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K. M. Indlekofer

Publications and source records attributed to K. M. Indlekofer.

9 recordsLinked to original sources
arXiv2014

Numerical determination of a non-equilibrium many-body statistical operator for quasi-bound electrons in a gated nanowire system

We present a numerical approach to construct a non-equilibrium many-body statistical operator $\hatρ_\mathrm{rel}$ for an adaptive subspace of relevant quasi-bound electronic states in a semiconductor nanowire-based field-effect transistor (NWFET). As a constraint for $\hatρ_\mathrm{rel}$, we assume that the single-particle density matrix $ρ_1$ is a given quantity, resulting from a non-equilibrium Green's function (NEGF) calculation for the NWFET for a given set of applied voltages. Two different orthonormal (ON) eigenbases for $\hatρ_\mathrm{rel}$ are considered: (A) a Slater determinant basis of natural orbitals (eigenstates of $ρ_1$) and (B) the eigenbasis of the projected many-body Hamiltonian $\hat{H}_\mathrm{rel}$ within a relevant Fock subspace of the system. As for the eigenvalues $w_n$ of $\hatρ_\mathrm{rel}$, we furthermore assume that $w_n$ have a generalized Boltzmann form, parameterized by effective electrochemical potentials of natural orbitals and a given temperature. From the determined $\hatρ_\mathrm{rel}$, in turn, one can calculate expectation values for any many-body observable within the relevant subspace. As an example, we analyze the electron density and the covariance of the density-density correlation function for representative electronic preparations of the NWFET.

cond-mat.mes-hall↗
arXiv2007

Spatially resolved THz response as a characterization concept for nanowire FETs

In this paper, we propose a THz probe technique to obtain spatially resolved information about the electronic spectra inside nanowire-based FETs. This spectroscopic approach employs a segmented multi-gate design for the local detection of quantum transitions between few-electron states within the FET channel. We simulate the intra-band THz response of such devices by means of a many-body quantum approach, taking quantization and Coulomb interaction effects into account. The obtained simulation results demonstrate the capabilities of the proposed technique which go beyond the limitations of standard characterization methods.

cond-mat.other↗
arXiv2007

On the Possibility of Using Semiconductor Nanocolumns for the Realization of Quantum Bits

We propose the use of quantum dots formed in a semiconductor nanocolumn for the realization of charge or spin based quantum bits. The radial carrier confinement is achieved by employing conformal overgrowth, while multiple segmented gates are used to control the quantum dot properties. Different concepts for read-out and control are discussed. Furthermore, we assess which combinations of core nanowires and shell materials are feasible.

cond-mat.other↗
arXiv2006

Recursive approach to the calculation of a many-body basis in discrete electronic nanosystems

In this article, we describe a recursive method to construct a subset of relevant Slater-determinants for the use in many-body diagonalization schemes that will be employed in our forthcoming papers on the simulation of excited many-body states in discrete electronic nanosystems. The algorithm is intended for the realistic simulation of nanodevices which typically requires the consideration of a large number of single-particle basis states (typ. 256) and the calculation of a sufficient number (typ. a few 1000) of relevant excited many-body states.

cond-mat.other↗
arXiv2006

Quantum point contact due to Fermi-level pinning and doping profiles in semiconductor nanocolumns

We show that nanoscale doping profiles inside a nanocolumn in combination with Fermi-level pinning at the surface give rise to the formation of a saddle-point in the potential profile. Consequently, the lateral confinement inside the channel varies along the transport direction, yielding an embedded quantum point contact. An analytical estimation of the quantization energies will be given.

cond-mat.other↗
arXiv2006

Quantum confinement corrections to the capacitance of gated one-dimensional nanostructures

With the help of a multi-configurational Green's function approach we simulate single-electron Coulomb charging effects in gated ultimately scaled nanostructures which are beyond the scope of a selfconsistent mean-field description. From the simulated Coulomb-blockade characteristics we derive effective system capacitances and demonstrate how quantum confinement effects give rise to corrections. Such deviations are crucial for the interpretation of experimentally determined capacitances and the extraction of application-relevant system parameters.

cond-mat.other↗
arXiv2005

Quantum kinetic description of Coulomb effects in one-dimensional nano-transistors

In this article, we combine the modified electrostatics of a one-dimensional transistor structure with a quantum kinetic formulation of Coulomb interaction and nonequilibrium transport. A multi-configurational self-consistent Green's function approach is presented, accounting for fluctuating electron numbers. On this basis we provide a theory for the simulation of electronic transport and quantum charging effects in nano-transistors, such as gated carbon nanotube and whisker devices and one-dimensional CMOS transistors. Single-electron charging effects arise naturally as a consequence of the Coulomb repulsion within the channel.

cond-mat.other↗
arXiv2005

Simulation of quantum dead-layers in ferroelectric tunnel junctions

In this letter, we simulate electronic transport through a metal-ferroelectric-metal tunnel junction by use of a nonequilibrium Green's function approach. We show that quantum effects such as Friedel oscillations lead to deviations from the Thomas-Fermi screening model. As a consequence, we predict a bistable resistive switching effect, depending on the polarization state of the ferroelectric tunnel barrier.

cond-mat.other↗