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Swain A, Sharma T, Rajaraman G. Strategies to quench quantum tunneling of magnetization in lanthanide single molecule magnets. Chem Commun (Camb) 2023; 59:3206-3228. [PMID: 36789911 DOI: 10.1039/d2cc06041h] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Enhancing blocking temperature (TB) is one of the holy grails in Single Molecule Magnets(SMMs), as any future potential application in this class of molecules is directly correlated to this parameter. Among many factors contributing to a reduction of TB value, Quantum Tunnelling of Magnetisation (QTM), a phenomenon that is a curse or a blessing based on the application sought after, tops the list. Theoretical tools based on density functional and ab initio CASSCF/RASSI-SO methods have played a prominent role in estimating various spin Hamiltonian parameters and establishing the mechanism of magnetization relaxation in this class of molecules. Particularly, various strategies to quench QTM effects go hand-in-hand with experiments, and different methods proposed to quell QTM effects are scattered in the literature. In this perspective, we have explored various approaches that are proposed in the literature to quench QTM effects, and these include the role of (i) local symmetry of lanthanides, (ii) super-exchange interaction in {3d-4f} complexes, (iii) direct-exchange interaction in {radical-4f} and metal-metal bonded complexes to suppress the QTM, (iv) utilizing external stimuli such as an electric field or pressure to modulate the QTM and (v) avoiding QTM effects by stabilising toroidal states in 4f and {3d-4f} clusters. We believe the strategies summarized here will help to design new-generation SMMs.
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Affiliation(s)
- Abinash Swain
- Department of Chemistry, IIT Bombay, Powai, Mumbai - 400076, India.
| | - Tanu Sharma
- Department of Chemistry, IIT Bombay, Powai, Mumbai - 400076, India.
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Magazzù L, Denisov S, Hänggi P. Asymptotic Floquet states of a periodically driven spin-boson system in the nonperturbative coupling regime. Phys Rev E 2018; 98:022111. [PMID: 30253481 DOI: 10.1103/physreve.98.022111] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Indexed: 06/08/2023]
Abstract
Being an exemplary model of open quantum system, the spin-boson model is widely employed in theoretical and experimental studies. Beyond the weak coupling limit, the spin-boson dynamics can be described by a time-nonlocal generalized master equation with a memory kernel accounting for the dissipative effects induced by the bosonic environment. When the spin is in addition modulated by an external time-periodic electromagnetic field, the interplay between dissipation and forcing provides a spectrum of nontrivial asymptotic states, especially so in the regime of nonlinear response. Here we implement the method for evaluating the dissipative Floquet dynamics of non-Markovian systems introduced in Magazzù et al. [Phys. Rev. A 96, 042103 (2017)2469-992610.1103/PhysRevA.96.042103] to obtain these nonequilibrium asymptotic states.
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Affiliation(s)
- Luca Magazzù
- Institute of Physics, University of Augsburg, Universitätsstrasse 1, D-86135 Augsburg, Germany
| | - Sergey Denisov
- Institute of Physics, University of Augsburg, Universitätsstrasse 1, D-86135 Augsburg, Germany
- Department of Applied Mathematics, Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod 603950, Russia
- Sumy State University, Rimsky-Korsakov Street 2, 40007 Sumy, Ukraine
| | - Peter Hänggi
- Institute of Physics, University of Augsburg, Universitätsstrasse 1, D-86135 Augsburg, Germany
- Nanosystems Initiative Munich, Schellingstraße 4, D-80799 München, Germany
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Enhancing Metastability by Dissipation and Driving in an Asymmetric Bistable Quantum System. ENTROPY 2018; 20:e20040226. [PMID: 33265317 PMCID: PMC7512741 DOI: 10.3390/e20040226] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 03/01/2018] [Accepted: 03/23/2018] [Indexed: 12/19/2022]
Abstract
The stabilizing effect of quantum fluctuations on the escape process and the relaxation dynamics from a quantum metastable state are investigated. Specifically, the quantum dynamics of a multilevel bistable system coupled to a bosonic Ohmic thermal bath in strong dissipation regime is analyzed. The study is performed by a non-perturbative method based on the real-time path integral approach of the Feynman-Vernon influence functional. We consider a strongly asymmetric double well potential with and without a monochromatic external driving, and with an out-of-equilibrium initial condition. In the absence of driving we observe a nonmonotonic behavior of the escape time from the metastable region, as a function both of the system-bath coupling coefficient and the temperature. This indicates a stabilizing effect of the quantum fluctuations. In the presence of driving our findings indicate that, as the coupling coefficient γ increases, the escape time, initially controlled by the external driving, shows resonant peaks and dips, becoming frequency-independent for higher γ values. Moreover, the escape time from the metastable state displays a nonmonotonic behavior as a function of the temperature, the frequency of the driving, and the thermal-bath coupling, which indicates the presence of a quantum noise enhanced stability phenomenon. Finally, we investigate the role of different spectral densities, both in sub-Ohmic and super-Ohmic dissipation regime and for different cutoff frequencies, on the relaxation dynamics from the quantum metastable state. The results obtained indicate that, in the crossover dynamical regime characterized by damped intrawell oscillations and incoherent tunneling, the spectral properties of the thermal bath influence non-trivially the short time behavior and the time scales of the relaxation dynamics from the metastable state.
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Magazzù L, Valenti D, Spagnolo B, Grifoni M. Dissipative dynamics in a quantum bistable system: crossover from weak to strong damping. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:032123. [PMID: 26465442 DOI: 10.1103/physreve.92.032123] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Indexed: 06/05/2023]
Abstract
The dissipative dynamics of a quantum bistable system coupled to a Ohmic heat bath is investigated beyond the spin-boson approximation. Within the path-integral approach to quantum dissipation, we propose an approximation scheme which exploits the separation of time scales between intra- and interwell (tunneling) dynamics. The resulting generalized master equation for the populations in a space localized basis enables us to investigate a wide range of temperatures and system-environment coupling strengths. A phase diagram in the coupling-temperature space is provided to give a comprehensive account of the different dynamical regimes.
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Affiliation(s)
- Luca Magazzù
- Dipartimento di Fisica e Chimica, Università di Palermo, Viale delle Scienze, Edificio 18, I-90128 Palermo, Italy
- Radiophysics Department, Lobachevsky State University of Nizhni Novgorod, Russia
| | - Davide Valenti
- Dipartimento di Fisica e Chimica, Università di Palermo, Viale delle Scienze, Edificio 18, I-90128 Palermo, Italy
| | - Bernardo Spagnolo
- Dipartimento di Fisica e Chimica, Università di Palermo, Viale delle Scienze, Edificio 18, I-90128 Palermo, Italy
- Radiophysics Department, Lobachevsky State University of Nizhni Novgorod, Russia
- Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Italy
| | - Milena Grifoni
- Theoretische Physik, Universität Regensburg, 93040 Regensburg, Germany
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Multi-State Quantum Dissipative Dynamics in Sub-Ohmic Environment: The Strong Coupling Regime. ENTROPY 2015. [DOI: 10.3390/e17042341] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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7
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Pomyalov A, Meier C, Tannor D. The importance of initial correlations in rate dynamics: A consistent non-Markovian master equation approach. Chem Phys 2010. [DOI: 10.1016/j.chemphys.2010.02.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Nest M, Kosloff R. Quantum dynamical treatment of inelastic scattering of atoms at a surface at finite temperature: the random phase thermal wave function approach. J Chem Phys 2007; 127:134711. [PMID: 17919047 DOI: 10.1063/1.2786088] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
We present quantum dynamical calculations for the inelastic scattering of atoms at a nonrigid surface at finite temperature. The surface degrees of freedom are discretized and treated in a multiconfigurational wave function picture. The thermal averaging is carried out with the random phase thermal wave function approach. We show that it is sufficient to restrict the random phases to the intermediate basis of single particle functions, discuss the convergence of the method with the number of configurations and realizations, and analyze the flow of energy between different parts of the system for a range of temperatures between 4 and 500 K.
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Affiliation(s)
- M Nest
- Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Str. 25, 14476 Potsdam, Germany.
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Wernsdorfer W. Classical and Quantum Magnetization Reversal Studied in Nanometer-Sized Particles and Clusters. ADVANCES IN CHEMICAL PHYSICS 2007. [DOI: 10.1002/9780470141786.ch3] [Citation(s) in RCA: 199] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Peano V, Thorwart M. Dynamics of the quantum Duffing oscillator in the driving induced bistable regime. Chem Phys 2006. [DOI: 10.1016/j.chemphys.2005.06.047] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Real-time Monte-Carlo simulations for dissipative tight-binding systems and time local master equations. Chem Phys 2006. [DOI: 10.1016/j.chemphys.2005.07.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Lehmann J, Kohler S, May V, Hänggi P. Vibrational effects in laser-driven molecular wires. J Chem Phys 2004; 121:2278-88. [PMID: 15260783 DOI: 10.1063/1.1768154] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The influence of an electron-vibrational coupling on the laser control of electron transport through a molecular wire that is attached to several electronic leads is investigated. These molecular vibrational modes induce an effective electron-electron interaction. In the regime where the wire electrons couple weakly to both the external leads and the vibrational modes, we derive within a Hartree-Fock approximation a nonlinear set of quantum kinetic equations. The quantum kinetic theory is then used to evaluate the laser driven, time-averaged electron current through the wire-leads contacts. This formalism is applied to two archetypical situations in the presence of electron-vibrational effects, namely, (i) the generation of a ratchet or pump current in a symmetrical molecule by a harmonic mixing field and (ii) the laser switching of the current through the molecule.
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Affiliation(s)
- Jörg Lehmann
- Institut für Physik, Universität Augsburg, Universitätsstrasse 1, D-86135, Germany
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Petrov E, May V, Hänggi P. Spin-boson description of electron transmission through a molecular wire. Chem Phys 2004. [DOI: 10.1016/j.chemphys.2003.09.021] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Dynamics of Dissipative Quantum Systems: From Path Integrals to Master Equations. ACTA ACUST UNITED AC 2003. [DOI: 10.1007/3-540-44874-8_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Majer JB, Peguiron J, Grifoni M, Tusveld M, Mooij JE. Quantum ratchet effect for vortices. PHYSICAL REVIEW LETTERS 2003; 90:056802. [PMID: 12633384 DOI: 10.1103/physrevlett.90.056802] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2002] [Indexed: 05/24/2023]
Abstract
We have measured a quantum ratchet effect for vortices moving in a quasi-one-dimensional Josephson junction array. In this solid-state device the shape of the vortex potential energy, and consequently the band structure, can be accurately designed. This band structure determines the presence or absence of the quantum ratchet effect. In particular, asymmetric structures possessing only one band below the barrier do not exhibit current rectification at low temperatures and bias currents. The quantum nature of transport is also revealed in a universal/nonuniversal power-law dependence of the measured voltage-current characteristics for samples without/with rectification.
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Affiliation(s)
- J B Majer
- Department of Nanoscience, Delft University of Technology, Lorentzweg 1, The Netherlands
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Grifoni M, Ferreira MS, Peguiron J, Majer JB. Quantum ratchets with few bands below the barrier. PHYSICAL REVIEW LETTERS 2002; 89:146801. [PMID: 12366063 DOI: 10.1103/physrevlett.89.146801] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2002] [Indexed: 05/23/2023]
Abstract
We investigate directed motion in nonadiabatically rocked ratchet systems sustaining few bands below the barrier. Upon restricting the dynamics to the lowest M bands, the total system-plus-bath Hamiltonian is mapped onto a discrete tight-binding model containing all the information both on the intrawell and interwell tunneling motion. A closed form for the current in the incoherent tunneling regime is obtained. In effective single-band ratchets, no current rectification occurs. We apply our theory to describe rectification effects in vortex quantum ratchets devices. Current reversals upon variation of the ac-field amplitude or frequency are predicted.
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Affiliation(s)
- M Grifoni
- Department of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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Ankerhold J. Quantum decay rates for driven barrier potentials in the strong friction limit. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001; 64:060102. [PMID: 11736160 DOI: 10.1103/physreve.64.060102] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2001] [Indexed: 05/23/2023]
Abstract
Quantum decay rates for barrier potentials driven by external stochastic and periodic forces in the strong damping regime are studied. Based on the quantum Smoluchowski equation derived recently by Ankerhold, Pechukas, and Grabert [Phys. Rev. Lett. 87, 086802 (2001)] explicit analytical and numerical results are presented for the case of the resonant activation phenomenon in a bistable potential and the escape from a metastable well with oscillating barrier, respectively. The significant impact of quantum fluctuations is revealed.
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Affiliation(s)
- J Ankerhold
- Fakultät für Physik, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Strasse 3, D-79104 Freiburg, Germany
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Casado-Pascual J, Denk C, Morillo M, Cukier R. Path-integral approach to a semiclassical stochastic description of quantum dissipative systems. Chem Phys 2001. [DOI: 10.1016/s0301-0104(01)00301-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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