERFACE STRUCTURE

2007 ◽  
Vol 06 (06) ◽  
pp. 415-422 ◽  
Author(s):  
SANTANU K. MAITI
Keyword(s):  
Quantum Transport ◽  
Electronic Transport ◽  
Coupling Strength ◽  
Tight Binding ◽  
Interface Structure ◽  
Function Technique ◽  
Tight Binding Model ◽  
Parametric Approach ◽  
Binding Model ◽  
Molecular Bridge

The electronic transport characteristics through a single phenalenyl molecule sandwiched between two metallic electrodes are investigated by using Green's function technique. A parametric approach, based on the tight-binding model, is used to study the transport characteristics through such molecular bridge system. The electronic transport properties are significantly influenced by (a) the molecule-to-electrodes interface structure and (b) the molecule-to-electrodes coupling strength.

A self-consistent tight binding model for hydrocarbon systems: application to quantum transport simulation

2004 ◽  
Vol 16 (39) ◽  
pp. 6851-6866 ◽  
Author(s):  
D A Areshkin ◽  
O A Shenderova ◽  
J D Schall ◽  
S P Adiga ◽  
D W Brenner
Keyword(s):  
Quantum Transport ◽  
Tight Binding ◽  
Tight Binding Model ◽  
Binding Model ◽  
Transport Simulation ◽  
Self Consistent

scholarly journals Precise programmable quantum simulations with optical lattices

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Xingze Qiu ◽  
Jie Zou ◽  
Xiaodong Qi ◽  
Xiaopeng Li
Keyword(s):  
Large Scale ◽  
Optical Potential ◽  
Optical Lattices ◽  
High Efficiency ◽  
Tight Binding ◽  
Binding Model ◽  
Wannier Functions ◽  
Quantum Simulations ◽  
Binding Models ◽  
High Band

Abstract We present an efficient approach to precisely simulate tight binding models with optical lattices, based on programmable digital-micromirror-device (DMD) techniques. Our approach consists of a subroutine of Wegner-flow enabled precise extraction of a tight-binding model for a given optical potential, and a reverse engineering step of adjusting the potential for a targeting model, for both of which we develop classical algorithms to achieve high precision and high efficiency. With renormalization of Wannier functions and high band effects systematically calibrated in our protocol, we show the tight-binding models with programmable onsite energies and tunnelings can be precisely simulated with optical lattices integrated with the DMD techniques. With numerical simulation, we demonstrate that our approach would facilitate quantum simulation of localization physics with adequate programmability and atom-based boson sampling for illustration of quantum computational advantage. We expect this approach would pave a way towards large-scale and precise programmable quantum simulations based on optical lattices.

Review on Performance Enhancement Studies on Solar Dryer

2015 ◽  
Vol 787 ◽  
pp. 129-133
Author(s):  
A.S. Ramana ◽  
T.V. Ashokumaar ◽  
K. Vignesh
Keyword(s):  
Solar Energy ◽  
Large Scale ◽  
Performance Enhancement ◽  
Cost Effective ◽  
Optimization Techniques ◽  
Heating Process ◽  
Thermal Systems ◽  
Drying Time ◽  
Solar Dryer ◽  
Drying System

Abundant availability of solar energy and fast depleting fossil fuel reserves have necessitated deployment of large scale solar thermal systems for meeting the space heating, process heating and drying requirements. Researchers worldwide have focused on developing energy efficient dryer capable of enhancing product quality, reduced drying time, high throughput, minimal pre-treatments prior to drying with less energy loss in cost effective way. The present paper surveys literature on performance enhancement studies on solar dryer with a thrust on energy efficiency improvements in solar air collector and a multipurpose solar drying system. The effect of adoption of absorber plate with different types of fins, design modifications, CFD based optimization techniques and incorporation of storage materials have been reviewed. A dual-purpose solar water heating and drying system with phase change material (PCM) is suggested for effective harnessing of solar energy.

scholarly journals Quantum Transport Properties of Two-Dimensional Quantum Lattices under Synthetic Magnetic

2019 ◽  
Vol 82 ◽  
pp. 21-33
Author(s):  
Pubudu G. Wijesinghe ◽  
K.A.I.L. Wijewardena Gamalath
Keyword(s):  
Band Structure ◽  
Transport Properties ◽  
Lattice Constant ◽  
Quantum Transport ◽  
Tight Binding ◽  
Flat Band ◽  
Two Dimensional ◽  
Kagome Lattice ◽  
Binding Model ◽  
Kagomé Lattice

Motivated by recent experimental progress, we study the quantum transport properties of two-dimensional electron gases under high perpendicular magnetic fields. We use a simple tight-binding model to model the system and open-source software to simulate quantum electronic transport properties such as band structure variations and conductance-flux relationships in such systems. Dependence of quantum transport properties on two-dimensional square, triangular and kagome lattice shapes were studied adding a Gaussian noise to account for the impurities. Numerical simulations are presented to predict the emergence of physical effects related to quantum Hall effect, such as the existence of Landau levels and edge states. The kagome lattice exhibits a different band structure giving rise to a flat band, due to its trihexagonal geometry. The peak conductance value increases with decreasing lattice constant due to higher transmission probability. The transport properties vary significantly with lattice geometries, both with the lattice type and the lattice constant.

scholarly journals Cobalt-based magnetic Weyl semimetals with high-thermodynamic stabilities

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Wei Luo ◽  
Yuma Nakamura ◽  
Jinseon Park ◽  
Mina Yoon
Keyword(s):  
Tight Binding ◽  
Three Dimensional ◽  
Interlayer Coupling ◽  
First Principles Calculation ◽  
Optimization Approach ◽  
Binding Model ◽  
Nodal Lines ◽  
Weyl Semimetal ◽  
Topological Quantum ◽  
First Time

AbstractRecent experiments identified Co3Sn2S2 as the first magnetic Weyl semimetal (MWSM). Using first-principles calculation with a global optimization approach, we explore the structural stabilities and topological electronic properties of cobalt (Co)-based shandite and alloys, Co3MM’X2 (M/M’ = Ge, Sn, Pb, X = S, Se, Te), and identify stable structures with different Weyl phases. Using a tight-binding model, for the first time, we reveal that the physical origin of the nodal lines of a Co-based shandite structure is the interlayer coupling between Co atoms in different Kagome layers, while the number of Weyl points and their types are mainly governed by the interaction between Co and the metal atoms, Sn, Ge, and Pb. The Co3SnPbS2 alloy exhibits two distinguished topological phases, depending on the relative positions of the Sn and Pb atoms: a three-dimensional quantum anomalous Hall metal, and a MWSM phase with anomalous Hall conductivity (~1290 Ω−1 cm−1) that is larger than that of Co2Sn2S2. Our work reveals the physical mechanism of the origination of Weyl fermions in Co-based shandite structures and proposes topological quantum states with high thermal stability.

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