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 F57: Quantum Phenomena and Sensing in Ordered MagnetsFocus
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Sponsoring Units: GMAG Chair: Debanjan Polley, Lawrence Berkeley National Laboratory Room: Room 303 |
Tuesday, March 7, 2023 8:00AM - 8:36AM |
F57.00001: Quantum Sensing and Imaging of Spin Transport and Dynamics in Quantum Materials Invited Speaker: Chunhui R Du Exploring new class of quantum materials with advanced magnetic and electronic properties has been a central focus of modern condensed matter physics over the past decades. The success of these efforts relies simultaneously on advances in theory, material synthesis, and development of new, sensitive metrology tools to characterize the key material properties at the nanoscale. Nitrogen-vacancy (NV) centers, optically active atomic spin defects in diamond, are naturally relevant in this context due to excellent quantum coherence, unprecedented spatial and field sensitivity, and remarkable functionality over broad experimental conditions. Serving as a local probe of multiple degrees of freedom, NV centers are ideally posed to investigate the fundamental correlations between microscopic magnetic textures and the underlying charge, spin, and thermal transport properties of quantum materials. In this talk, I will present our recent work on using NV centers to perform quantum sensing of emergent quantum materials. Specifically, we have utilized NV centers to visualize the exotic spin properties of topological magnetic materials [1-2] and antiferromagnetic insulators [3], revealing the fundamental physics underlying nanoscale spin transport and dynamic behaviors. Taking advantage of NV-magnon based hybrid systems, we also achieved electrical control of coherent NV spin rotations, promoting the role of NV centers at the forefront research of quantum technologies [4]. Lastly, I will briefly discuss our ongoing efforts to explore 2D quantum sensing technologies using emergent color centers beyond NVs [5]. |
Tuesday, March 7, 2023 8:36AM - 8:48AM |
F57.00002: All-diamond scanning probes for high-performance and robust nanoscale magnetometry Felipe Favaro de Oliveira, Gediminas Seniutinas, Marcelo Gonzalez, Brendan Shields, Liza Zaper, Peter Rickhaus, Martino Poggio, Patrick Maletinsky Nitrogen-vacancy (NV) centers in diamonds have emerged as a powerful platform for quantum sensing, enabling highly sensitive and quantitative measurements of magnetic fields both at room and cryogenic temperatures. To achieve nanoscale imaging resolution, scanning NV microscopy has been proposed and developed over the past decade to locally probe stray magnetic fields. This has enabled the revealing of nanoscale domains in multiferroics1 and antiferromagnets2, and even the imaging of a single electron spins3. More recently, such technology is being broadly explored as commercial products started to appear in the market. |
Tuesday, March 7, 2023 8:48AM - 9:00AM |
F57.00003: Image antiferromagnetic order switching using a scanning single-spin microscope Qiaochu Guo, Anthony D'Addario, Yang Cheng, Jeremy Kline, Isaiah Gray, Hil Fung Harry Cheung, Fengyuan Yang, Katja Nowack, Gregory D Fuchs Electrical switching of Néel order in an antiferromagnetic (AF) insulator is desirable as a basis for memory applications. Unlike electrically-driven switching of ferromagnetic order via spin-orbit torques, electrical switching of antiferromagnetic order remains poorly understood. Here we obtain nanoscale magnetic images of a canted AF, α-Fe2O3, using a home-built scanning nitrogen-vacancy (NV) center microscope. We study the change of the magnetic order of α-Fe2O3 induced by an external magnetic field and electric current. Our results show that the orientation of an in-plane 1-Tesla magnetic field influences the sample's magnetic state even after relaxation in a low field. We find that our sample has an overall in-plane uniaxial anisotropy, in contrast to the 3-fold magneto-crystalline anisotropy suggested in previous work. Our observations from the current-induced magnetic order switching experiment indicate that thermo-magnetoelastic effects alone are sufficient to induce magnetic switching in α-Fe2O3 and that spin-orbit torques may not be necessary. |
Tuesday, March 7, 2023 9:00AM - 9:12AM |
F57.00004: Excitation and detection of spin waves in rare-earth garnet insulator TmIG films using diamond nitrogen vacancy magnetometry Abdelghani Laraoui, Rupak Timalsina, Haohan HaohanWang, Adam D Erickson, Bharat Giri, Xiaoshan Xu Study of spin waves, elementary excitations in magnetic materials, can be used as signal carriers in next generation electronic devices [1]. Charge as degree of freedom in devices rather than electron for transferring and representing information eliminates heating effect due to current. Among the currently available techniques, we use ferromagnetic resonance (FMR) detection method to understand the magnetization dynamics, measure the damping, and detect magnon modes in ferrimagnetic insulator Thulium iron garnet (TmIG) films (thickness of 2 -35 nm) made by pulsed laser deposition on gadolinium-gallium-garnet (GGG) substrates. We further use nitrogen-vacancy (NV) center in diamond based magnetometry to measure surface propagating spin waves at the sub-micron scale, seen by the amplification of the local microwave magnetic field due to coupling of NV spin with stray-field produced by the spin waves. We discuss the effects of thickness and substrate (sGGGs vs GGG) on the spin waves properties [2] and outline future experiments on the transport of spin waves and the mechanisms of NV-magnon coupling in TmIG nanostructures, relevant for quantum magnonic applications. [1] A. V. Chumak, et al., Nature Physics 11, 453–461 (2015), [2] R. Timalsina, et al., under preparation. |
Tuesday, March 7, 2023 9:12AM - 9:24AM |
F57.00005: Magnetic field sensing enhancement via triple tone excitation of nitrogen-vacancy center * Romain Ruhlmann, Ankita Chakravarty, Maggie Wang, Vincent Halde, Philip Krantz, Lilian Childress, Michel Pioro-Ladrière Nitrogen-vacancy (NV) centers are powerful magnetic field sensors at room temperature, heralded for their high sensitivity and ease of manipulation, reaching sensitivities sub pT/√Hz [1, 2]. |
Tuesday, March 7, 2023 9:24AM - 9:36AM |
F57.00006: The fate of entanglement in quantum antiferromagnets under Lindbladian dynamics of their localized spins Federico E Garcia-Gaitan, Branislav K Nikolic It is commonly assumed in antiferromagnetic spintronics that localized spins within such materials are in the Neel ground state [1,2] and they obey Landau-Lifshitz-Gilbert (LLG) equation when pushed out of equilibrium by electrons or external fields [3]. However, it is well-known that the ground state of antiferromagnets is highly entangled [4], as confirmed in very recent neutron scattering experiments [5] witnessing their entanglement up to some finite temperature. In this study, we either start from the ground state of quantum Heisenberg antiferromagnet or excited state generated by flipping one of its spins [2], and then evolve them for an open quantum system subject to decoherence [1] and dissipation via the Lindblad quantum master equation obtained [6] by integrating out bosonic bath interacting with the spins. We find that some degree of entanglement always persists, thereby shrinking the length of the vector magnitude of spin expectation values, which makes the LLG equation (operating with classical vectors of localized spins of fixed length) inapplicable. |
Tuesday, March 7, 2023 9:36AM - 9:48AM |
F57.00007: Quantum spin dynamics in a metallic spin chain Ti4MnBi2 Xiyang Li, Mohamed Oudah, Dalmau Reig-i-Plessis, Satyam Priyadarshi, Yipeng Cai, Kenji M Kojima, Naoki Murai, Maiko Kofu, Kenji Nakajima, Masato Matsuura, Hiromu Tamatsukuri, Songxue Chi, Alannah Hallas, Igor A Zaliznyak, Meigan C Aronson One-dimensional spin chain systems provide platforms to explore, both experimentally and theoretically, a wealth of novel quantum phenomena. So far, almost all spin chain systems studied have been insulating. We investigated a new metallic compound, Ti4MnBi2, whose structure consists of chains of S = 1/2 Mn ions that extend along the c-axis. The close spacing of the Mn atoms in the chains and the relatively weak correlations found in heat capacity and susceptibility suggest an antiferromagnetic (AFM) order. We have performed inelastic neutron scattering (INS) measurements using AMATERAS@J-PARC on single-crystal Ti4MnBi2. A gapped magnetic excitation continuum is found roughly between 0.5 and 2 meV unchanged in the AFM state to temperature as low as 0.3 K. The gap decreases above TN, and quasielastic scattering emerges. µSR measurements have been performed at M15/M20D@TRIUMF, finding that 20% of the spins are frozen at temperature below 1K. The µSR, INS, and specific heat measurements all find that substantial magnetic fluctuations persist in the AFM state, an indication of the importance of quantum fluctuations and unconventional AFM order in this system. |
Tuesday, March 7, 2023 9:48AM - 10:00AM |
F57.00008: Magnetic excitations, non-classicality and quantum wake spin dynamics in the Hubbard chain Pontus Laurell, Allen O Scheie, David A Tennant, Satoshi Okamoto, Gonzalo Alvarez, Elbio R Dagotto Recent works have demonstrated that quantum Fisher information (QFI), a witness of multipartite entanglement, and magnetic Van Hove correlations G(r,t), a probe of local real-space real-time spin dynamics, can be extracted from inelastic neutron scattering on spin systems through accurate measurements of the dynamical spin structure factor S(k,ω). Here we apply theoretically these ideas to a fermionic system: the half-filled Hubbard chain with nearest-neighbor hopping. We use DMRG to find S(k,ω), from which QFI and G(r,t) are calculated. The QFI grows with U and can, with realistic energy resolution, witness bipartite entanglement at U≥2.5 (in units of hopping), where it also changes slope. This point is proximate to slope changes of the bandwidth W(U) and half-chain entanglement entropy. The G(r,t) results indicate a crossover in the short-time short-distance dynamics at low U characterized by ferromagnetic lightcone wavefronts, to a Heisenberg-like “quantum spin wake” behavior at large U featuring antiferromagnetic lightcones and spatially period-doubled antiferromagnetism. We find this crossover has largely been completed by U=3. Our results thus provide evidence that, in several aspects, the strong-coupling limit of the Hubbard chain is reached qualitatively already at a relatively modest interaction strength. |
Tuesday, March 7, 2023 10:00AM - 10:12AM |
F57.00009: Dynamic effects of the Dzyaloshinskii-Moriya Interaction in quantum spin dimers Joseph Prescott, Jason T Haraldsen The noncollinear Dzyaloshinskii-Moriya (DM) Interaction has picked up significant interest over the last decade due to the emerging field of Spintronics seeing great potential for the mechanism. Hence, the finding of the effects of the DM Interaction has also been attractive to nanoscale magnetics. Here we uncover the effects of the DM interaction on the well-studied quantum spin dimer for S1 = S2 = 1/2 and 1 by providing analytical solutions to thermodynamic quantities and inelastic neutron scattering to find a structure factor describing the system. Starting with a standard spin-spin exchange Hamiltonian, we introduce an external magnetic field, anisotropy, and the DM interaction. We show that the DM interaction splits energy eigenstates, which alters the thermodynamic quantities, and changes the intensities neutron structure factor for the dimer. |
Tuesday, March 7, 2023 10:12AM - 10:24AM |
F57.00010: Enhanced Magnon-Magnon Entanglement in the Vicinity of Angular Momentum Compensation Point of a Ferrimagnet in a Cavity Kyung-Jin Lee, Jaechul Shim Highly entangled states are the key to the realization of quantum information processing. We theoretically investigate magnon-magnon entanglement in a compensated ferrimagnet. We show that the steady-state magnon-magnon entanglement largely enhances in the vicinity of angular momentum compensation point (TA) when magnons are coupled with photons in a cavity. The origin of this enhancement is that the ground state of ferrimagnet can be close to the Einstein-Podolsky-Rosen state near TA. This feature is unique to ferrimagnets with different Landé-g factors between sublattices and makes the magnon entanglement of ferrimagnets higher than that of ferromagnets and antiferromagnets. |
Tuesday, March 7, 2023 10:24AM - 10:36AM |
F57.00011: Electron-mediated entanglement of two distant macroscopic ferromagnets within a nonequilibrium spintronic device Abhin Suresh, Rafael D Soares, Priyanka Mondal, João Pedro, João M Viana Parente Lopes, Aires Ferreira, Adrian E Feiguin, Petr Plechac, Branislav K Nikolic Using the nascent concept of quantum spin-transfer torque, we predict that a charge current pulse can be harnessed to entangle two spatially separated ferromagnets (FMs) within a spin-valve. The injection of a current pulse endows the spin-valve system with rich nonequilibrium dynamics, where a quantum superposition of many-body states places the spatially separated FM layers into a mixed entangled state. This is due to a transfer of spin angular momentum from conduction electrons to the localized spins via quantum spin-transfer torque that remains active even for collinear but antiparallel arrangements of the two FMs. The dynamical build-up of mixed-state entanglement between the FM layers is quantified by calculating the mutual logarithmic negativity, entanglement entropy, and mutual information over time via fully quantum many-body approaches. The effect of decoherence on our scheme, the use of multi-electron pulses, and the scaling with system size are also analyzed to ascertain the robustness of our predictions under realistic experimental conditions. Finally, we propose a "current-pump/X-ray-probe" scheme, utilizing ultrafast X-ray spectroscopy, which can witness nonequilibrium entanglement of the FM layers by extracting their time-dependent quantum Fisher information. |
Tuesday, March 7, 2023 10:36AM - 10:48AM |
F57.00012: Magnon dynamics in a quantum Heisenberg antiferromagnet Jun-Yi Shan, Kyle Seyler, Mingyao Guo, Chang Jae Roh, Daniel van Beveren, Costel R Rotundu, Young S Lee, Tae Won Noh, David Hsieh In this talk I will introduce different magnon generation mechanisms in a parent compound cuprate using intense laser pulses, and their corresponding magnon relaxation pathways through time-resolved optical second harmonic generation measurements. I will also discuss the consequences on the magnon decaying timescales. |
Tuesday, March 7, 2023 10:48AM - 11:00AM |
F57.00013: Open-source FPGA control for Nitrogen-Vacancy Quantum Sensing Andrew M Mounce, Jacob D Henshaw, Luca Basso, Rong Cong, Pauli Kehayias, Joe M Kitzman, Johannes Pollanen, Fedor F Balakirev, Michael P Lilly The recent release of radio frequency system on chip (RFSoC) FPGA boards opens an opportunity for researchers to implement cheap, fast, custom hardware for quantum sensing, quantum information processing, or complex measurements requiring high precision timing. This has recently been demonstrated through the Quantum Instrumentation Control Kit (QICK) [1] firmware for superconducting qubit control. In this talk, I will show how the QICK framework can be further utilized for nitrogen-vacancy magnetometry from single defects to ensembles. Using our QICK extension, (Defect Arbitrary Waveform Generation, DAWG) can reduce the cost of defect-based quantum sensing and information processing by nearly a factor of 10 but will also enable techniques that are infeasible or impossible with traditional instruments, such as real time feedback for adaptive pulse sequencing. [1] Stefanazzi, L. et al. The QICK (Quantum Instrumentation Control Kit): Readout and control for qubits and detectors. Review of Scientific Instruments, 93, 044709 (2022). |
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