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 S45: Near-Field Infrared NanospectroscopyFocus
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Sponsoring Units: GIMS Chair: Larry Carr, Brookhaven National Laboratory Room: Room 315 |
Thursday, March 9, 2023 8:00AM - 8:36AM |
S45.00001: Ultrabroadband Infrared Nanospectroscopy Invited Speaker: Hans Bechtel The development of near-field infrared techniques has enabled infrared analysis to surpass the diffraction-limit and probe chemical and physical heterogeneities at the nanoscale. In infrared scanning near-field optical microscopy (IR s-SNOM), IR light is focused onto and scattered by an atomic force microscope (AFM) tip, and detected interferometrically in the far-field with an IR detector. When combined with the broad bandwidth, spatial coherence, and high brightness of synchrotron infrared radiation, IR s-SNOM enables vibrational spectroscopy spanning the infrared region with a wavelength-independent spatial resolution equivalent to the tip-apex radius, which is typically less than 25 nm. The Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory operates two of these synchrotron infrared nanospectroscopy (SINS) instruments that are available for general users to address fundamental questions that can only be answered with a chemically selective nanoscopic probe. In this talk, I will describe the technical aspects of the SINS technique and highlight representative examples of the rapidly growing range of applications in physics, chemistry, biology, materials science, geology, and atmospheric and space sciences. While most of the applications to date have been measured under ambient conditions in the mid-IR, many in situ / in operando measurements require additional environmental control (i.e. variable cryogenic temperatures, gas/vacuum, liquids) and/or increased spectral range in the far- and near- IR that push the current boundaries of our instruments and technique. I will describe efforts to address some of these challenges and offer perspectives for the future of infrared nanospectroscopy. |
Thursday, March 9, 2023 8:36AM - 8:48AM |
S45.00002: New Infrared Nanospectroscopy Endstation at the National Synchrotron Light Source II Lukas Wehmeier, Mengkun Liu, Steven Hulbert, Dmitri N Basov, G.Lawrence Carr Infrared near-field spectroscopy provides unique capabilities for exploration of the nanoworld as it combines the information density of optical techniques with the spatial resolution of atomic force microscopy of ~10 nm. When combined with the high spectral radiance of infrared synchrotron light sources, nanospectroscopy covers an ultrabroadband spectral range from the near to far infrared (320 cm-1 - 8000 cm-1, 40 meV – 1 eV). |
Thursday, March 9, 2023 8:48AM - 9:00AM |
S45.00003: Infrared correlation nanoscopy with unprecedented spectral coverage Tobias Gokus, Stefan Mastel, Artem Danilov, Andreas Huber We demonstrate scattering near-field microsocpy (s-SNOM) imaging and spectroscopy based on a fully integrated and automated commercial OPO laser source covering the spectral range from 1.5−18.2μm (ca. 7100 – 540 cm-1) with narrow linewidth <4 cm-1 in the entire tuning range. To illustrate the capabilities of this light source, a thin hBN flake on a SiO substrate is imaged by s-SNOM with interferometric detection to obtain nanoscale resolved amplitude and phase images of the propagating surface polariton mode. Near-field imaging at 810 cm-1 reveals the characteristic fringe pattern at the edge of the flake, stemming from propagating Surface Phonon-Polaritons (SPhP) in the lower Reststrahlenband, launched by the AFM probing tip. Accessing the lower Reststrahlenband in hBN for nanoscale resolved far-IR s-SNOM imaging and spectroscopy is unique and unprecedented, and is a first demonstration of the capabilities of the presented light source for s-SNOM experiments to study polaritons in different material systems and devices. |
Thursday, March 9, 2023 9:00AM - 9:12AM |
S45.00004: Ultra-broadband cryogenic nanoscopy: The next evolution in tabletop nano-optics Alexander S McLeod, Liam Thompson, William Cho The spatial dimensions natural to many quantum materials ranging from complex oxides to twisted van der Waals multilayers lie characteristically at the nano-scale, which poses a barrier to resolving phenomena in these materials with conventional bulk probes like optical spectroscopy. Thankfully, the recent decade has witnessed rapid development of infrared nano-imaging at cryogenic temperatures, owing to seminal experiments enabled by uniquely designed scanning probe microscopes. To date however, the promise of truly broadband infrared nano-spectroscopy at liquid helium temperatures has remained unfulfilled. In fulfillment of this promise, we present a novel cryogenic Scanning Near-field Optical Microscope (cryo-SNOM) capable of ultra-stable phase-resolved nano-imaging and -spectroscopy at uninterrupted energies spanning the mid-infrared to the visible regime. Our instrument couples a unique balanced asymmetric Michelson interferometer to a high-power fiber feedback-stabilized 40 MHz optical parametric amplifier and difference frequency generation stage, supplying continuous remote energy tuning to enable nano-imaging and spectroscopy interchangeably with push-button simplicity. Moreover, we present a unique scheme integrating remote laser tuning with Fourier transform infrared spectroscopy to supply ultra-broadband spectroscopy spanning 500-2000 cm-1 and beyond. A long-range closed-loop scanner combined with helium cryostat and unique thermal insulation enable reliable operation at temperatures from 10-400K. This next evolution in cryogenic nanoscopy provides an unprecedented combination of low noise and low temperature conditions for the nano-resolved study of quantum matter across a decade of phonon energies. |
Thursday, March 9, 2023 9:12AM - 9:24AM |
S45.00005: RAMBO-II: Ultrabroadband Optical Spectroscopy of Materials in Magnetic Fields Up to 50 T William A Smith, Andrey Baydin, Jiaming Luo, Hiroyuki Nojiri, Aditya Mohite, Ming Yi, Hanyu Zhu, Junichiro Kono Study of a material’s optical properties in high magnetic fields is often complicated by the size, construction, and availability of magnets with excellent optical access. The chief aim of RAMBO – the Rice Advanced Magnet with Broadband Optics – is to enable a wide variety of ultrafast and nonlinear spectroscopy measurements not possible or prohibitively difficult in large DC or pulsed magnet systems by constructing multiple compact, mini-coil-based table-top pulsed magnets with excellent optical access. RAMBO-I has already been used for terahertz time-domain spectroscopy |
Thursday, March 9, 2023 9:24AM - 9:36AM |
S45.00006: Phase-resolved terahertz nano-imaging of WTe2 microcrystals Ran Jing, Rocco A Vitalone, Suheng Xu, Chiu Fan Bowen Lo, Zaiyao Fei, Elliott Runburg, Yinming Shao, Xinzhong Chen, Fabian Mooshammer, Alexander S McLeod, Mengkun Liu, Michael M Fogler, David H Cobden, Xiaodong Xu, Dimitri Basov The terahertz electrodynamics of few-layer WTe2 is dominated by the plasmon response. However, terahertz surface plasmons with long wavelengths in two-dimensional exfoliated crystals are typically confined by the lateral geometry. Direct visualization of the plasmonic standing wave patterns is challenging due to the spatial confinement and low quality factor of the surface plasmon, especially for samples that are only a few monolayers thick. Here, we resolve subtle real-space features of the plasmonic response of WTe2 by augmenting more common scattering amplitude experiments with the phase contrast accomplished within the time-domain version of THz nano-imaging. Amplitude and phase images allow us to quantitatively evaluate the evolution of the plasmonic response at cryogenic temperatures in samples with variable thickness from 3 to 12 monolayers. The proposed imaging modality is universally applicable to the THz near-field nanoscopy of low-dimensional materials. |
Thursday, March 9, 2023 9:36AM - 9:48AM |
S45.00007: Multivalued electro optic response in near-field THz polarimetry Tim LaFave, Andrea G Markelz A robust calibration method to correct instrumentation artifacts in near-field THz polarimetry is reported. An unexpected nonlinear dependence of the NIR quarter waveplate angle with respect to each NIR half waveplate angle was observed in one of two balanced response curves using a time-domain spectroscopy configuration. Signal degradation stems from this multivalued electro-optic response and is associated with an unwanted frequency dependence. Our calibration method removes these artifacts from ZnTe absorbance spectra by normalizing all E-field measurements at every THz polarization angle across the bandwidth of interest (~0.5 – 100 cm-1) and sampling the ZnTe region from which sample measurements are subsequently made. Remaining THz polarization dependencies are additionally removed by normalizing absorbance spectra with respect to the E-field maximum of the reference THz angle spectrum. Reproducible absorbance results were obtained on several triose phosphate isomerase (TPI or TIM) protein crystals with several apertures to sample different regions of the ZnTe crystal. Serendipitously, this method also corrects for previously reported deleterious effects due to defect nonuniformities in ZnTe electro-optic crystals commonly used in near-field polarimetry. |
Thursday, March 9, 2023 9:48AM - 10:00AM |
S45.00008: Micro four-point probe transport measurements on two-dimensional materials Jort Verbakel, Kevin Vonk Usually, electronic transport measurements on two-dimensional materials such as graphene and transition metal dichalcogenides require the deposition of electrodes on top of the material, in for instance the form of a Hall bar device. In this work, we show that by making use of a collinear micro four-point probe, electrical transport measurements on |
Thursday, March 9, 2023 10:00AM - 10:12AM |
S45.00009: Near-field imaging of Q > 50,000 photonic ring resonators in electronics-photonics integrated CMOS platform Mark G Schiller, Kenaish Al-Qubaisi, Bohan Zhang, Deniz Onural, Miloš A Popovic, Michael J Naughton Despite continual progress towards higher Q photonic resonators and more accurate near-field imaging techniques, near-field imaging of high Q photonic resonators has remained a challenge to researchers due to the greatly increased tip-sample interaction1,2,3. We present a novel technique in which we are able to successfully near-field image a Q > 50,000 resonator through careful oxide etching of the backside buried-oxide, which allows one to control the tip-sample distance and thus the tip-sample interaction. |
Thursday, March 9, 2023 10:12AM - 10:24AM |
S45.00010: The High Spectral Radiance, Broadband Synchrotron Infrared and THz Spectroscopy Facility at NSLS-II G.Lawrence Carr, Lukas Wehmeier, Christopher C Homes, Mengkun Liu, Vladimir Martinez, Andrei Sirenko The National Synchrotron Light Source II (NSLS-II) is an advanced, medium energy, 3rd generation synchrotron light source at Brookhaven Nat’l Lab (Upton, LI, NY). One of the newest operating beamlines is 22IR2/MET; designed for mid and far-infrared spectroscopy of solids. Capable of continuous spectral coverage from <10 cm-1 in the low THz range to about 40,000 cm-1 in the near UV, it offers a spectral radiance several hundred times greater than a typical thermal spectrometer source and thus is ideal for low-throughput measurement techniques such as microspectroscopy and spectroscopic ellipsometry. Particularly noteworthy is the capability for broadband infrared nanospectroscopy through the technique of apertureless scattering from an AFM tip. This presentation will briefly describe the beamline’s characteristics, starting from the source through the optical system and the various instrument end stations – now open for User science proposals. See https://www.bnl.gov/nsls2/ for details and information on applying for beamtime. |
Thursday, March 9, 2023 10:24AM - 10:36AM |
S45.00011: Phase Tracking for Accurate Interferometric Measurements of Heterodyne Detected e-SFG Spectra Nasim Mirzajani, Sarah B King, Clare L Keenan, Sarah R Melton Heterodyne detection (HD) is a ubiquitous tool in spectroscopy for the simultaneous detection of intensity and phase of light. As an interference measurement, heterodyne detection hinges on the phase stable relationship between the signal and a local oscillator (LO). Short UV-Vis wavelengths used in electronic spectroscopy are susceptible to phase instability due to drifts in optical path length, posing a challenge for heterodyne detection. We present an interferometric design that utilizes phase modulation of one arm of a Mach Zehnder interferometer to directly measure the phase between the two arms. “Tracking” the phase allows us to correct for errors in the path length difference caused by drifts in the optics, offering unprecedented stability. We have applied this method to measurement of electronic sum frequency generation (e-SFG) spectra in the time domain with lock-in amplification, accessing the weak complex second order susceptibility, χ(2), which reports on interfacial energy states in centrosymmetric media. In conjunction with broadband ultrafast pulses, this method will enable in-situ probing of electronic states and charge transfer dynamics at interfaces between materials. |
Thursday, March 9, 2023 10:36AM - 10:48AM |
S45.00012: Thermometry of microscopic samples at ultra-low temperatures and high magnetic fields. Alexander Donald, Lucia Steinke, Andrew J Woods, Rasul Gazizulin Measuring heat capacity and thermal conductivity of small crystals in the ultra-low temperature regime (< 20 mK) along with high magnetic fields (> 14 T) is challenging due to a lack of suitable thermometers and the small thermal masses of samples. Quartz tuning forks have been shown to be a viable method of temperature measurement of viscous fluids and in particular liquid helium-3 in this extreme regime [1]. This method has been realized for relatively large thermal baths incompatible with measuring thermal effects of small samples. We have designed small capsules of helium-3 to serve as miniaturized and self contained thermometers. Such thermometers provide a way to make local measurements for thermal conductivity or transport. We will discuss techniques for measuring resonance properties in a wide range of conditions from gas to a highly viscous liquid. The simplest method is to measure a resonance curve with a frequency sweep and fit the width of the lorentzian. However, we are exploring alternative techniques such as resonance tracking of the amplitude and ring down measurements and their applicability in different conditions. Our goal is to show that these thermometers and techniques will allow for experiments of thermal properties with novel materials in this difficult to probe regime. |
Thursday, March 9, 2023 10:48AM - 11:00AM |
S45.00013: Advancements in A.C. Magnetic Susceptibility Method at High Pressures Sasanka U Munasinghe, Nugzari Khalvashi-Sutter, Sachith E Dissanayake, Ranga P Dias A superior test for superconductivity is the search for a strong diamagnetic transition in the magnetic susceptibility. With the development of high-pressure novel hydrogen rich, high Tc superconducting materials and their smaller sample size, it is needed to develop a more sensitive measurement techniques for detecting the diamagnetic response. With modern measuring equipment and a new coil design, a significant improvement in sensitivity and SNR was obtained with a constant background over the full temperature range. The coil system includes two identically wound pairs of coils, each pair consisting of a primary and a secondary coil wound on top of each other. The primary coil creates an alternating magnetic field and the secondary coil sense the field. The other pair of coils connected series with opposite polarity to reduce the background. Both the excitation and modulation signals are superpositioned and fed into the primary coil. This eliminates the need for a separate coil for the modulation. Then the signal from the pickup coil is analyzed by a lock-in amplifier in dual reference mode. Extensive studies have been performed to find the optimal frequency and amplitude combinations of the excitation and modulation field on both low-temperature and high-temperature superconductors. |
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