Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session B58: Single Molecule Magnets IFocus
|
Hide Abstracts |
Sponsoring Units: GMAG Chair: Xianglin Ke, Michigan State University Room: Room 302 |
Monday, March 6, 2023 11:30AM - 12:06PM |
B58.00001: Probing Molecular Magnetism and a Haldane MOF by Advanced Spectroscopies Invited Speaker: Ziling (Ben) Xue This talk will focus on our recent studies of single-molecule magnets (SMMs) and a 2D Haldane MOF (metal-organic framework) by far-IR and Raman magneto-spectroscopies (FIRMS and RaMS), inelastic neutron scattering (INS), and high-field EPR (HFEPR). SMMs are of intense interest as a new generation of data storage and spintronics materials. Haldane topological materials in the form of MOFs possess an unusual structure. For SMMs, zero-field splittings (ZFS) in d-metal complexes and intra-manifold separations in f-metal complexes lead to barriers for their magnetic relaxations. We have successfully used the spectroscopies to determine large separations in several SMMs, including CoI2(AsPh3)2 [1], Co(acac-d7)2(D2O)2 (acac = acetylacetonate) [2], Co(14-crown-4)22+ [3], and Er[N(SiMe3)2]3 [4]. In addition, the spectroscopies reveal rarely observed spin-phonon couplings in the molecular compounds. For the topological material, we have found that a 2D Ni(II) MOF possesses a Haldane gap. Our studies of SMMs and the MOF will be presented. |
Monday, March 6, 2023 12:06PM - 12:18PM |
B58.00002: Critical slowing-down of phonon dynamics in a cobalt(II) single-molecule magnet Yinchuan Lv, Yidi Liu, Nicole A Bone, Ziling (Ben) Xue, Fahad Mahmood Single-molecule magnets (SMMs) are promising candidates for molecule-scale spin qubits and high-density information storage. The lattice vibration inside SMMs can modulate the crystal electric field of the central metal ions, allowing direct transitions between different spin states. Such spin-phonon coupling is a major source of decoherence or unwanted magnetic relaxation, yet can be tailored for spin manipulation. The coupling is thus of central importance for SMMs’ spintronics applications. Here, we investigate the critical behavior of magnetic relaxation inside an eight-coordinate, molecule-magnet complex, cobalt(II)-12-crown-4, through terahertz (THz) time-domain spectroscopy (TDTS) and THz electron paramagnetic resonance (EPR). The temperature-dependent study shows a prominent critical slowing-down of a 0.8 THz phonon oscillation lifetime across the Curie point, indicating strong spin-phonon coupling for this phonon mode. The same critical behavior is not shown in other absorption peaks, e.g., at 0.5 THz. Our study pinpoints the energy scale of spin-phonon coupling in this system, laying the groundwork for ultrafast switching of spin states inside single-molecule magnets. |
Monday, March 6, 2023 12:18PM - 12:30PM |
B58.00003: First Principle Resonant Raman Intensity Calculations of Single-Molecule Magnet Dimers ([Mn3]2) Xiaoguang Zhang, Guanzhi Li, Hai-Ping Cheng, Rui Zhang, Yue Yu, Tao Jiang, Duy Le, Talat S Rahman Resonant Raman spectra of a molecule at different spin quantum state have different enhancement, making it possible to identify spin quantum state of single-molecule magnets (SMMs). By using Density Functional Theory, we calculate optimized structures of AFM and FM Single-Molecule Magnet Dimers ([Mn3]2) in electronic ground state and excited states. We apply first principle resonant Raman scattering theory and calculate resonant Raman spectra of [Mn3]2 in different spin quantum states. We compare the calculated resonant Raman spectra to the nonresonant Raman spectra also calculated from first-principles. |
Monday, March 6, 2023 12:30PM - 12:42PM |
B58.00004: Nuclear spin spectra for ground and excited multiplets of Eu-based magnetic molecule Aleksander L Wysocki, Karolina Janicka, Kyungwha Park Achieving quantum light-spin interfaces in molecular magnets is an exciting prospect with potential applications for nanophotonics and quantum information science technologies. While a selected set of magnetic molecules exhibit optical transitions, the molecular electronic or nuclear spin states tend to strongly couple to surrounding environment in an uncontrollable fashion. This hampers the usage of the molecular spin states for platforms for coherent spin-photon coupling. Recently, super-narrow homogeneous optical linewidths have been experimentally achieved by considering nuclear spin states in an Eu-based molecular crystal [Serrano et al., Nature 603, 241 (2022)] with evidence of their coherent optical control. Here we investigate electronic ground-state and excited-state multiplets, nuclear spin spectra, and optical properties for the Eu-based magnetic molecule by employing ab-initio multireference quantum chemistry methods including spin-orbit coupling. We construct an effective nuclear spin Hamiltonian from first principles and compare the results to the experiment. Furthermore, we explore effects ligand substitution and the mechanisms of decoherence. |
Monday, March 6, 2023 12:42PM - 12:54PM |
B58.00005: Massive 116 GHz Crystal Field Clock Transition in a Tetragonal Molecular Ho(III) Complex Robert Stewart, Anna Celmina, Emma Regincós, Angelos Tsanai, Mark Murrie, Stephen Hill Molecular lanthanide complexes are promising candidates for development of next-generation quantum technologies. In particular, high-symmetry structures can give rise to well-isolated crystal-field quasi-doublet ground states, i.e., quantum two-level systems that may serve as a basis for spin qubits. More importantly, recent work has shown that the coordination environment around the lanthanide can be tailored to produce an avoided crossing, or clock transition within the ground doublet, where the first-order sensitivity to fluctuations in the local magnetic field is suppressed, leading to significantly enhanced coherence times. Here, we employ single-crystal high-frequency electron paramagnetic resonance (EPR) spectroscopy to interrogate a series of new tetragonal molecular Ho(III) complexes. An axial coordination environment with four-fold symmetry gives rise to a ground state mJ = ±8 crystal-field quasi-doublet with clock transitions as large as 116 GHz. Larger clock transition frequencies result in faster qubit dynamics, reducing the time required for implementing quantum logic operations. Additionally, the second-order sensitivity to magnetic field fluctuations decreases with increasing clock transition frequency, potentially enhancing coherence further. |
Monday, March 6, 2023 12:54PM - 1:06PM |
B58.00006: Spin Population Transfer in a Gd3+ Molecular Crystal Studied by Pulsed High-Field EPR Manoj Vinayaka Hanabe Subramanya, Elvin Salerno, Miguel Gakiya, Krishnendu Kundu, Michael Shatruk, Stephen Hill Gd3+ is a spin S = 7/2 ion that has a half-filled 4f7 electron occupancy, with no first order orbital angular momentum. Thus, its eight spin levels are minimally mixed and can typically be considered pure, with very weak zero-field splitting. For these reasons, the spin states of a Gd3+ ion can encode N = 3 addressable qubits (a d = 2N = 8 level qudit), with each ΔmS = ±1 transition being fully allowed via EPR, permitting spin manipulation using resonant microwave pulses. However, the Pulsed EPR spectrometer must meet several key requirements, including: (1) sufficient microwave power to achieve nanosecond time resolution; (2) wide excitation bandwidth and arbitrary waveform shaping in order to rapidly address spectrally separated spin transitions; and (3) high sensitivity for detection of small samples with low spin concentrations. The quasi-optical 94 GHz HiPER spectrometer [1] at the NHMFL meets all of these requirements and additionally allows for in situ crystal rotation. We demonstrate dynamic spin population transfer within the 8S7/2 ground manifold of a molecular Gd3+ complex diluted into an isostructural non-magnetic Y3+ host crystal, paving the way towards implementation of simple quantum logic operations within a d = 8 molecular spin qudit. |
Monday, March 6, 2023 1:06PM - 1:18PM |
B58.00007: Spin relaxation in clock transition in a Lu(II) molecular spin qubit due to phonon Xiaoliang Zhang, Haechan Park, Haiping Cheng, Xiaoguang Zhang We compute the electron spin decoherence and relaxation times T1 and T2 due to spin-phonon coupling at spin clock-transitions in magnetic molecule crystals. The spin Hamiltonian is coupled to phonon motion through the dependences of the Lande tensor, hyperfine interaction tensor and crystal field tensor on atomic displacement. We then solve the Redfield equation of motion for the reduced density matrix, which yields T1 and T2 from the time correlation function(Ref[1]). The calculations are carried out for a Lu(II) molecular spin qubit at the spin clock-transition. |
Monday, March 6, 2023 1:18PM - 1:30PM |
B58.00008: Spin-electric coupling in Fe3 triangular single molecule magnet Fhokrul Islam, Carlo M Canali, Mark R Pederson The frustrated triangular single molecule magnets (SMMs) with half integer spins is an important class of molecular magnet that has potential application as qubits in quantum information processing. The lack of inversion symmetry allows these molecular qubits to be manipulated by an external electric field. Among several candidate triangular molecules, Fe3O(NC5H5)3(O2CC6H5)6 molecular cation is particularly exciting since this is the first triangular SMM in which spin-electric coupling effect is observed experimentally. In this work, we have generalised formalism to calculate chiral ground states of triangular SMMs to account for spin 5/2 SMMs. We also have derived an expression for spin-electric coupling in this SMM that can be calculated using first-principles density functional theory with non-collinear spins as implemented in NRLMOL code. |
Monday, March 6, 2023 1:30PM - 1:42PM |
B58.00009: Tunable clock transitions in lanthanide complexes for quantum information technologies Jakub Hruby, Krishnendu Kundu, Danh Ngo, Ryan Murphy, Randall McClain, Benjamin Harvey, Jeffrey R Long, Stephen Hill Bottom-up chemical synthesis of molecular spin qubit architectures represents a novel way for pursuing next-generation quantum technologies that could substantially influence all fields of human activity from complex structural biology to finance.1,2 Our work focuses on fine-tuning resonant clock transitions (CTs) within 4f n5d1 Ln(II) complexes, such that the associated transition frequencies, f, are insensitive to the local magnetic induction, B0, with df/dB0 → 0 at the CT minimum. This offers protection from magnetic noise and up to 10 times longer phase memory times, Tm, compared to conventional EPR transitions.3 As an added bonus, hyperfine CTs associated with significant s-d mixing in 4f n5d1 Ln(II) complexes minimizes spin-orbit coupling, leading also to enhanced spin-lattice relaxation times, T1.4 |
Monday, March 6, 2023 1:42PM - 1:54PM |
B58.00010: Modeling nonadiabatic spin dynamics in single-ion magnets with crystal field Hamiltonian Vsevolod Dergachev, Daria Nakritskaia, Yuri Alexeev, Sergey A Varganov Predicting spin relaxation and decoherence in single-ion magnets (SIMs) is crucial for designing practical spin-based materials for quantum information science applications, including quantum memory devices and quantum computing. A detailed understanding of the spin relaxation and decoherence pathways, including those mediated by couplings between the vibrational and spin degrees of freedom, is necessary to design new materials with long spin relaxation and coherence times. From the theoretical standpoint, this requires accurate modeling of the long time-scale electron and nuclear dynamics of actual molecular magnets with dozens of atoms, which is outside the capabilities of modern computational methods. To develop such capabilities, we aim to replace the ab initio electronic structure Hamiltonian used in the nonadiabatic molecular dynamics simulations with the crystal field Hamiltonian (CFH). Extremely fast electronic structure calculations with CFH will allow us to model the spin relaxation in large realistic SIMs. To achieve this goal, it is necessary to accurately parametrize CFH and interface it with nonadiabatic molecular dynamics. We will present the current progress on the development of this CFH-based nonadiabatic molecular dynamics to model spin relaxation in SIMs. |
Monday, March 6, 2023 1:54PM - 2:06PM |
B58.00011: Simultaneous excitation of both spins in a molecular nanomagnet dimer Sofia M Davvetas, Charles Collett, Yujin Kim To make a system of multiple spin qubits out of molecular nanomagnets (MNMs), each spin needs to be separately and simultaneously addressable. The simplest such system is a dimer, where two MNMs are physically and magnetically connected in a single molecule. Performing electron spin resonance (ESR) on both spins at the same time requires both bimodal resonators as well as a spectrometer capable of producing and detecting the necessary multi-frequency pulses. We will report recent work our lab has done to simultaneously excite both spins in an MNM dimer, with an end goal of demonstrating quantum gates in this system. |
Monday, March 6, 2023 2:06PM - 2:18PM |
B58.00012: Coherence Enchancement by Clock Transition and Dynamical Decoupling in S=1 Molecular Nanomagnets Guanchu Chen, Grigore Timco, Jillian Denhardt, Kevin Kittilstved, Richard Winpenny, Jonathan R Friedman Cr7M molecular nano-magnets (MNMs) are a group of heterometallic antiferromagnetic rings containing seven Cr ions and a different metal ion. Some species like Cr7Mn and Cr7Co are spin-1 systems in which an avoided level crossing can occur at zero field. The transition between such levels, called clock transition, is insensitive to the fluctuations of the field. We observed enhanced coherence time T2 at the clock transition in Cr7Mn. Dynamical decoupling techniques like CPMG pulse trains enhance the coherence further. Away from zero field, the Cr7Mn MNM exhibits significant Electron Spin Echo Envelope Modulation (ESEEM) signal. The comparable signal size hints at a possible additional mechanisms to preserve coherence away from clock transition through the coupling to nuclear spins. And CPMG sequence allows us to demodulate the signal and measure T2. Consistent with continuous-wave spectra, Cr7Mn shows pulsed EPR signals across a wide range of fields and frequencies, indicating a relatively large inhomogeneity in anisotropy of the system. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700