First-principles time-dependent quantum transport theory

In addition to the well-known anti-ferromagnetic and ferromagnetic edge states in zigzag graphene nanoribbons (GNR), we find that there also exist some excited spin density wave (ESDW) states, the energies of which are close to the anti-ferromagnetic state (ground state). We thus argue that these ESDW states may coexist in experiment. Our numerical results from the self-consistent mean-field method as well as the first-principles calculations indicate that the allowed ESDWs are commensurate; and their dispersion curves are linear in the long wave limit. The coupling of the two edge portions in an ESDW becomes very weak in a wide GNR, in which case these ESDW portions may have different phases. Finally our calculations in the non-equilibrium Green's function theory combined with the Hubbard model show that these ESDW states can also exist in some localized (middle or terminal) region of GNR.

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“…The integral in equation (9) can be effective evaluated by the residue theorem [31,32]. The details can be seen in appendix A and [33,34].…”

Section: Negf Theorymentioning

confidence: 99%

Excited spin density waves in zigzag graphene nanoribbons

2018

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“…The green dashed curves are calculated using HEOM approach with the WBL approximation. 22 The red dotted horizontal lines are the steady state current calculated by Landauer formula from non-WBL self-consistent calculation. The good agreement between the steady state currents obtained from selfconsistent calculation (dotted curves) and time-dependent simulation (solid curves) validates the correctness of our method and verifies our scheme as beyond the WBL.…”

Section: Resultsmentioning

confidence: 99%

“…This can be seen from their definitions in Eqs. (20) and (22). The locality of ARSDM keeps unchanged under time propagation, which can be checked from the HEOM.…”

Section: Computational Complexitymentioning

confidence: 98%

“…If the wide-band limit (WBL) approximation a) Electronic mail: ghc@everest.hku.hk is made, the RSDM based HEOM can be closed at 1 st tier. 10,22 Beyond the WBL, the RSDM based HEOM have been applied to simulate time-dependent quantum transport in tightbinding model system. 23,24 However, in the derivation of RSDM based HEOM, a localized orthonormal basis set is assumed.…”

Section: Introductionmentioning

confidence: 99%

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Time-dependent density functional theory quantum transport simulation in non-orthogonal basis

Kwok

Xie

Yam

et al. 2013

The Journal of Chemical Physics

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Real-time, local basis-set implementation of time-dependent density functional theory for excited state dynamics simulations A model study of quantum dot polarizability calculations using time-dependent density functional methods Basing on the earlier works on the hierarchical equations of motion for quantum transport, we present in this paper a first principles scheme for time-dependent quantum transport by combining timedependent density functional theory (TDDFT) and Keldysh's non-equilibrium Green's function formalism. This scheme is beyond the wide band limit approximation and is directly applicable to the case of non-orthogonal basis without the need of basis transformation. The overlap between the basis in the lead and the device region is treated properly by including it in the self-energy and it can be shown that this approach is equivalent to a lead-device orthogonalization. This scheme has been implemented at both TDDFT and density functional tight-binding level. Simulation results are presented to demonstrate our method and comparison with wide band limit approximation is made. Finally, the sparsity of the matrices and computational complexity of this method are analyzed.

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“…This method has been successfully employed in simulations of current carrying molecular junctions. [36][37][38] A larger 6-311+ G * basis set is used for the dithiol part, for better description of the charged states. For the doublet anion and cation, calculated states with large spin contaminations were filtered out (a threshold of |⟨S 2 ⟩ − 3/4| > 1.0 was used where 3/4 is the reference value for a doublet state).…”

Section: Coherent 2d Signal Of Benzene-14-dithiolmentioning

confidence: 99%

Coherent (photon) vs incoherent (current) detection of multidimensional optical signals from single molecules in open junctions

Agarwalla

Harbola

Hua

et al. 2015

The Journal of Chemical Physics

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The nonlinear optical response of a current-carrying single molecule coupled to two metal leads and driven by a sequence of impulsive optical pulses with controllable phases and time delays is calculated. Coherent (stimulated, heterodyne) detection of photons and incoherent detection of the optically induced current are compared. Using a diagrammatic Liouville space superoperator formalism, the signals are recast in terms of molecular correlation functions which are then expanded in the many-body molecular states. Two dimensional signals in benzene-1,4-dithiol molecule show cross peaks involving charged states. The correlation between optical and charge current signal is also observed. C 2015 AIP Publishing LLC. [http://dx

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First-principles time-dependent quantum transport theory

Cited by 61 publications

References 24 publications

Excited spin density waves in zigzag graphene nanoribbons

Excited spin density waves in zigzag graphene nanoribbons

Time-dependent density functional theory quantum transport simulation in non-orthogonal basis

Coherent (photon) vs incoherent (current) detection of multidimensional optical signals from single molecules in open junctions

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