Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session S60: Advances in Scanned Probe Microscopy IIFocus Live
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Sponsoring Units: GIMS Chair: Roger Proksch, Asylum Research |
Thursday, March 18, 2021 11:30AM - 12:06PM Live |
S60.00001: Magnetic sensing and control using single-atom spin resonance in an STM Invited Speaker: Christopher Lutz We combine the atomic resolution of a low-temperature scanning tunneling microscope (STM) with the high energy resolution of electron spin resonance (ESR), to employ individual atoms on a surface as local magnetic sensors [1]. The STM tip drives spin resonance by means of the large electric field available in the tunnel junction, and senses the spin by means of magnetoresistance, using a spin-polarized STM tip. Magnetic dipolar coupling between iron atoms placed a few nanometers apart on a thin MgO film yields a precise measure of the magnetic moment the iron atoms [2], which are then used to sense other atoms, such as the bistable magnetic bits formed by individual holmium atoms [3]. ESR of titanium and copper atoms [4, 5] reveals spin-1/2 behavior, in contrast to the high spin and large magnetic anisotropy of iron. Assembled arrays of spin-1/2 atoms show Heisenberg coupling that results in highly entangled magnetic states. ESR reveals hyperfine coupling [6] that allows electrically driven hyperpolarization of the nucleus [5]. Pulsed ESR allows coherent manipulation of atomic spins in order to observe Rabi oscillations and spin echoes [7]. Recent measurements using thicker insulating films suggest a route to longer coherence times. The combination of STM with ESR thus provides a versatile tool for exploring nano-scale quantum magnetism. |
Thursday, March 18, 2021 12:06PM - 12:18PM Live |
S60.00002: Scanning SQUID microscopy – a powerful tool for quantitative microscale magnetic imaging Huiyuan Man, John Robert Kirtley, Kathryn Ann Moler Nowadays, material science requires precise quantitative microscale measurements of magnetic materials. A Superconducting Quantum Interference Device (SQUID) is the most sensitive detector of magnetic fields available and can be constructed with sub-micrometer dimensions via lithography. A scanning SQUID microscope (SSM) uses a specialized SQUID sensor to image weak local magnetic fields with micrometer spatial resolution. Local susceptibility can be measured using a one-turn field coil integrated into the SQUID sensor to apply a localized magnetic field. We can also reconstruct the 2D current density in the sample from the magnetic flux image above the sample. Three imaging modes are then available: magnetometry, susceptometry, and current imaging. In the NSF funded service center for SSM at Stanford University, magnetic fields of nano Tesla and dipole moments of hundreds of Bohr magnetons are detectable in magnetometry, as well as a volume susceptibility of 10-7 in susceptibility mode and a current of nano amps in current sensing mode. By maintaining thermal separation between the sample and the SQUID sensor, the sample temperature can be varied between 4.3 K and 110 K while scanning. A wide variety of applications of SSM would be included in this talk. |
Thursday, March 18, 2021 12:18PM - 12:30PM Live |
S60.00003: Nanoscale Electric Field Imaging with an Ambient Diamond-NV Scanning Probe Ziwei Qiu, Tony Zhou, Seung Hwan Lee, Patrick R Forrester, Assaf Hamo, Uri Vool, Elizabeth Park, Amir Yacoby The ability of mapping local electric fields is crucial for understanding material's underlying physics. Most current techniques are based on measuring potentials, where cryogenic conditions are usually required to achieve high sensitivity. These include single-electron transistors (SET), scanning tunneling microscopy (STM), Kelvin probe, and scanning capacitance microscopy. Here we demonstrate imaging local electric fields with a scanning nitrogen-vacancy (NV) tip, in the presence of a bias magnetic field perpendicular to the NV axis. The long NV coherence time and atomic size enable high sensitivities and nanoscale resolution (tens of nm) under ambient conditions. This scanning NV electrometry, together with its established magnetic sensing capabilities, provides a new and superior tool for measuring condensed matter phenomena. |
Thursday, March 18, 2021 12:30PM - 12:42PM Live |
S60.00004: Growth of Magnetic Tips by Focused Electron Beam Induced Deposition (FEBID) Javier Pablo-Navarro, Soraya Sangiao, César Magén, JOSE MARIA DE TERESA NOGUERAS The focused electron beam induced deposition (FEBID) technique allows the direct growth of material on any substrate, including cantilevers used in scanning probe microscopy (SPM). Magnetic tips for SPM can be grown by FEBID using precursors of magnetic materials, such as Co2(CO)8 and Fe2(CO)9 [1]. In the current work, we report on the growth conditions to achieve optimized SPM magnetic tips by FEBID for three different applications. In the first application, cobalt magnetic nanospheres are grown for ferromagnetic resonance force microscopy [2]. In the second application, long (10 μm) cobalt nanowires are grown for nanowire magnetic force sensors [3]. In the third application, sharp iron tips are grown for magnetic force microscopy [4]. Novel developments and applications in the field will be discussed. |
Thursday, March 18, 2021 12:42PM - 12:54PM Live |
S60.00005: Ultra-Low Vibration Laboratory based on a Cylindrical Inertia Block Juliet Nwagwu, Wan-Ting Liao, Yu Liu, Joseph D. Gibbons, Jenny E. Hoffman
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Thursday, March 18, 2021 12:54PM - 1:06PM Live |
S60.00006: A crystal oscillator based reactance sensor for Atomic Force Microscopy Ermes Scarano, David Brant Haviland Frequency modulation Atomic Force Microscopy transduces force gradient to frequency shift of an oscillating probe driven on resonance in a phase locked loop. The technique allows for enhanced sensitivity while overcoming the bandwidth limitations associated with high-Q resonators. The sensitivity of the transducer is limited by noise in the external instrumentation typically used to detect the deflection, amplify the signal, and actuate the probe. We propose an alternative transducer concept modeled on the oscillator-based reactance sensor. The reactive element in the oscillator circuit is an AlN piezoelectric length extension resonator operating at radio frequency. The tip-surface force gradient alters the motional capacitance, or effective mechanical stiffness of the piezoelectric resonator, resulting in a relative shift of the oscillation frequency. In our proposed transducer design the sensivity is limited by the phase noise of the oscillator circuit. A sensor-reference oscillator pair form a differential frequency measurement scheme to reject common mode noise and maximize responsivity to frequency shift. The compact architecture is well suited to low temperature and ultra-high vacuum. |
Thursday, March 18, 2021 1:06PM - 1:18PM Live |
S60.00007: Proposed high Q nanocantilever force sensor actuated by the Lorentz force acting on an
integrated superconducting nanoinductor. James Slinkman Annunziata et al.[1] have developed and characterized superconducting nanoinductors which are fabricated on sapphire substrates using standard processes. These nanoinductors consist of Nb or NbN wires on the order of 100 nm wide folded into serpentine layouts. The inductances below the critical temperature are of order 1 nH um -1 . It is proposed here to integrate these nanoinductors rather on a silicon on insulator (SOI) substrate. Standard SOI processing, including the backside, can be used to form the nanoinductors on the free end of a cantilever. Wiring and transmission lines are easily formed for connections DC and RF sources and monitoring outputs. Used as an AFM, force sensing is straightforward. In operation, the cantilever devices are subjected to a DC magnetic field, B, oriented along the length axis. Imposing DC and RF currents actuate mechanical oscillation via the Lorentz force. Both RF and mechanical Q will be higher in the superconducting state. Interesting new physics should emerge related to sensing above and below the critical field and/or the critical B field. [1] Anthony Annunziata et arXiv:1007.4187 |
Thursday, March 18, 2021 1:18PM - 1:30PM Live |
S60.00008: Probing resonating valence bond states in artificial quantum magnets using scanning tunneling microscopy Kai Yang, Soo-Hyon Phark, Yujeong Bae, Taner Esat, Philip Willke, Arzhang Ardavan, Andreas Heinrich, Christopher Lutz Designing and characterizing the many-body behaviors of quantum materials represents a prominent challenge for understanding strongly correlated physics and quantum information processing. We constructed artificial quantum magnets on a surface by using spin-1/2 atoms in a scanning tunneling microscope (STM). These coupled spins feature strong quantum fluctuations due to antiferromagnetic exchange interactions between neighboring atoms. To characterize the resulting collective magnetic states and their energy levels, we performed electron spin resonance (ESR) [1] on individual atoms within each quantum magnet. This gives atomic-scale access to properties of the exotic quantum many-body states, such as a finite-size realization of a resonating valence bond state. The tunable atomic-scale magnetic field from the STM tip allows us to further characterize and engineer the quantum states [2]. These results, combined with pulsed ESR [3], open a new avenue to designing and exploring quantum magnets at the atomic scale for applications in spintronics and quantum simulations. |
Thursday, March 18, 2021 1:30PM - 1:42PM Live |
S60.00009: The direct link between inter-particle force profiles and bulk rheology in dense suspensions: An experimental evidence using tuning-fork AFM. Anh Vu NGUYEN LE, Guillaume Ovarlez, Annie Colin Dense suspensions are soft-matter systems that might display not-fully-understood and complex flow behaviors (e.g. shear thickening, shear thinning). The microscopic interactions between the particles – especially pairwise frictional forces – can play a decisive role in explaining the bulk rheology of suspensions in dense regime. |
Thursday, March 18, 2021 1:42PM - 1:54PM Live |
S60.00010: Design of a Room Temperature AFM Christopher Kochis, Sagar Bhandari An Atomic Force Microscope (AFM) is very important in helping to discover properties of quantum materials that have huge applications to society and have paved the way for fundamental scientific breakthroughs. Although there are many commercial AFMs available, most of them are expensive and not affordable to an undergraduate institution. Our motivation is to build a low-cost room temperature AFM that would allow undergraduate institution like ours to do research on quantum materials. AFM is essentially made up of a closed loop feedback system consisting of a piezo tube, cantilever tip, and a coarse positioning system. Without a thorough mechanical design utilizing each of these parts, this instrument would be useless. Before constructing a room temperature model, it is important to test mechanical parts like the coarse positioning system, which is essential to the design. We present design and implementation of a low-cost room temperature AFM. This AFM allows for quantum imaging experiments in an affordable way. |
Thursday, March 18, 2021 1:54PM - 2:06PM Live |
S60.00011: Cooled Scanning Probe Microscopy of Electrons in Quantum materials Sagar Bhandari, Andrew Smeltzer, Kyle Sayre, Christopher Kochis, Donivan Mouck, Michael Zirpoli Quantum materials such as graphene, transition metal dichalcogenides (TMDCs) and topological insulators are excellent candidates for new electronics and photonics based on quantum mechanics. To understand their physics, it is crucial to know how electrons move through them. In this talk, I will present design of a liquid Nitrogen cooled scanning probe microscope (SPM) that allows us to probe local electronic properties of such quantum materials. Electronic properties such as trajectory of electrons, local density of states and quantum capacitance can be measured with a capacitively coupled SPM tip. An image is obtained by displaying the change in conduction or capacitance as the tip is raster scanned across the sample. We plan to use this tool for quantum materials research at an undergraduate institution. The results from such experiments will help us understand device physics in quantum materials to develop quantum devices such as quantum sensors. |
Thursday, March 18, 2021 2:06PM - 2:18PM Live |
S60.00012: A scanning quantum cryogenic atom microscope at 6 K Stephen Taylor, Fan Yang, Brandon A Freudenstein, Benjamin L Lev The Scanning Quantum Cryogenic Atom Microscope (SQCRAMscope) is a quantum sensor in which a quasi-1D quantum gas images electromagnetic fields emitted from a nearby sample. We report improvements to the microscope. Cryogen usage is reduced by replacing the liquid cryostat with a closed-cycle system and modified cold finger, and cryogenic cooling is enhanced by adding a radiation shield. The minimum accessible sample temperature is reduced from 35 K to 5.8 K while maintaining low sample vibrations. A new sample mount is easier to exchange, and quantum gas preparation is streamlined. |
Thursday, March 18, 2021 2:18PM - 2:30PM On Demand |
S60.00013: Controlled Manipulation of Molecules on Metal Surfaces – Case Study of Benzene on Cu (001) Omur Dagdeviren, Chao Zhou, Milica Todorovic, Eric I. Altman, Udo Dietmar Schwarz With the continued development of scanning probe microscopy techniques, the manipulation of single molecules has become possible. Thereby, the manipulation path can be chosen at will, and energy barriers can be quantified, as can the energy landscape around the molecule [1]. The molecules were either pushed, pulled, jumped to the tip, or did not move depending on the chemical surrounding of the molecule and the chemical identity of the tip. To preserve the accuracy of recovered tip-sample interaction, we used oscillation amplitudes significantly larger than the decay length of the tip-sample interaction potential [1-3]. For further insight, we compared measured energy landscapes and manipulation outcomes with computational results obtained using a search protocol [4]. References: [1] O. E. Dagdeviren et al., Nanotechnology 27 (2016). [2] O.E. Dagdeviren et al., Phy. Rev. App. 9 (2018). [3] O. E. Dagdeviren et al., Rev. of Scien. Ins. 90 (2019). [4] M. Todorovic et al. npj Comp Mat. 5 (2019). |
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