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Full-Text Articles in Quantum Physics

Universal Electric Current Of Interacting Resonant-Level Models With Asymmetric Interactions: An Extension Of The Landauer Formula, Akinori Nishino, Naomichi Hatano, Gonzalo Ordonez Jan 2015

Universal Electric Current Of Interacting Resonant-Level Models With Asymmetric Interactions: An Extension Of The Landauer Formula, Akinori Nishino, Naomichi Hatano, Gonzalo Ordonez

Scholarship and Professional Work - LAS

We study the electron transport in open quantum-dot systems described by the interacting resonant-level models with Coulomb interactions. We consider the situation in which the quantum dot is connected to the left and right leads asymmetrically. We exactly construct many-electron scattering eigenstates for the two-lead system, where two-body bound states appear as a consequence of one-body resonances and the Coulomb interactions. By using an extension of the Landauer formula, we calculate the average electric current for the system under bias voltages in the first order of the interaction parameters. Through a renormalization-group technique, we arrive at the universal electric current, …


Optically Tunable Bound States In The Continuum, Yingyue Boretz, Gonzalo Ordonez, Satoshi Tanaka, Tomio Petrosky Jan 2014

Optically Tunable Bound States In The Continuum, Yingyue Boretz, Gonzalo Ordonez, Satoshi Tanaka, Tomio Petrosky

Scholarship and Professional Work - LAS

We demonstrate the existence of tunable bound states in the continuum (BICs) in a one-dimensional quantum wire with two impurities induced by an intense monochromatic radiation field. We find that there is an interesting type of BIC due to the Fano interference between two optical transition channels, in addition to the ordinary BIC due to geometrical interference between electron wave functions emitted by impurities. In both cases the BIC can be achieved by tuning the frequency of the radiation field. Evidence of the BIC can be obtained by observing the absorption rate of a probe photon.


Time-Reversal Symmetric Resolution Of Unity Without Background Integrals In Open Quantum Systems, Naomichi Hatano, Gonzalo Ordonez Jan 2014

Time-Reversal Symmetric Resolution Of Unity Without Background Integrals In Open Quantum Systems, Naomichi Hatano, Gonzalo Ordonez

Scholarship and Professional Work - LAS

We present a new complete set of states for a class of open quantum systems, to be used in expansion of the Green’s function and the time-evolution operator. A remarkable feature of the complete set is that it observes time-reversal symmetry in the sense that it contains decaying states (resonant states) and growing states (anti-resonant states) parallelly. We can thereby pinpoint the occurrence of the breaking of time-reversal symmetry at the choice of whether we solve Schrödinger equation as an initial-condition problem or a terminal-condition problem. Another feature of the complete set is that in the subspace of the central …


Quantum Diffusion-Limited Aggregation, David Bradley Johnson Aug 2011

Quantum Diffusion-Limited Aggregation, David Bradley Johnson

Undergraduate Honors Thesis Collection

Though classical random walks have been studied for many years, research concerning their quantum analogues, quantum random walks, has only come about recently. Numerous simulations of both types of walks have been run and analyzed, and are generally well-understood. Research pertaining to one of the more important properties of classical random walks, namely, their ability to build fractal structures in diffusion-limited aggregation, has been particularly noteworthy. However, nobody has yet pursued this avenue of research in the realm of quantum random walks. The study of random walks and the structures they build has various applications in materials science. Since all …


Modeling Bound States In The Continuum For Multiple Electrons In A Quantum Dot Pair, Thomas Ian Tuegel Apr 2010

Modeling Bound States In The Continuum For Multiple Electrons In A Quantum Dot Pair, Thomas Ian Tuegel

Undergraduate Honors Thesis Collection

The bound eigenstates of an electron inside a pair of quantum dots embedded on an infinite quantum wire are examined using the method of particular solutions. The eigenstates of a two-electron system in the same structure are examined perturbatively using wavefunction expansions for the one-electron eigenstates. The stability of the two-electron eigenstates is evaluated and compared with other theoretical results. It is found that stable bound states in the continuum exist for two electrons confined to this geometry.


Phase Diagram Of The One-Dimensional Hubbard-Holstein Model At Half And Quarter Filling, Rahul Hardikar, R. T. Clay Jan 2007

Phase Diagram Of The One-Dimensional Hubbard-Holstein Model At Half And Quarter Filling, Rahul Hardikar, R. T. Clay

Scholarship and Professional Work - LAS

The Hubbard-Holstein model is one of the simplest to incorporate both electron-electron and electron-phonon interactions. In one dimension at half filling, the Holstein electron-phonon coupling promotes on-site pairs of electrons and a Peierls charge-density wave, while the Hubbard on-site Coulomb repulsion U promotes antiferromagnetic correlations and a Mott insulating state. Recent numerical studies have found a possible third intermediate phase between Peierls and Mott states. From direct calculations of charge and spin susceptibilities, we show that (i) as the electron-phonon coupling is increased, first a spin gap opens, followed by the Peierls transition. Between these two transitions, the metallic intermediate …


Electron Trapping In A One-Dimensional Semiconductor Quantum Wire With Multiple Impurities, S. Tanaka, S. Garmon, Gonzalo Ordonez, T. Petrosky Jan 2007

Electron Trapping In A One-Dimensional Semiconductor Quantum Wire With Multiple Impurities, S. Tanaka, S. Garmon, Gonzalo Ordonez, T. Petrosky

Scholarship and Professional Work - LAS

We demonstrate the trapping of a conduction electron between two identical adatom impurities in a one-dimensional semiconductor quantum-dot array system (quantum wire). Bound steady states arise even when the energy of the adatom impurity is located in the continuous one-dimensional energy miniband. The steady state is a realization of the bound state in continuum (BIC) phenomenon first proposed by von Neuman and Wigner [Phys. Z. 30, 465 (1929)]. We analytically solve the dispersion equation for this localized state, which enables us to reveal the mechanism of the BIC. The appearance of the BIC state is attributed to the quantum …


Bound States In The Continuum In Quantum-Dot Pairs, Gonzalo Ordonez, Kyungsun Na, Sungyun Kim Jan 2006

Bound States In The Continuum In Quantum-Dot Pairs, Gonzalo Ordonez, Kyungsun Na, Sungyun Kim

Scholarship and Professional Work - LAS

It is shown that for two open quantum dots connected by a wire, “bound states in the continuum” of a single electron are formed at nearly periodic distances between the dots. This is due to Fabry-Pérot interference between quasibound states in each dot. The bound states are nonlocal, describing the electron trapped in both dots at the same time. Theoretical and numerical results show that trapped states exist even if the wire connecting the dots is relatively long.


Intermediate Phase Of The One Dimensional Half-Filled Hubbard-Holstein Model, R. T. Clay, Rahul Hardikar Jan 2005

Intermediate Phase Of The One Dimensional Half-Filled Hubbard-Holstein Model, R. T. Clay, Rahul Hardikar

Scholarship and Professional Work - LAS

We present a numerical study of the Hubbard-Holstein model in one dimension at half filling, including finite-frequency quantum phonons. At half filling, the effects of the electron-phonon and electron-electron interactions compete with the Holstein phonon coupling acting as an effective negative Hubbard on-site interaction U that promotes on-site electron pairs and a Peierls charge-density wave state. Most previous work on this model has assumed that only Peierls or Mott phases are possible at half filling. However, there has been speculation that a third metallic phase exists between the Peierls and Mott phases. We confirm the intermediate phase, and show that …