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Lozano-Negro FS, Ferreyra-Ortega MA, Bendersky D, Fernández-Alcázar L, Pastawski HM. Simulating a catalyst induced quantum dynamical phase transition of a Heyrovsky reaction with different models for the environment. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:214006. [PMID: 35196264 DOI: 10.1088/1361-648x/ac57d6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 02/23/2022] [Indexed: 06/14/2023]
Abstract
Through an appropriate election of the molecular orbital basis, we show analytically that the molecular dissociation occurring in a Heyrovsky reaction can be interpreted as a quantum dynamical phase transition, i.e., an analytical discontinuity in the molecular energy spectrum induced by the catalyst. The metallic substrate plays the role of an environment that produces an energy uncertainty on the adatom. This broadening induces a critical behavior not possible in a quantum closed system. We use suitable approximations on symmetry, together with both Lanczos and canonical transformations, to give analytical estimates for the critical parameters of molecular dissociation. This occurs when the bonding to the surface is2times the molecular bonding. This value is slightly weakened for less symmetric situations. However simple, this conclusion involves a high order perturbative solution of the molecule-catalyst system. This model is further simplified to discuss how an environment-induced critical phenomenon can be evaluated through an idealized perturbative tunneling microscopy set-up. In this case, the energy uncertainties in one or both atoms are either Lorentzian or Gaussian. The former results from the Fermi golden rule, i.e., a Markovian approximation. The Gaussian uncertainty, associated with non-Markovian decoherent processes, requires the introduction of a particular model of a spin bath. The partially coherent tunneling current is obtained from the generalized Landauer-Büttiker equations. The resonances observed in these transport parameters reflect, in many cases, the critical properties of the resonances in the molecular spectrum.
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Affiliation(s)
- Fabricio S Lozano-Negro
- Instituto de Física Enrique Gaviola (CONICET-UNC) and Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, Av. Medina Allende s/n, Córdoba, Córdoba 5000, Argentina
| | - Marcos A Ferreyra-Ortega
- Instituto de Física Enrique Gaviola (CONICET-UNC) and Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, Av. Medina Allende s/n, Córdoba, Córdoba 5000, Argentina
| | - Denise Bendersky
- Instituto de Física Enrique Gaviola (CONICET-UNC) and Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, Av. Medina Allende s/n, Córdoba, Córdoba 5000, Argentina
| | - Lucas Fernández-Alcázar
- Instituto de Física Enrique Gaviola (CONICET-UNC) and Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, Av. Medina Allende s/n, Córdoba, Córdoba 5000, Argentina
| | - Horacio M Pastawski
- Instituto de Física Enrique Gaviola (CONICET-UNC) and Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, Av. Medina Allende s/n, Córdoba, Córdoba 5000, Argentina
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2
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Deghi SE, Fernández-Alcázar LJ, Pastawski HM, Bustos-Marún RA. Current-induced forces in single-resonance systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:175303. [PMID: 33530077 DOI: 10.1088/1361-648x/abe266] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 02/02/2021] [Indexed: 06/12/2023]
Abstract
In recent years, there has been an increasing interest in nanoelectromechanical devices, current-driven quantum machines, and the mechanical effects of electric currents on nanoscale conductors. Here, we carry out a thorough study of the current-induced forces and the electronic friction of systems whose electronic effective Hamiltonian can be described by an archetypal model, a single energy level coupled to two reservoirs. Our results can help better understand the general conditions that maximize the performance of different devices modeled as a quantum dot coupled to two electronic reservoirs. Additionally, they can be useful to rationalize the role of current-induced forces in the mechanical deformation of one-dimensional conductors.
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Affiliation(s)
- Sebastián E Deghi
- Instituto de Física Enrique Gaviola and Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, 5000, Argentina
| | - Lucas J Fernández-Alcázar
- Wave Transport in Complex Systems Lab, Department of Physics, Wesleyan University, Middletown, CT-06459, United States of America
| | - Horacio M Pastawski
- Instituto de Física Enrique Gaviola and Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, 5000, Argentina
| | - Raúl A Bustos-Marún
- Instituto de Física Enrique Gaviola and Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, 5000, Argentina
- Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, 5000, Argentina
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Sánchez CM, Chattah AK, Wei KX, Buljubasich L, Cappellaro P, Pastawski HM. Perturbation Independent Decay of the Loschmidt Echo in a Many-Body System. PHYSICAL REVIEW LETTERS 2020; 124:030601. [PMID: 32031824 DOI: 10.1103/physrevlett.124.030601] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 07/05/2019] [Indexed: 06/10/2023]
Abstract
When a qubit or spin interacts with others under a many-body Hamiltonian, the information it contains progressively scrambles. Here, nuclear spins of an adamantane crystal are used as a quantum simulator to monitor such dynamics through out-of-time-order correlators, while a Loschmidt echo (LE) asses how weak perturbations degrade the information encoded in these increasingly complex states. Both observables involve the implementation of a time-reversal procedure which, in practice, involves inverting the sign of the effective Hamiltonian. Our protocols use periodic radio frequency pulses to modulate the natural dipolar interaction implementing a Hamiltonian that can be scaled down at will. Meanwhile, experimental errors and strength of perturbative terms remain constant and can be quantified through the LE. For each scaling factor, information spreading occurs with a timescale, T_{2}, inversely proportional to the local second moment of the Hamiltonian. We find that, when the reversible interactions dominate over the perturbations, the information scrambled among up to 10^{2} spins can still be recovered. However, we find that the LE decay rate cannot become smaller than a critical value 1/T_{3}≈(0.15±0.02)/T_{2}, which only depends on the interactions themselves, and not on the perturbations. This result shows the emergence of a regime of intrinsic irreversibility in accordance to a central hypothesis of irreversibility, hinted from previous experiments.
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Affiliation(s)
- C M Sánchez
- Facultad de Matemática, Astronomía, Física y Computación-Universidad Nacional de Córdoba, Córdoba X5000HUA, Argentina
| | - A K Chattah
- Facultad de Matemática, Astronomía, Física y Computación-Universidad Nacional de Córdoba, Córdoba X5000HUA, Argentina
- Instituto de Física Enrique Gaviola (CONICET-UNC), Córdoba X5000HUA, Argentina
| | - K X Wei
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - L Buljubasich
- Facultad de Matemática, Astronomía, Física y Computación-Universidad Nacional de Córdoba, Córdoba X5000HUA, Argentina
- Instituto de Física Enrique Gaviola (CONICET-UNC), Córdoba X5000HUA, Argentina
| | - P Cappellaro
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Nuclear Science & Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - H M Pastawski
- Facultad de Matemática, Astronomía, Física y Computación-Universidad Nacional de Córdoba, Córdoba X5000HUA, Argentina
- Instituto de Física Enrique Gaviola (CONICET-UNC), Córdoba X5000HUA, Argentina
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4
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Torres-Herrera EJ, Santos LF. Dynamical manifestations of quantum chaos: correlation hole and bulge. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2017; 375:rsta.2016.0434. [PMID: 29084885 PMCID: PMC5665786 DOI: 10.1098/rsta.2016.0434] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/22/2017] [Indexed: 06/07/2023]
Abstract
A main feature of a chaotic quantum system is a rigid spectrum where the levels do not cross. We discuss how the presence of level repulsion in lattice many-body quantum systems can be detected from the analysis of their time evolution instead of their energy spectra. This approach is advantageous to experiments that deal with dynamics, but have limited or no direct access to spectroscopy. Dynamical manifestations of avoided crossings occur at long times. They correspond to a drop, referred to as correlation hole, below the asymptotic value of the survival probability and to a bulge above the saturation point of the von Neumann entanglement entropy and the Shannon information entropy. By contrast, the evolution of these quantities at shorter times reflects the level of delocalization of the initial state, but not necessarily a rigid spectrum. The correlation hole is a general indicator of the integrable-chaos transition in disordered and clean models and as such can be used to detect the transition to the many-body localized phase in disordered interacting systems.This article is part of the themed issue 'Breakdown of ergodicity in quantum systems: from solids to synthetic matter'.
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Affiliation(s)
- E J Torres-Herrera
- Instituto de Física, Benemérita Universidad Autónoma de Puebla, Apt. Postal J-48, Puebla 72570, Mexico
| | - Lea F Santos
- Department of Physics, Yeshiva University, New York, NY 10016, USA
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Giusteri GG, Recrosi F, Schaller G, Celardo GL. Interplay of different environments in open quantum systems: Breakdown of the additive approximation. Phys Rev E 2017; 96:012113. [PMID: 29347125 DOI: 10.1103/physreve.96.012113] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Indexed: 11/07/2022]
Abstract
We analyze an open quantum system under the influence of more than one environment: a dephasing bath and a probability-absorbing bath that represents a decay channel, as encountered in many models of quantum networks. In our case, dephasing is modeled by random fluctuations of the site energies, while the absorbing bath is modeled with an external lead attached to the system. We analyze under which conditions the effects of the two baths can enter additively the quantum master equation. When such additivity is legitimate, the reduced master equation corresponds to the evolution generated by an effective non-Hermitian Hamiltonian and a Haken-Strobl dephasing super-operator. We find that the additive decomposition is a good approximation when the strength of dephasing is small compared to the bandwidth of the probability-absorbing bath.
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Affiliation(s)
- Giulio G Giusteri
- Mathematical Soft Matter Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, 904-0495, Okinawa, Japan.,Dipartimento di Matematica e Fisica and Interdisciplinary Laboratories for Advanced Materials Physics, Università Cattolica del Sacro Cuore, via Musei 41, I-25121 Brescia, Italy.,Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, via Bassi 6, I-27100, Pavia, Italy
| | - Filippo Recrosi
- Gran Sasso Science Institute, Viale Francesco Crispi 7, I-67100, L'Aquila, Italy
| | - Gernot Schaller
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstraße 36, D-10623 Berlin, Germany
| | - G Luca Celardo
- Dipartimento di Matematica e Fisica and Interdisciplinary Laboratories for Advanced Materials Physics, Università Cattolica del Sacro Cuore, via Musei 41, I-25121 Brescia, Italy.,Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, via Bassi 6, I-27100, Pavia, Italy.,Benemérita Universidad Autónoma de Puebla, Instituto de Física, Apartado Postal J-48, Puebla 72570, Mexico
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6
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Realistic Many-Body Quantum Systems vs. Full Random Matrices: Static and Dynamical Properties. ENTROPY 2016. [DOI: 10.3390/e18100359] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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7
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Sánchez CM, Levstein PR, Buljubasich L, Pastawski HM, Chattah AK. Quantum dynamics of excitations and decoherence in many-spin systems detected with Loschmidt echoes: its relation to their spreading through the Hilbert space. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2015.0155. [PMID: 27140972 PMCID: PMC4855398 DOI: 10.1098/rsta.2015.0155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/23/2016] [Indexed: 05/25/2023]
Abstract
In this work, we overview time-reversal nuclear magnetic resonance (NMR) experiments in many-spin systems evolving under the dipolar Hamiltonian. The Loschmidt echo (LE) in NMR is the signal of excitations which, after evolving with a forward Hamiltonian, is recovered by means of a backward evolution. The presence of non-diagonal terms in the non-equilibrium density matrix of the many-body state is directly monitored experimentally by encoding the multiple quantum coherences. This enables a spin counting procedure, giving information on the spreading of an excitation through the Hilbert space and the formation of clusters of correlated spins. Two samples representing different spin systems with coupled networks were used in the experiments. Protons in polycrystalline ferrocene correspond to an 'infinite' network. By contrast, the liquid crystal N-(4-methoxybenzylidene)-4-butylaniline in the nematic mesophase represents a finite proton system with a hierarchical set of couplings. A close connection was established between the LE decay and the spin counting measurements, confirming the hypothesis that the complexity of the system is driven by the coherent dynamics.
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Affiliation(s)
- C M Sánchez
- Facultad de Matemática Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba 5000, Argentina
| | - P R Levstein
- Facultad de Matemática Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba 5000, Argentina Instituto de Física Enrique Gaviola (IFEG-CONICET), Ciudad Universitaria, Córdoba 5000, Argentina
| | - L Buljubasich
- Facultad de Matemática Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba 5000, Argentina Instituto de Física Enrique Gaviola (IFEG-CONICET), Ciudad Universitaria, Córdoba 5000, Argentina
| | - H M Pastawski
- Facultad de Matemática Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba 5000, Argentina Instituto de Física Enrique Gaviola (IFEG-CONICET), Ciudad Universitaria, Córdoba 5000, Argentina
| | - A K Chattah
- Facultad de Matemática Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba 5000, Argentina Instituto de Física Enrique Gaviola (IFEG-CONICET), Ciudad Universitaria, Córdoba 5000, Argentina
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8
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Goussev A, Jalabert RA, Pastawski HM, Wisniacki DA. Loschmidt echo and time reversal in complex systems. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2015.0383. [PMID: 27140977 PMCID: PMC4855404 DOI: 10.1098/rsta.2015.0383] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 03/10/2016] [Indexed: 06/05/2023]
Abstract
Echoes are ubiquitous phenomena in several branches of physics, ranging from acoustics, optics, condensed matter and cold atoms to geophysics. They are at the base of a number of very useful experimental techniques, such as nuclear magnetic resonance, photon echo and time-reversal mirrors. Particularly interesting physical effects are obtained when the echo studies are performed on complex systems, either classically chaotic, disordered or many-body. Consequently, the term Loschmidt echo has been coined to designate and quantify the revival occurring when an imperfect time-reversal procedure is applied to a complex quantum system, or equivalently to characterize the stability of quantum evolution in the presence of perturbations. Here, we present the articles which discuss the work that has shaped the field in the past few years.
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Affiliation(s)
- Arseni Goussev
- Department of Mathematics and Information Sciences, Northumbria University, Newcastle Upon Tyne NE1 8ST, UK
| | - Rodolfo A Jalabert
- Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504, Strasbourg 67034, France
| | - Horacio M Pastawski
- Instituto de Física Enrique Gaviola (CONICET-UNC) and Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Córdoba 5000, Argentina
| | - Diego A Wisniacki
- Departamento de Física and IFIBA, FCEyN, UBA Ciudad Universitaria, Pabellón 1, Ciudad Universitaria, Buenos Aires 1428, Argentina
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Buljubasich L, Sánchez CM, Dente AD, Levstein PR, Chattah AK, Pastawski HM. Experimental quantification of decoherence via the Loschmidt echo in a many spin system with scaled dipolar Hamiltonians. J Chem Phys 2015; 143:164308. [PMID: 26520514 DOI: 10.1063/1.4934221] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We performed Loschmidt echo nuclear magnetic resonance experiments to study decoherence under a scaled dipolar Hamiltonian by means of a symmetrical time-reversal pulse sequence denominated Proportionally Refocused Loschmidt (PRL) echo. The many-spin system represented by the protons in polycrystalline adamantane evolves through two steps of evolution characterized by the secular part of the dipolar Hamiltonian, scaled down with a factor |k| and opposite signs. The scaling factor can be varied continuously from 0 to 1/2, giving access to a range of complexity in the dynamics. The experimental results for the Loschmidt echoes showed a spreading of the decay rates that correlate directly to the scaling factors |k|, giving evidence that the decoherence is partially governed by the coherent dynamics. The average Hamiltonian theory was applied to give an insight into the spin dynamics during the pulse sequence. The calculations were performed for every single radio frequency block in contrast to the most widely used form. The first order of the average Hamiltonian numerically computed for an 8-spin system showed decay rates that progressively decrease as the secular dipolar Hamiltonian becomes weaker. Notably, the first order Hamiltonian term neglected by conventional calculations yielded an explanation for the ordering of the experimental decoherence rates. However, there is a strong overall decoherence observed in the experiments which is not reflected by the theoretical results. The fact that the non-inverted terms do not account for this effect is a challenging topic. A number of experiments to further explore the relation of the complete Hamiltonian with this dominant decoherence rate are proposed.
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Affiliation(s)
| | - Claudia M Sánchez
- Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba 5000, Argentina
| | - Axel D Dente
- Instituto de Física Enrique Gaviola (IFEG-CONICET), Córdoba 5000, Argentina
| | | | - Ana K Chattah
- Instituto de Física Enrique Gaviola (IFEG-CONICET), Córdoba 5000, Argentina
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Ruderman A, Dente AD, Santos E, Pastawski HM. Molecular dissociation in the presence of catalysts: interpreting bond breaking as a quantum dynamical phase transition. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:315501. [PMID: 26189372 DOI: 10.1088/0953-8984/27/31/315501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In this work we show that molecular chemical bond formation and dissociation in the presence of the d-band of a metal catalyst can be described as a quantum dynamical phase transition (QDPT). This agrees with DFT calculations that predict sudden jumps in some observables as the molecule breaks. According to our model this phenomenon emerges because the catalyst provides for a non-Hermitian Hamiltonian. We show that when the molecule approaches the surface, as occurs in the Heyrovsky reaction of H2, the bonding H2 orbital has a smooth crossover into a bonding molecular orbital built with the closest H orbital and the surface metal d-states. The same occurs for the antibonding state. Meanwhile, two resonances appear within the continuous spectrum of the d-band, which are associated with bonding and antibonding orbitals between the furthest H atom and the d-states at the second metallic layer. These move toward the band center, where they collapse into a pure metallic resonance and an almost isolated H orbital. This phenomenon constitutes a striking example of the non-trivial physics enabled when one deals with non-Hermitian Hamiltonian beyond the usual wide band approximation.
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Affiliation(s)
- A Ruderman
- Instituto de Física Enrique Gaviola (CONICET), Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina. Institute of Theoretical Chemistry, Ulm University, D-89069 Ulm, Germany
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11
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Cattena CJ, Fernández-Alcázar LJ, Bustos-Marún RA, Nozaki D, Pastawski HM. Generalized multi-terminal decoherent transport: recursive algorithms and applications to SASER and giant magnetoresistance. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:345304. [PMID: 25105444 DOI: 10.1088/0953-8984/26/34/345304] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Decoherent transport in mesoscopic and nanoscopic systems can be formulated in terms of the D'Amato-Pastawski (DP) model. This generalizes the Landauer-Büttiker picture by considering a distribution of local decoherent processes. However, its generalization for multi-terminal set-ups is lacking. We first review the original two-terminal DP model for decoherent transport. Then, we extend it to a matrix formulation capable of dealing with multi-terminal problems. We also introduce recursive algorithms to evaluate the Green's functions for general banded Hamiltonians as well as local density of states, effective conductances and voltage profiles. We finally illustrate the method by analyzing two problems of current relevance. (1) Assessing the role of decoherence in a model for phonon lasers (SASER). (2) Obtaining the classical limit of giant magnetoresistance from a spin-dependent Hamiltonian. The presented methods should pave the way for computationally demanding calculations of transport through nanodevices, bridging the gap between fully coherent quantum schemes and semiclassical ones.
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Affiliation(s)
- Carlos J Cattena
- Instituto de Física Enrique Gaviola and Facultad de Matemática Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba 5000, Argentina
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12
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Álvarez GA, Shemesh N, Frydman L. Coherent dynamical recoupling of diffusion-driven decoherence in magnetic resonance. PHYSICAL REVIEW LETTERS 2013; 111:080404. [PMID: 24010418 DOI: 10.1103/physrevlett.111.080404] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Indexed: 06/02/2023]
Abstract
During recent years, dynamical decoupling (DD) has gained relevance as a tool for manipulating and interrogating quantum systems. This is particularly relevant for spins involved in nuclear magnetic resonance (NMR), where DD sequences can be used to prolong quantum coherences, or to selectively couple or decouple the effects imposed by random environmental fluctuations. In this Letter, we show that these concepts can be exploited to selectively recouple diffusion processes in restricted spaces. The ensuing method provides a novel tool to measure restriction lengths in confined systems such as capillaries, pores or cells. The principles of this method for selectively recoupling diffusion-driven decoherence, its standing within the context of diffusion NMR, extensions to the characterization of other kinds of quantum fluctuations, and corroborating experiments, are presented.
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Affiliation(s)
- Gonzalo A Álvarez
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel
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13
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Bullo DE, Wisniacki DA. Perturbations and chaos in quantum maps. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:026206. [PMID: 23005844 DOI: 10.1103/physreve.86.026206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Indexed: 06/01/2023]
Abstract
The local density of states (LDOS) is a distribution that characterizes the effects of perturbations on quantum systems. Recently, a semiclassical theory was proposed for the LDOS of chaotic billiards and maps. This theory predicts that the LDOS is a Breit-Wigner distribution independent of the perturbation strength and also gives a semiclassical expression for the LDOS width. Here, we test the validity of such an approximation in quantum maps by varying the degree of chaoticity, the region in phase space where the perturbation is applied, and the intensity of the perturbation. We show that for highly chaotic maps or strong perturbations the semiclassical theory of the LDOS is accurate to describe the quantum distribution. Moreover, the width of the LDOS is also well represented for its semiclassical expression in the case of mixed classical dynamics.
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Affiliation(s)
- Darío E Bullo
- Departamento de Física J J Giambiagi, FCEN, Universidad de Buenos Aires, 1428 Buenos Aires, Argentina
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14
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Cappellaro P, Ramanathan C, Cory DG. Simulations of information transport in spin chains. PHYSICAL REVIEW LETTERS 2007; 99:250506. [PMID: 18233510 DOI: 10.1103/physrevlett.99.250506] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2007] [Indexed: 05/25/2023]
Abstract
Transport of quantum information in linear spin chains has been the subject of much theoretical work. Experimental studies by NMR in solid state spin systems (a natural implementation of such models) is complicated since the dipolar Hamiltonian is not solely comprised of nearest-neighbor XY-Heisenberg couplings. We present here a similarity transformation between the XY Hamiltonian and the double-quantum Hamiltonian, an interaction which is achievable with the collective control provided by radio-frequency pulses. Not only can this second Hamiltonian simulate the information transport in a spin chain, but it also creates coherent states, whose intensities give an experimental signature of the transport. This scheme makes it possible to study experimentally the transport of polarization beyond exactly solvable models and explore the appearance of quantum coherence and interference effects.
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Affiliation(s)
- P Cappellaro
- ITAMP-Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA
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