S-matrix theory of single-channel ballistic transport through coupled quantum dots

I. Rotter; A. F. Sadreev

Home/Archive/arXiv

arXiv · cond-mat/0403184

S-matrix theory of single-channel ballistic transport through coupled quantum dots

I. Rotter·A. F. Sadreev

View original source ↗Read source document ↗Export metadata ↓

Abstract

We consider single-channel transmission through a double quantum dot system that consists of two single dots coupled by a wire of finite length L. In order to explain the numerically obtained results for a realistic double dot system we explore a simple model. It consists, as the realistic system, of two dots connected by a wire of length L. However, each of the two single dots is characterized by a few energy levels only, and the wire is assumed to have only one level whose energy depends on L. The transmission is described by using S-matrix theory. The model explains in particular the splitting of the resonant transmission peaks and the origin of the transmission zeros. The latter are independent of the length of the wire. When the transmission zeros of the single dots are of first order and both single dots are identical, those of the double dot are of second order. First-order transmission zeros cause phase jumps of the transmission amplitude by $π$, while there are no phase jumps related to second-order transmission zeros. In this latter case, a phase jump appears due to a resonance state whose decay width vanishes when crossing the energy of the transmission zero.

Explore related subjects

cond-mat.other cond-mat.mes-hall

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

I. Rotter, A. F. Sadreev. 2004-03-06. S-matrix theory of single-channel ballistic transport through coupled quantum dots. https://arxiv.org/abs/cond-mat/0403184

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Reversible and irreversible dynamical topological transitions of magnetic Hopfions

Magnetic Hopfions are three-dimensional (3D) topological solitons characterized by a nonzero Hopf invariant and offer a promising platform for 3D spintronics. While their static stabilization has been widely studied, their nonlinear dynamics under alternating magnetic (AM) fields remain largely unexplored. We show, using 3D micromagnetic simulations and analytical mode analysis, that an AM field drives two qualitatively distinct dynamical regimes of a confined magnetic Hopfion. In the weak-field regime, resonant excitation of intrinsic Hopfion modes induces a nonlinear instability and an irreversible topological reconfiguration from a Hopfion to a toron. In contrast, in the strong-field regime, the system undergoes reversible field-locked topological switching at GHz frequencies, with the magnetization periodically alternating between a topologically trivial ferromagnetic configuration and a Hopfion state. The switching pathway is selected by the driving frequency: a 2 GHz field drives a breathing pathway associated with the low-frequency collective response, whereas a 40 GHz field produces a nonresonant rotational pathway governed by strong Zeeman-torque-driven precession and field locking. These results identify field amplitude and frequency as independent control knobs and reveal that reversible Hopfion switching can arise either from nonlinear continuation of low-frequency collective motion or from nonresonant high-frequency field locking.

cond-mat.other↗

arXiv2026

Quantum Hamiltonian time crystals from covariant quantum Landau--Lifshitz--Gilbert relaxation

Classical Hamiltonian time crystals are constrained energy minima that move along symmetry orbits at frequencies set by Lagrange multipliers. We construct quantum counterparts by minimizing the energy over density matrices with fixed spectrum and charge expectations. A symmetry-covariant quantum Landau--Lifshitz--Gilbert equation selects them as periodic attractors, preserving the spectrum and fixing the multipliers dynamically. A chiral spin trimer motivated by Cu$_3$ molecular magnets realizes this motion at a prepared magnetization, without a Zeeman term.

cond-mat.other↗

arXiv2026

Quantum Metric Scaling and Its Exceptions in Classical Flat Bands

The quantum metric length has been proposed as the localization length scale in one-dimensional flat bands. Here, we study this quantum metric scaling and the exceptions to it in a classical flat band formed by a locally resonant mass--spring system. We find that the localization length follows the quantum metric length near the flat band but departs from this proportionality at the exact flat-band frequency. Selective mass disorder also produces divergent localization lengths or arbitrarily short tails near the flat-band frequency without changing the clean metric. These exceptions show that disorder can select localization scales beyond those predicted by the quantum metric alone.

cond-mat.other↗