Search query: Quantum transport in carbon nanotubes

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abstract: Carbon nanotubes are a versatile material in which many aspects of condensed matter physics come together. Recent discoveries have uncovered new phenomena that completely change our understanding of transport in these devices, especially the role of the spin and valley degrees of freedom. This review describes the modern understanding of transport through nanotube devices. Unlike in conventional semiconductors, electrons in nanotubes have two angular momentum quantum numbers, arising from spin and valley freedom. The interplay between the two is the focus of this review. The energy levels associated with each degree of freedom, and the spin orbit coupling between them, are explained, together with their consequences for transport measurements through nanotube quantum dots. In double quantum dots, the combination of quantum numbers modifies the selection rules of Pauli blockade. This can be exploited to read out spin and valley qubits and to measure the decay of these states through coupling to nuclear spins and phonons. A second unique property of carbon nanotubes is that the combination of valley freedom and electron electron interactions in one dimension strongly modifies their transport behavior. Interaction between electrons inside and outside a quantum dot is manifested in SU(4) Kondo behavior and level renormalization. Interaction within a dot leads to Wigner molecules and more complex correlated states. This review takes an experimental perspective informed by recent advances in theory. As well as the well understood overall picture, open questions for the field are also clearly stated. These advances position nanotubes as a leading system for the study of spin and valley physics in one dimension where electronic disorder and hyperfine interaction can both be reduced to a low level.
author_names: E A Laird

Ferdinand Kuemmeth

Gary A Steele

K Grove-Rasmussen

Jesper Nygaard

Karsten Flensberg

L P Kouwenhoven
title: Quantum transport in carbon nanotubes
year: 2015

abstract: Abstract The renormalization decimation algorithm (RDA) of Lopez Sancho et al. is used in quantum transport theory to calculate bulk and surface Green's functions. We derive an improved version of the RDA for the case of very long quasi one dimensional unit cells (in transport direction) This covers not only long unit cells but also supercell like calculations for structures with disorder or defects. In such large systems, short range interactions lead to sparse real space Hamiltonian matrices. We show how this and a corresponding subdivision of the unit cell in combination with the decimation technique can be used to reduce the calculation time. Within the resulting algorithm, separate RDA calculations of much smaller effective Hamiltonian matrices must be done for each Green's function, which enables the treatment of systems too large for the common RDA. Finally, we discuss the performance properties of our improved algorithm as well as some exemplary results for chiral carbon nanotubes.
author_names: Fabian Teichert

Andreas Zienert

Jorg Schuster

Michael Schreiber
title: An improved Green's function algorithm applied to quantum transport in carbon nanotubes
venue: Computational Materials Science
year: 2019

abstract: Carbon nanotubes are of central importance for applications in nano electronics thanks to their exceptional transport properties. They can be used as sensors, for example in biological applications, provided that they are functionalized to detect specific molecules. Due to their one dimensional geometry the carbon nanotubes are very sensitive to the phenomenon of Anderson localization and it is therefore essential to know how the functionalization modifies their conduction properties and if they remain good conductors. Here we present a study of the quantum localization induced by functionalization in metallic single walled carbon nanotubes (SWCNT) with circumferences up to 15\,nm. We consider resonant and non resonant adsorbates that represent two types of covalently functionalized groups with strong and moderate scattering properties. The present study provides a detailed analysis of the localization behaviour and shows that the localization length can decrease down to 20 50\,nm at concentrations of about 1 percent of adsorbates. On this basis we discuss the possible electronic transport mechanisms which can be either metallic like or insulating like with variable range hopping.
author_names: Ghassen Jemai

Jouda Jemaa Khabthani

Guy Trambly de Laissardiere

Didier Mayou
title: Quantum localization and electronic transport in covalently functionalized carbon nanotubes.
venue: Journal of physics. Condensed matter an Institute of Physics journal
year: 2019

abstract: We report on quantum transport measurements of a carbon nanotube (CNT) quantum dot that is functionalized with magnetic {Mn4} complexes. The coupling between the spin 5/2 MnII ions within each {Mn4} complex is predominantly antiferromagnetic. Coulomb diamond measurements at T 4 K reveal that the covalent attachment of the complexes to the CNT framework has only little influence on the carbon nanotube quantum dot. Surprisingly, a strong increase of noise is observed upon cooling the sample to T 30 mK. Time traces of the current taken at a diamond edge reveal a random telegraph signal. We attribute this to fluctuations of molecular spin states of the attached {Mn4} complexes.
author_names: Michael Schnee

Claire Besson

Robert Frielinghaus

Christian Lurz

Paul Kogerler

Claus Michael Schneider

Carola Meyer
title: Quantum transport in carbon nanotubes covalently functionalized with magnetic molecules
year: 2016

abstract: We derive an improved version of the renormalization decimation algorithm (RDA) of L\'opez Sancho, which is used in quantum transport theory to calculate the bulk and the surface Green's function of a device. We consider the case of very long unit cells (in transport direction) This covers not only long unit cells itself but also supercell like calculations for defective structures. For such large systems, short range interactions lead to a sparse real space Hamiltonian matrix. We show how this and a corresponding subdivision of the unit cell in combination with the decimation technique can be used to previously reduce the system size. The result are separate RDA calculation of much smaller effective Hamiltonian matrices for each Green's function. Finally, we present the performance properties of our improved algorithm as well a some exemplary results for chiral carbon nanotubes.
author_names: Fabian Teichert

Andreas Zienert

Jorg Schuster

Michael Schreiber
title: An improved scheme for calculating the bulk and surface Green's functions within quantum transport theory for systems with long unit cells: Application to carbon nanotubes
year: 2018

abstract: In the last twenty years, due to technological advances, it has become possible to build, manipulate and observe nanometer structures and so their dimensions are intermediate between the microscopic and macroscopic. These new systems present novel features and have originated the new field of mesoscopic physics As for the transport properties the mesoscopic conductors do not have ohmic behaviour and the free mean path of electrons is longer than the conductor length in some systems. In this case the conductor is called ballistic, i. e. the electron can travel without scattering in the bulk of the conductor. Another significant consequence of the conductor low dimensionality is that its conductanceG I /V is quantized. The current approach to describe these phenomena is the transmission formalism introduced by Landauer: the current through a conductor is given by the probability that an electron can transmit through it [1] Carbon nanotubes (CNT) which are cylindrical macromolecules formed by periodic hexagonal structures of carbon atoms and typically 1 to 5 nm wide and 1 to 10mm long, should be in ideal systems to proof the theories about the mesoscopic transport.The nature of the electronic transport in CNT is intriguing and still a matter of debate, and only a few experiments have shown the conductance quantization in CNT [2, 3] In this work we present new transport data on carbon double wall nanotubes (DWNT) by means of the mechanically controllable break junction (MCBJ) technique [4] We assume that scattering in the bulk is negligible and the number of channels determines the average conductance in the ballistic regime. A major conclusion of our work is the realization that actually there are two types of ballistic pathways in carbon nanotubes networks. Further theoretical and experimental studies at high voltages seems necessary to better understand the DWNT properties.
author_names: Mark Baxendale

Mauro Melli

I E Pollini
title: Quantum transport in carbon nanotubes
year: 2005

abstract: We study the transport properties of single walled carbon nanotubes (SWCNTs) using the nonequilibrium Green's function method based on first principles calculations. We compared three SWCNTs with different chiralities (3, 3) (5, 0) and (4, 2) and found that the thermal conductance varies significantly with the chirality, especially at low temperatures. Such differences are attributed to the dependence on the chirality of the frequency of the lowest optical mode and phonon phonon interaction with the semi infinite leads. To obtain accurate low vibrational frequencies, a force constant correction based on the Lagrange undetermined multiplier method was employed. The phonon phonon interaction was analyzed in terms of the projection of the phonon coupling with the semi infinite leads onto the normal modes of the center region. Our result indicates that high optical mode frequency and weak phonon coupling on the armchair (3, 3) SWCNT are the origin of the long quantized plateau found in the experimental thermal conductance.
author_names: Tomoyuki Hata

Hiroki Kawai

Tatsuhiko Ohto

Koichi Yamashita
title: Chirality dependence of quantum thermal transport in carbon nanotubes at low temperatures: a first principles study.
venue: The Journal of chemical physics
year: 2013

abstract: Abstract MnO quantum dots homogenously embedded in carbon nanotubes (denoted as MnO QDs@CNTs) were prepared via a scalable electrospinning technique with LiN 3 serving as poregen agent. The strong N 2 evolution resulting from the explosive decomposition of the porogen LiN 3 and oxidation diffusion of MnCl 2 during the heat treatment are found to be responsible for the formation of the hierarchy structure. As binder free anodes, the composite networks displayed extraordinary LIBs performance with good reversible capacity (as high as ~1100 mAh g 1 at 100 mA g 1 high coulombic efficiency, outstanding rate capability and superior cyclic performance (nearly no capacity fading after 200 cycles at a high current density of 3000 mA g 1 owing to the unique combination of ultra small MnO QDs and stable CNTs with excellent transport properties. This shows MnO QDs@CNTs composites are almost the most efficient MnO based anode materials for LIBs so far.
author_names: Lijun Zhang

Guanglin Xia

Yuqin Huang

Chenyun Wei

Yiwei Yu

Dalin Sun

Xuebin Yu
title: MnO quantum dots embedded in carbon nanotubes as excellent anode for lithium ion batteries
year: 2018

abstract: Abstract We present a tutorial introduction into the structure and electronic properties of carbon nanotubes which may serve as an entry point into the literature on the field. Some of the original experiments in the field are selected to illustrate the richness of quantum transport in single and multi wall carbon nanotubes.
author_names: Elsa Thune

Christoph Strunk
title: Quantum Transport in Carbon Nanotubes
year: 2006

abstract: We study two conceptually different regimes of electronic transport in carbon nanotubes. In the first part, we analyse spin transport across a carbon nanotube quantum dot coupled to ferromagnetic leads. More specifically, we account for charge fluctuations between the dot and contacts that are sensitive to the ferromagnetic properties of the contacts. This enables us to analyse specific features observed in the differential conductance and the tunnelling magneto resistance data. The agreement between the model output and the experimental data is on a qualitative level. In the second part we study electronic wave interference phenomena, similar to the Fabry Perot interference in optics. We find that the interplay of the trigonal warping of the graphene lattice and the geometry of the carbon nanotube are the key to the interpretation of a superimposed modulation of the differential conductance. We provide a detailed analysis of experimental observations in the transparent regime and extract the chiral angle of the carbon nanotube under investigation.
author_names: Alois Dirnaichner
title: Charge and spin transport in carbon nanotubes:From Coulomb blockade to Fabry Perot interference
year: 2017