Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 10 de 10
Filter
Add more filters










Publication year range
1.
J Phys Condens Matter ; 35(44)2023 Aug 08.
Article in English | MEDLINE | ID: mdl-37506708

ABSTRACT

Interfacing magnetism with superconducting condensates are promising candidates holding Majorana bound states with which fault-tolerant quantum computation could be implemented. Within this field, understanding the detailed dynamics is important both for fundamental reasons and for the development of innovative quantum technologies. Herein, motivated by a molecular magnet Tb2Pc3interacting with a superconducting Pb(111) substrate, which results in spin-orbital Yu-Shiba-Rusinov (YSR) states, as is affirmed by a theoretical simulation with the aid of the numerical renormalization group technique (see Xiaet al2022Nat. Commun.136388), we study the YSR states and quantum phase transitions (QPTs) in a bipartite molecular device adsorbed on ans-wave superconducting substrate. We highlight the effect of asymmetric Coulomb repulsion by computing the spectrum function and spin correlation function in various parameter regimes. We demonstrate that if one impurity is non-interacting, there are no YSR states in both impurities with any repulsion value in the other impurity. Whereas if the repulsion in one impurity is strong, the YSR states are observed in both impurities, and a QPT arises as the repulsion in the other impurity sweeps, assisted by the competition between the superconducting singlet (Cooper pair) and the Kondo singlet. The evolution of YSR states distinguishes from the single impurity case and can be well interpreted by the energy scales of the isotropic superconducting gap parameter, as well as the two Kondo temperatures. Our findings provide theoretical insights into the phase diagram of two magnetic impurities on a superconducting host and shine light on the effects induced by asymmetric Coulomb repulsion on many-body interactions.

2.
Phys Chem Chem Phys ; 24(37): 22546-22556, 2022 Sep 28.
Article in English | MEDLINE | ID: mdl-36106516

ABSTRACT

Regulating the physical properties such as the quantum phase and the Kondo effect of molecular electronic devices near critical points may play a key role in increasing the robustness of quantum memory, which is a crucial component in quantum information processing. Molecules with a triangular topology are ideal prototypes to reveal the competition among magnetic frustration, Kondo screening, and local inter-molecule exchange interactions. Herein, motivated by a recent work investigating the single-electron tunneling through a redox-active edge-fused porphyrin trimer by using a Hubbard dimer model [J. O. Thomas, J. K. Sowa, B. Limburg, X. Bian, C. Evangeli, J. L. Swett, S. Tewari, J. Baugh, G. C. Schatz, G. A. D. Briggs, H. L. Anderson and J. A. Mol, Chem. Sci., 2021, 12, 11121], we studied the phase transition, the electronic transport, and the thermodynamical properties of a real molecular trimer structure organized in a triangular topology, with and without an external magnetic field, and at zero and non-zero temperatures. Both the Hubbard electron-electron interaction and the Heisenberg exchange interaction are fully taken into account, with the aid of the state-of-the-art numerical renormalization group method. Various kinds of Kondo behaviors and quantum phase transitions are demonstrated, due to the competition among the Ruderman-Kittel-Kasuya-Yosida interaction, the direct exchange coupling, and the Zeeman effect. Our findings may offer deep insights into the manipulation of the quantum phase and the Kondo behavior in a molecular trimer with a triangular topology.

3.
J Chem Phys ; 157(10): 104118, 2022 Sep 14.
Article in English | MEDLINE | ID: mdl-36109223

ABSTRACT

We derive a rigorous nuclear gradient for a molecule-cavity hybrid system using the quantum electrodynamics Hamiltonian. We treat the electronic-photonic degrees of freedom (DOFs) as the quantum subsystem and the nuclei as the classical subsystem. Using the adiabatic basis for the electronic DOF and the Fock basis for the photonic DOF and requiring the total energy conservation of this mixed quantum-classical (MQC) system, we derived the rigorous nuclear gradient for the molecule-cavity hybrid system, which is naturally connected to the approximate gradient under the Jaynes-Cummings approximation. The nuclear gradient expression can be readily used in any MQC simulations and will allow one to perform the non-adiabatic on-the-fly simulation of polariton quantum dynamics. The theoretical developments in this work could significantly benefit the polariton quantum dynamics community with a rigorous nuclear gradient of the molecule-cavity hybrid system and have a broad impact on the future non-adiabatic simulations of polariton quantum dynamics.

4.
Phys Chem Chem Phys ; 24(34): 20040-20049, 2022 Aug 31.
Article in English | MEDLINE | ID: mdl-35833449

ABSTRACT

The precise manipulation of the quantum states of individual atoms/molecules adsorbed on metal surfaces is one of the most exciting frontiers in nanophysics, enabling us to realize novel single molecular logic devices and quantum information processing. Herein, by modeling an iron phthalocyanine molecule adsorbed on the Au(111) surface with a two-impurity Anderson model, we demonstrate that the quantum states of such a system could be adjusted by the uniaxial magnetic anisotropy Dz. For negative Dz, the ground state is dominated by a parallel configuration of the z component of local spins, whereas it turns to be an antiparallel one when Dz becomes positive. Interestingly, we found that these two phases are separated by a Kosterlitz-Thouless-type quantum phase transition, which is confirmed by the critical behaviors of the transmission coefficient and the local magnetic moment. Both phases are associated with spin correlation anisotropy, thus move against the Kondo effect. When the external magnetic field is applied, it first plays a role in compensating for the effect of Dz, and then it contributes significantly to the Zeeman effect for positive Dz, accompanied by the reappearance and the splitting of the Kondo peak, respectively. For fixed negative Dz, only the Zeeman behavior is revealed. Our results provide deep insights into the manipulation of the quantum phase within a single molecular junction.

5.
Phys Chem Chem Phys ; 24(9): 5522-5528, 2022 Mar 02.
Article in English | MEDLINE | ID: mdl-35171974

ABSTRACT

Interactions between quantum systems and their environments may always result in inevitable decoherence. Isolation of the quantum system from the undesired environmental noise is a great challenge for ideal quantum information processing. Herein, based on a parallelly shaped control-target molecular nanomagnet structure, we report a novel strategy which decouples the target molecular device from its surrounding conduction baths. By tuning the level differences between the control and target orbitals through external gate voltages, one manipulates both, neither or only the target subsystem to contribute to the quantum transport in sequence, corresponding to an "on-off-on" behavior in the linear conductance. In the off window, a local transport circulation develops, preventing the target device from being disturbed by the itinerant electrons. This finding provides a prospective method for confining integrated quantum devices with high intrinsic fidelity, remarkable tunability, and universal suitability.

6.
Phys Rev Lett ; 125(12): 123602, 2020 Sep 18.
Article in English | MEDLINE | ID: mdl-33016745

ABSTRACT

This work provides the fundamental theoretical framework for molecular cavity quantum electrodynamics by resolving the gauge ambiguities between the Coulomb gauge and the dipole gauge Hamiltonians under the electronic state truncation. We conjecture that such ambiguity arises because not all operators are consistently constrained in the same truncated electronic subspace for both gauges. We resolve this ambiguity by constructing a unitary transformation operator that properly constrains all light-matter interaction terms in the same subspace. We further derive an equivalent and yet convenient expression for the Coulomb gauge Hamiltonian under the truncated subspace. We finally provide the analytical and numerical results of a model molecular system coupled to the cavity to demonstrate the validity of our theory.

7.
Phys Chem Chem Phys ; 22(2): 422-429, 2020 Jan 02.
Article in English | MEDLINE | ID: mdl-31793961

ABSTRACT

The use of the molecular spin state as a quantum of next-generation information technology is receiving impressive research attention, within which the fundamental issues include manipulating the phase transition between the spin-up and -down states and generating spin polarized current. The spinterface between ferromagnetic electrodes and a molecular bridge represents one of the most intriguing elements in this context. Herein, by means of the celebrated numerical renormalization group technique, we present an original way to realize spin reversal in a monomeric dimer. Our scheme is based on the exchange interactions between electronic spins on one monomer and those on the other one or on the electrodes, which could be easily controlled through purely electronic technology. Through a careful engineering of the interfacial parameters, one of the monomers is devoted to the spin reversing, whereas the other one contributes to the spin selecting. The charge numbers of spin-up and -down electrons swap their respective occupancies at some particular points, indicating charge sensing between different spins. The competition between the spinterface and the molecular energy level results in charge oscillating in a single spin channel, which is unfavorable to the spin selecting. The observation may provide a prospective example for a multifunctional magnetoelectronics molecular device, which works without any external magnetic field.

8.
J Phys Chem Lett ; 10(22): 7062-7070, 2019 Nov 21.
Article in English | MEDLINE | ID: mdl-31665889

ABSTRACT

We use the quasi-diabatic (QD) propagation scheme to perform on-the-fly nonadiabatic simulations of the photodynamics of ethylene. The QD scheme enables a seamless interface between accurate diabatic-based quantum dynamics approaches and adiabatic electronic structure calculations, explicitly avoiding any efforts to construct global diabatic states or reformulate the diabatic dynamics approach to the adiabatic representation. Using the partial linearized path-integral approach and the symmetrical quasi-classical approach as the diabatic dynamics methods, the QD propagation scheme enables direct nonadiabatic simulation with complete active space self-consistent field on-the-fly electronic structure calculations. The population dynamics obtained from both approaches are in a close agreement with the quantum wavepacket-based method and outperform the widely used trajectory surface-hopping approach. Further analysis of the ethylene photodeactivation pathways demonstrates the correct predictions of competing processes of nonradiative relaxation mechanism through various conical intersections. This work provides the foundation of using accurate diabatic dynamics approaches and on-the-fly adiabatic electronic structure information to perform ab initio nonadiabatic simulation.

9.
Phys Chem Chem Phys ; 21(39): 21693-21697, 2019 Oct 09.
Article in English | MEDLINE | ID: mdl-31556898

ABSTRACT

Molecular spintronics devices are receiving extensive research attention, due to their potential applications as the smallest memory and logic elements. A most fundamental issue in this field lies in generating spin polarized currents. In this communication, with the aid of the celebrated Wilson's numerical renormalization group (NRG) method, we propose theoretically a novel strategy to induce a local magnetic field that only affects the strongly correlated molecule under consideration, and could easily be manipulated through purely electronic technologies. It is also demonstrated that the device may lead to bidirectional spin polarization, where perfectly polarized spin-up and -down currents could be obtained by simply adjusting the energy level of the molecule to different regions along a single direction. Our suggested model is based on a molecular break-junction with a magnetic radical. It may provide a prospective example of a magnetoelectronics device at the molecular scale, which works without an external magnetic field.

10.
J Chem Phys ; 150(6): 064110, 2019 Feb 14.
Article in English | MEDLINE | ID: mdl-30770009

ABSTRACT

Metal-molecule-metal junction is considered the basing block and key element of molecular spintronic devices, within which to generate spin polarized currents is one of the most fundamental issues for quantum computation and quantum information. In this paper, by employing a parallel triple orbital molecule junction with large inter-orbital tunneling couplings, we propose theoretically a bidirectional spin filter where both spin-up and spin-down currents could be obtained by simply adjusting the external magnetic field to different regimes along a single direction, and the filtered efficiencies could reach almost 100%. The Zeeman effect and the occupancy switching for the bonding and anti-bonding states are found to be responsible for the spin selective transport. We demonstrate that our scheme is robust for large parameter spaces of the orbital energy level, except the particle-hole symmetric point, and is widely suitable for the strong-, weak-, and non-interacting cases. To implement these problems, we use the Wilson's numerical renormalization group technique to treat such systems.

SELECTION OF CITATIONS
SEARCH DETAIL
...