Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session S31: Microscopy 2: X-Rays, Neutrons, ScannedRecordings Available
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Sponsoring Units: GIMS Chair: Melissa Santala, Oregon State Room: McCormick Place W-192A |
Thursday, March 17, 2022 8:00AM - 8:12AM |
S31.00001: Study of Crystal Defects Using Dark-Field X-ray Microscopy Combined with High-Energy Diffraction Microscopy and Computer Vision Jayden C Plumb, Zahir Islam, Peter Kenesei, Zhan Zhang, Ishwor Poudyal, Zhi Qiao, Rebecca L Dally, Samantha Daly, Stephen D Wilson Functional materials display magnetic, electronic and thermal properties that are intimately linked to their crystal structure. These crystalline structures are inherently imperfect, and their defects generate variations in local strain and orientation which impacts their macroscopic properties. The characterization of these defects, especially on the 'mesoscale', is a necessary step towards understanding their effect on material behavior. Here, we report on the use of dark-field x-ray microscopy (DFXM) and high-energy diffraction microscopy (HEDM) techniques to collect rich (~10 TB) experimental data to characterize the mosaic and strain state of a highly twinned and intergrown crystal structure. The measured sample was a single crystal of the known, highly faulted cathode material, NaMnO2. The wealth of information stored within this data is only accessible by leveraging computational resources and machine learning algorithms. An optical flow algorithm is being employed for motion correction, with plans to implement additional AI methods for defect identification and classification. Additionally, the correlation of DFXM and HEDM data is a first-of-its-kind study at the APS, defining a novel methodology for collecting crystal structure information across multiple length scales. |
Thursday, March 17, 2022 8:12AM - 8:24AM |
S31.00002: Coherent-Enhanced Dark Field Imaging for Structural Heterogeneity in Materials Ishwor Poudyal, Zahirul Islam, Stephan O Hruszkewycz, Siddharth Maddali The greatly enhanced coherent X-ray flux enabled by fourth-generation facilities like the upcoming Advanced Photon Source Upgrade (APS-U) will open the possibility of new ways to characterize crystalline materials when combined with established methods like lens-based dark-field X-ray microscopy (DFXM). The geometric and topological signatures of lattice heterogeneities in such materials are encoded in the Bragg-diffracted coherent wavefields which subsequently pass through a lens system and are then incident upon an area detector. These measured intensity distributions correspond to the structural information of the material in real/reciprocal phase space when recorded between the back focal plane of the lens (Fourier-space image) and the conventional image plane (real-space). We describe initial defocus-regime simulations of such “fractionally” propagated coherent Bragg diffraction as a means to understand how to enhance signatures of the crystal defect fields in a crystalline sample. Our preliminary full-field simulation results support the feasibility of such “coherence-enhanced DFXM” for the characterization of defects by exploiting the enhanced contrast. Such contrast enhancement through this adaptation of the DFXM methodology presents complementary to other methods of materials imaging in terms of sub-second materials dynamics and is poised to exploit the greatly enhanced coherence of upcoming fourth-generation synchrotron light sources. |
Thursday, March 17, 2022 8:24AM - 8:36AM |
S31.00003: Single Atom X-ray Spectroscopy using Synchrotron X-rays Scanning Tunneling Microscopy Saw W Hla, Tolulope M Ajayi, Daniel J Trainer, Sanjoy Sarkar, Nozomi Shirato, Daniel Rosenmann, Shaoze Wang, Volker Rose X-rays are produced by excitations of the core level electrons in atoms, and they are useful to detect the type of elements in the periodic table. However, X-ray characterization generally requires a large number of atoms to attain a detectable signal and reducing the size of a sample for X-ray experiments is a long-time goal. To date, X-ray detection of materials can be made on the samples with as few as ~104 atoms due to advances in instrumentation. Here, we show that X-rays can be used to detect metal atoms at the ultimate atomic limit in a quantum tunnelling regime: A single iron atom caged in an organic host, a hexagonal shape supramolecule, has been detected using synchrotron X-ray scanning tunneling microscopy. The experiments were conducted at the XTIP beamline [1] located at the sector 4-ID-E of the Advanced Photon Source of Argonne National Laboratory. Using a specialized coaxial tip positioned at the extreme proximity to the molecule as a detector, the photocurrent generated from the synchrotron X-ray excitation of the iron atom is recorded. The fingerprints of the iron atom, the L3 and L2 edge signals at 708.9 eV and 722.1 eV energies originating from the 2p 3/2 and 2p ½ to ‘d’ transitions, are directly observed in the X-ray absorption spectra. |
Thursday, March 17, 2022 8:36AM - 8:48AM |
S31.00004: Low-dose differential x-ray phase contrast imaging with single mask geometry and photon counting detectors Mini Das, Jingcheng Yuan X-ray phase contrast imaging (PCI) is being investigated for the potential to image weakly absorbing objects such as soft tissues. Single-mask edge-illumination (EI) is a promising method of x-ray phase contrast imaging with the ability to obtain both absorption image and differential phase contrast image in a single shot with simpler experimental setup and lower x-ray dose compared with traditional double-mask edge-illumination method. In this work, we will propose new model based on TIE for double-mask and single-mask edge illumination method and discuss the design considerations for the single-mask imaging system, such as mask design, X-ray focal spot size and system geometry, to maximize the contrast, SNR, and dose efficiency, etc. We will show the benefits of these approaches when also incorporating cutting edge photon counting detectors where spectral information of detected photons can be readily obtained. |
Thursday, March 17, 2022 8:48AM - 9:00AM |
S31.00005: Fabrication of Gratings for Neutron and X-ray Interferometry with the Ability to Adjust the Period in Real-Time Sarah M Robinson, Ryan P Murphy, Jacob M LaManna, Caitlyn M Wolf, Youngju Kim, Katie M Weigandt, Daniel S Hussey, Nikolai N Klimov We describe the development of a neutron and x-ray transmission grating whose period can be adjusted in near real-time to serve as a suitable source grating for far field interferometry. Our DynAmic ReconfIgUrable Source grating (DARIUS) is fabricated on a silicon platform by patterning and etching microchannels to create a microfluidic device. DARIUS will allow for selectively infilling the microfluidic channels with an x-ray/neutron absorbing fluid to reconfigure the effective grating period on demand. This method enables neutron and/or x-ray beam modulation in real-time. We will report on the initial prototype DARIUS which is comprised of 128 active microchannels etched in silicon with a 20 µm period and 125 µm depth. We will provide details on the fabrication and scaling up to a final device consisting of two gratings patterned on both sides of the wafer, with an active area of 51.2 mm × 51.2 mm and 2,560 channels on each side. The dual-sided DARIUS will be used for dynamic tuning of the effective transmission grating period from 20 µm to 20,000 µm. We also will report progress on wafer-scale bonding to seal the channels with open access ports for selective filling and draining the opaque fluid. |
Thursday, March 17, 2022 9:00AM - 9:12AM |
S31.00006: High-quality X-ray optics characterization using advanced at-wavelength metrology Zhi Qiao, Xianbo Shi, Zahir Islam, Lahsen Assoufid The availability of advanced at-wavelength characterization tools and methods is critical to develop and fabricate the high-quality focusing optics required to achieve diffraction-limited focusing in many instruments deployed at modern X-ray light sources. Existing methods, such as X-ray grating-based interferometry, suffer from low sensitivity and low spatial resolution. Here, we describe a new method, based on coded phase masks and called CMMI [1], that allows one to characterize focusing optics with high sensitivity and excellent spatial resolution, which could be also used in many imaging applications. We used CMMI to characterize polymer-based lenses designed as a high-magnification objective in a full-field X-ray microscope [2]. The measured phase wavefront shows that polymeric lenses with a short focal length have phase errors and aberrations comparable to those of state-of-the-art beryllium lenses. The data can be used to fabricate phase correctors to compensate for phase aberrations and achieve near-ideal focusing. |
Thursday, March 17, 2022 9:12AM - 9:24AM |
S31.00007: Atomically resolved terahertz scanning tunneling spectroscopy as a tool for exploring new materials Spencer E Ammerman, Vedran Jelic, Yajing Wei, Nathan Everett, Vivian N Breslin, Mohamed Hassan, Sheng Lee, Stefanie Adams, Trevor Hickle, Kaedon Cleland-Host, Tyler L Cocker Lightwave-driven scanning tunnelling microscopy achieves exquisite spatio-temporal resolution through coherent control of tunnel currents with the oscillating field of a single-cycle light pulse. It was first demonstrated at terahertz frequencies [1], which are particularly well suited to such strong-field control [2,3]. Terahertz scanning tunnelling microscopy (THz-STM) has subsequently been used to resolve the picosecond motion of single molecules [4-6] and extreme tunnel currents through single silicon atoms [7], among other exciting recent results [3]. Thanks to its combination of ultrafast temporal resolution with atomic spatial resolution, THz-STM promises further breakthroughs, especially as a tool for exploring new materials. Yet, its unique view also necessitates a deep understanding of how THz-STM measurements relate to the underlying physics of the system, as the phenomena in question may not be visible to any other experimental technique. Here, we establish an experimental [8] and theoretical [9] framework for atomically resolved terahertz scanning tunnelling spectroscopy, which we believe will be a key modality for future studies. |
Thursday, March 17, 2022 9:24AM - 9:36AM |
S31.00008: Hybrid Machine Learning for Scanning Near-Field Optical Spectroscopy Xinzhong Chen, Ziheng Yao, Suheng Xu, Alexander S McLeod, Stephanie Gilbert Corder, Yueqi Zhao, Makoto Tsuneto, Hans A Bechtel, Michael C Martin, G L Carr, Michael M Fogler, Stefan Stanciu, Dmitri N Basov, Mengkun Liu The underlying physics behind an experimental observation often lacks a simple analytical description. This is especially the case for scanning probe microscopy techniques, where the interaction between the probe and the sample is nontrivial. Realistic modeling to include the exact details of the probe is widely acknowledged as a challenge. Due to various complexity constraints, the probe is often only approximated in a simplified geometry, leading to a source for modeling inconsistencies. On the other hand, a well-trained artificial neural network based on real data can grasp the hidden correlation between the signal and the sample properties, circumventing the explicit probe modeling process. In this talk, we discuss that, via a combination of model calculation and experimental data acquisition, a physics-infused hybrid neural network can predict the probe–sample interaction in the widely used scattering-type scanning near-field optical microscope. This hybrid network provides a long-sought solution for accurate extraction of material properties from tip-specific raw data. The methodology can be extended to other scanning probe microscopy techniques as well as other data-oriented physical problems in general. |
Thursday, March 17, 2022 9:36AM - 9:48AM |
S31.00009: Double resonance of two-coupled s = 1/2 electron spins on a surface using STM Soo-hyon Phark, Yi Chen, Christoph Wolf, Hong T Bui, Yu Wang, Masahiro Haze, Jinkyung Kim, Christopher P Lutz, Andreas J Heinrich, Yujeong Bae Atomic-scale control of multiple spins with individual addressability enables the bottom-up design of functional quantum devices. Tailored nanostructures can be built with atomic precision using scanning tunneling microscopes [1]. However, quantum-coherent driving was limited to a spin in the tunnel junction [2]. Here we show the ability to drive and detect the spin resonance of a remote spin using the electric field from the tip and a single-atom magnet placed nearby. The remote spin was weakly coupled to a second spin that was read out by the tunnel current and acted as a quantum sensor. We simultaneously and independently drove the sensor and remote spins by two radio frequency voltages in double resonance experiments, showing promise for multi-spin manipulation in customized spin structures on surfaces. [1] K. Yang et al. Nat. Commun. (2021); [2] K. Yang et al. Science (2019) |
Thursday, March 17, 2022 9:48AM - 10:00AM |
S31.00010: Characterization of STM-based double resonance of coupled two spins Hong T Bui, Jinkyung Kim, Christoph Wolf, Yu Wang, Masahiro Haze, Yi Chen, Yujeong Bae, Christopher P Lutz, Andreas J Heinrich, Soo-hyon Phark Using a scanning tunneling microscope (STM) combined with electron spin resonance (ESR), we performed electron-electron double resonance on two S = 1/2 Ti atoms on MgO surface. One (Ti(1)) was positioned under the tip, and the other (Ti(2)) was away from the tip and coupled with Ti(1) by a weak interaction [1]. Quantitative understanding on the spectral features and underlying spin dynamics requires a combined study with simulations based on a model such as open quantum system. First, we observed splitting of each double resonance peak, which was linearly increasing with the driving RF voltage. We attribute these features to the AC Stark effect [2], directly providing the Rabi rates of both spins. With these Rabi rates as inputs, simulations of double resonance spectra within the frame of Lindblad formalism [3] let us estimate the energy relaxation times of both spins (T1(1) = 8 ± 2 ns, T1(2) = 150 ± 10 ns). In contrast to the fast relaxation of Ti(1) in the tunnel junction, the much longer relaxation of Ti(2) sheds light on possible use of such 'remote' spins as qubits on surfaces. In addition, we briefly discuss spin decoherence processes in this system. [1] Phark et al. arXiv:2108.09880 (2021); [2] Autler and Townes, Phys. Rev. (1955); [3] D. Manzano, AIP Advances (2020). |
Thursday, March 17, 2022 10:00AM - 10:12AM |
S31.00011: Vector control of quantum superposition states of a single spin on surface using STM Yu Wang, Masahiro Haze, Hong T Bui, Arzhang Ardavan, Soo-hyon Phark, Andreas J Heinrich The combination of scanning tunneling microscopy (STM) and electron spin resonance (ESR) provides a tool for qubit control on surfaces. So far, coherent control of such qubits has been achieved on individual atoms [1] and molecules [2], but without a phase control. Here we implemented phase-controlled radio-frequency (RF) pulses in our pulsed ESR experiments. Rabi oscillation data without a phase control demonstrated that our signal was dominated by DC detection, i.e., z-projected qubit state. Measurements on Ti (S=1/2) atoms on a MgO surface with the phase control scheme resulted in ESR signal that oscillated with the RF phase, which directly proved a coherent rotation of the qubit state controlled with the rotation axis. In addition, we performed CPMG sequence and obtained longer coherence time than that from a Spin-echo scheme. We also present a STM-based possible approach to quantum gate operation of a single qubit, paving a way for complete control of its superposition states. |
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