Cotunneling renormalization in carbon nanotube quantum dots

Kiršanskas, Gediminas; Paaske, Jens; Flensberg, Karsten

doi:10.1103/physrevb.86.075452

Cited by 5 publications

(9 citation statements)

References 34 publications

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“…Furthermore, if valley mixing originates from cotunneling (not only disorder as described above) different gatedependent shifts are predicted with the possibility of inelastic cotunneling lines crossing inside the Coulomb diamond (Kiršanskas, Paaske, and Flensberg, 2012). FIG.…”

Section: Methodsmentioning

confidence: 95%

Quantum transport in carbon nanotubes

et al. 2015

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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.

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Section: Methodsmentioning

confidence: 95%

Quantum transport in carbon nanotubes

et al. 2015

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“…Finally, the principal parts have the structure of the renormalization of the energy spectrum (Lamb shift 60 ) as can be seen from perturbation theory for energies 61 or real parts of self-energies in Green’s function formalism 62 . This suggest that this type of terms should be resummed to get an effective Hamiltonian in which new eigenspectrum of the quantum dots is obtained and the energy differences E b − E a are renormalized 63 64 .…”

Section: Resultsmentioning

confidence: 99%

Transport in serial spinful multiple-dot systems: The role of electron-electron interactions and coherences

Goldozian

Damtie

Kiršanskas

2016

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Quantum dots are nanoscopic systems, where carriers are confined in all three spatial directions. Such nanoscopic systems are suitable for fundamental studies of quantum mechanics and are candidates for applications such as quantum information processing. It was also proposed that linear arrangements of quantum dots could be used as quantum cascade laser. In this work we study the impact of electron-electron interactions on transport in a spinful serial triple quantum dot system weakly coupled to two leads. We find that due to electron-electron scattering processes the transport is enabled beyond the common single-particle transmission channels. This shows that the scenario in the serial quantum dots intrinsically deviates from layered structures such as quantum cascade lasers, where the presence of well-defined single-particle resonances between neighboring levels are crucial for device operation. Additionally, we check the validity of the Pauli master equation by comparing it with the first-order von Neumann approach. Here we demonstrate that coherences are of relevance if the energy spacing of the eigenstates is smaller than the lead transition rate multiplied by ħ.

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“…Strikingly, it can appear at voltages much larger or smaller than any of the naively expected energy scales, showing that it does not fit into the usual classification of resonances. All these features distinguish this resonance from known effects in the Coulomb blockade regime [24,27,28], including those due to inelastic cotunneling resolving excitations [29][30][31], the Kondo effect [32][33][34][35], and another zero-bias anomaly specific to QD spin valves [24,28]. The anomalous resonance we predict here relies on the coherent precession of a single spin that is driven by the Coulomb interaction-induced exchange field [35][36][37][38][39][40][41].…”

Section: Introductionmentioning

confidence: 95%

“…The anomalous resonance we predict here relies on the coherent precession of a single spin that is driven by the Coulomb interaction-induced exchange field [35][36][37][38][39][40][41]. The exchange field is a generic renormalization effect [31,[42][43][44][45] arising from quantum fluctuations of QD electrons into the attached ferromagnets. This leads to a spindependent level shift, i.e., an effective magnetic field, because the tunneling rates into the ferromagnets are spindependent.…”

Section: Introductionmentioning

confidence: 99%

Spin resonance without spin splitting

et al. 2015

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We predict that a single-level quantum dot without discernible splitting of its spin states develops a spin-precession resonance in charge transport when embedded into a spin valve. The resonance occurs in the generic situation of Coulomb blockaded transport with ferromagnetic leads whose polarizations deviate from perfect antiparallel alignment. The resonance appears when electrically tuning the interaction-induced exchange field perpendicular to one of the polarizations -- a simple condition relying on vectors in contrast to usual resonance conditions associated with energy splittings. The spin resonance can be detected by stationary dI/dV spectroscopy and by oscillations in the time-averaged current using a gate-pulsing scheme. The generic noncollinearity of the ferromagnets and junction asymmetry allow for an all-electric determination of the spin-injection asymmetry, the anisotropy of spin relaxation, and the magnitude of the exchange field. We also investigate the impact of a nearby superconductor on the resonance position. Our simplistic model turns out to be generic for a broad class of coherent few-level quantum systems.Comment: This is the version of the article published in Physical Review B in 201

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Cotunneling renormalization in carbon nanotube quantum dots

Cited by 5 publications

References 34 publications

Quantum transport in carbon nanotubes

Quantum transport in carbon nanotubes

Transport in serial spinful multiple-dot systems: The role of electron-electron interactions and coherences

Spin resonance without spin splitting

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