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 D25: Ultrafast Dynamics and Control of Quantum MaterialsFocus
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Sponsoring Units: DLS Chair: Robert Kaindl, Arizona State University Room: Room 217/218 |
Monday, March 6, 2023 3:00PM - 3:36PM |
D25.00001: Tracking magnon propagation with space/time resolved polarimetry Invited Speaker: Joseph W Orenstein The propagation of spin waves in magnetically ordered systems has emerged as a potential means to shuttle quantum information over large distances. An important subset of these systems are "easy-plane" magnets in which the spins are oriented parallel to the planes but without a preferred direction within the plane. In this talk, I describe an experimental and theoretical study of the easy plane ferromagnet Fe3Sn2, in which magnetism arises from a Kagome lattice of Fe ions. Our measurements utilize temporal and spatially resolved optical techniques to launch and detect spin wavepackets, providing quantitative information on their amplitude, frequency, and phase. Conventionally, the arrival time of a spin wavepacket at a distance, d, is assumed to be determined by its group velocity, vg. Surprisingly, we observe the arrival of spin information at times significantly less than d/vg. We show that this spin wave "precursor" phenomenon originates from the interaction of light with the unusual spectrum of magnetostatic modes in Fe3Sn2. Related effects may have far-reaching consequences toward realizing long-range, ultrafast spin wave transport in both ferromagnetic and antiferromagnetic systems. |
Monday, March 6, 2023 3:36PM - 3:48PM |
D25.00002: Chiral phonon-induced spin polarization Jiaming Luo, Tong Lin, Junjie Zhang, Rui Xu, Xiaotong Chen, Boris I Yakobson, Hanyu Zhu Controlling spins on very short time scales e may enable novel non-equilibrium magnetic physics as well as ultrafast spintronics for energy-efficient information processing. Strongly driven phonons directly influence the interatomic distances, orbital symmetry, and exchange interactions that are closely related to magnetism in materials. We excited chiral phonons using circular-polarized terahertz pulses and observed a prominent transient magneto-optic Kerr effect in rare-earth trihalides. The temperature dependence of the spin dynamics indicates a strong magnetic field generated by the phonons. Our result may open a new route to investigate spin-phonon interaction in ultrafast magnetism directly. |
Monday, March 6, 2023 3:48PM - 4:00PM |
D25.00003: Selective generation of strain waves in optomagnet Fe2Mo3O8 You Hua Li, Cheng Ping Chang, Takashi Kurumaji, Yoshinori Tokura, Yu Miin Sheu We have previously demonstrated optomagnet effects in antiferromagnetic Fe2Mo3O8 with selective excitations. An energy selection comes from different crystal fields, i.e., Fe2+ on octahedral (O-) or tetrahedral (T-) site, while a helicity selection arises from antiferromagnetic ordering. Selective excitations also display drastic differences in time-resolved reflectivity between a magnetic ordered and disordered state when a strain wave forms and propagates into bulk. The strain propagation induces interferences of a probe beam that forms oscillatory signal where amplitudes and initial phases have strong correlations with the magnetic ordering, indicating a potential magnetoelastic coupling. Besides, the magnetic correlation varies between O-site and T-site excitation, implying different couplings originating from the two sites. Our study on selective generation of strain waves will provide innovative technology to the development of spin-acoustic devices. |
Monday, March 6, 2023 4:00PM - 4:12PM |
D25.00004: Controllable Coherent Transverse Acoustic Phonon Generation in Jahn-Teller active spinel FeCr2O4 Yan Cheng Chen, Yi Ming Chang, Kaneko Yoshio, Yoshinori Tokura, Yu Miin Sheu Light-generation of coherent acoustic phonons by ultrafast laser has drawn enormous attention due to its wide spectrum of applications. Among most of the reported studies, the dominant generated coherent strain is propagating at longitudinal acoustic (LA) speed rather than at transverse acoustic (TA) speed, limiting potential applications of this technique. Utilizing FeCr2O4, a magnetic material with spinel structure and Jahn-Teller effect, we observed coherent strain propagating at both LA and TA speed. Comparing different excitations, we find the use of on-site d-d transition from Jahn-teller active ions (Fe2+) is a key to generating the TA strain. Furthermore, we demonstrate a precise control of vibrational phase by changing a relative angle between a linear pump polarization and the Jahn-teller distortion, which cannot be achieved via a coherent LA strain generation. The phase control remains robust even under strong magnetic fields, opening up a new opportunity for developing high precision optoacoustic applications. |
Monday, March 6, 2023 4:12PM - 4:24PM |
D25.00005: Evidence for spin correlation-driven exciton formation in iridate Mott antiferromagnets Yuchen Han, Omar Mehio, Zachary Porter, Stephen D Wilson, David Hsieh Coulomb-bound excitons in rigid band semiconductors have been extensively studied for their influence on the optical and optoelectronic properties of semiconductor devices, as well as for testing fundamental quantum many-body phenomena. However, excitons in strongly correlated two-dimensional antiferromagnetic Mott-Hubbard insulators, which are predicted to feature a spin-driven binding force, are still relatively under-explored. Here, we report pump-probe time-domain THz spectroscopy measurements on the Ruddlesden-Popper iridate Mott antiferromagnets Sr2IrO4 and Sr3Ir2O7, revealing signatures of transient Hubbard excitons. Moreover, by monitoring the behavior of intra-excitonic transitions across their antiferromagnetic ordering temperatures, we observe that the existence of these Hubbard excitons depends critically on the in-plane antiferromagnetic correlations. Our findings provide experimental evidence of a spin-based exciton binding mechanism in Mott antiferromagnets, possibly leading to new directions for exciton creation and control. |
Monday, March 6, 2023 4:24PM - 4:36PM |
D25.00006: Quantum-Geometric Light-Matter Interactions and Light-Induced Phases in Moiré Heterostructures Martin Claassen, Wai Ting Tai Irradiation with light provides a powerful tool to interrogate, control or induce new quantum states of matter out of equilibrium, however a microscopic understanding of light-matter coupling in interacting electron systems remains a profound challenge. Here, we show that THz radiation grants a new quantum-geometric handle to steer and probe correlated quantum materials, whereby light dynamically dresses the Wannier functions of interacting electrons which govern the low-energy dynamics, permitting a direct light-induced modulation of electronic interactions. Notably, this effect appears in any interacting electron system, but dominates optical properties in quantum materials with non-trivial quantum geometry or topology which host bands with poorly-localized or obstructed Wannier functions. We discuss ramifications for optical responses of twisted bilayer graphene and twisted transition-metal dichalcogenides and show that ultrafast THz pump-probe experiments provide a new avenue to explore the rich phase diagram of these materials and stabilize competing phases out of equilibrium. |
Monday, March 6, 2023 4:36PM - 4:48PM |
D25.00007: Ultrafast Vectorial Currents in Nanoscale Symmetry-Controlled Optoelectronic Metasurfaces Jacob A Pettine, Teng Shi, Kevin W Kwock, Luke McClintock, Rohit P Prasankumar, Antoinette J Taylor, Prashant Padmanabhan, Hou-Tong Chen Controlled charge flow underpins nearly all modern information technologies, while ultrafast vectorial nanoscale currents provide new opportunities in high-frequency nanoelectronics, transient symmetry control, nano-magnetism, electron hydrodynamics, and terahertz science. Clearly, the conventional paradigms of integrated circuits are limited in terms of versatility, speed, and active control, while emerging optoelectronic paradigms remain limited in terms of scalability and complex light-matter interaction configurations. Here we demonstrate a new class of optoelectronic metasurfaces that overcome many of these challenges by combining nanoscale patterning with a high degree of active optical control. Nanoplasmonic excitations of symmetry-broken gold antennas serve to drive directional photothermoelectric currents in underlying graphene monolayers, with local (unit cell) symmetries designed for versatile optical responses and corresponding local and global (millimeter-scale) current distributions. Polarization- and frequency-dependent optical responses for different unit cell symmetries offer direct sensitivity to these optical parameters in integrated graphene photodetection applications. Intriguingly, despite the relatively low-quality, large-area graphene utilized here, simulations suggest a new regime of ultrafast-induced electron hydrodynamic behaviors and nanoscale vortical flows. These results suggest additional and more general opportunities for designer control over ultrafast, nanoscale vectorial charge flow in a variety of applications and hybrid systems. |
Monday, March 6, 2023 4:48PM - 5:00PM |
D25.00008: Light-field control of real and virtual charge carriers Ignacio Franco, Tobias Boolakee, Christian Heide, ANTONIO J GARZON RAMIREZ, Heiko Weber, Peter Hommelhoff Light-driven electronic excitation is a cornerstone for energy and information transfer. In the interaction of intense and ultrafast light fields with solids, electrons may be excited irreversibly, or transiently during illumination only. As the transient electron population cannot be observed after the light pulse is gone, it is referred to as virtual, whereas the population that remains excited is called real. Virtual charge carriers have recently been associated with high-harmonic generation and transient absorption, but photocurrent generation may stem from real as well as virtual charge carriers. However, a link between the generation of the carrier types and their importance for observables of technological relevance is missing. Here we show that real and virtual charge carriers can be excited and disentangled in the optical generation of currents in a gold–graphene–gold heterostructure using few-cycle laser pulses. Depending on the waveform used for photoexcitation, real carriers receive net momentum and propagate to the gold electrodes, whereas virtual carriers generate a polarization response read out at the gold–graphene interfaces. On the basis of these insights, we further demonstrate a proof of concept of a logic gate for future lightwave electronics. Our results offer a direct means to monitor and excite real and virtual charge carriers. Individual control over each type of carrier will markedly increase the integrated-circuit design space and bring petahertz signal processing closer to reality. |
Monday, March 6, 2023 5:00PM - 5:12PM |
D25.00009: Light-induced band asymmetries seen by trARPES and their excitonic origin Yi Lin, Yang-Hao Chan, Woojoo Lee, Chih-Kang Shih, Steven G Louie, Alessandra Lanzara We studied photoexcited band structure and ultrafast phenomena in bulk MoS2 by using extreme-UV time- and angle-resolved photoemission spectroscopy (XUV-trARPES). We observed a light-induced transient spectral signature near valence band maximum with explicit asymmetric distributions in energy and momentum, featuring an unusual two-component decay behavior. We conducted theoretical calculations to understand these observations. We found that the excitonic correlations between electrons and holes play the critical role in understanding these light-induced band asymmetries consistently in energy, momentum, and time. Our work provides a new frame for studying ultrafast excitonic phenomena in optically dark materials, such as bulk semiconductors and excitonic insulators, by using photoelectron spectroscopy. |
Monday, March 6, 2023 5:12PM - 5:24PM |
D25.00010: Discovery and Characterization of a Novel Lattice Instability in SnSe Yijing Huang, Shan Yang, Samuel W Teitelbaum, Gilberto De La Pena, Takahiro Sato, Matthieu Chollet, Diling Zhu, Jennifer Niedziela, Dipanshu Bansal, Andrew F May, Aaron M Lindenberg, Olivier Delaire, David A Reis, Mariano Trigo We use ultrafast X-ray scattering to study SnSe, a resonantly bonded material. Resonantly bonded materials have various functional properties directly associated with the |
Monday, March 6, 2023 5:24PM - 5:36PM |
D25.00011: Femtosecond orbital dynamics driving nonequilibrium melting transition revealed by ultrafast resonant X-ray scattering Heemin Lee, Je Young Ahn, Sae Hwan Chun, Do Hyung Cho, Daeho Sung, Chulho Jung, Jaeyong Shin, Junha Hwang, Sung Soo Ha, Hoyoung Jang, Byeong-Gwan Cho, Sunam Kim, Jaeku Park, Daewoong Nam, Intae Eom, Tae Yeong Koo, Ji Hoon Shim, Do Young Noh, Changyong Song Photo-induced nonequilibrium phase transitions stimulate the interest on dynamic interactions between electrons and crystalline ions, which has been largely overlooked within Born-Oppenheimer adiabatic approximations. Ultrafast melting before lattice thermalization prompts researchers to revisit this issue to propose physical models accounting for the instantaneous weakening of the crystal bonding from photo-excited electrons. However, the absence of direct evidence manifesting the role of orbital dynamics in lattice disorder leaves this interpretation speculative. In this study, by performing time-resolved resonant X-ray scattering with an X-ray free-electron laser, we directly monitored ultrafast dynamics of bonding orbitals that drive the photo-induced melting transition. Increased laser fluence amplifies the orbital disturbance to expedite the lattice disorder approaching the sub-picosecond scale of the nonthermal regime. The lattice disorder time displays strong nonlinear dependence on the laser fluence reflecting cross-over behavior from thermal-driven to nonthermal-dominant regime, which is also verified by ab initio and two-temperature molecular dynamics simulations. This study elucidates the impact of bonding orbitals on lattice stability with unifying interpretation on photo-induced melting. |
Monday, March 6, 2023 5:36PM - 5:48PM |
D25.00012: Single-pulse diffraction imaging of ultrafast melting in gold nanorod Eunyoung Park, Junha Hwang, Jaeyong Shin, Sung Yun Lee, Heemin Lee, Seung Phil Heo, Daewoong Nam, Sangsoo Kim, Min Seok Kim, In Tae Eom, Do Young Noh, Changyong Song Ultrafast light–matter interaction invigorates research activities on light induced quantum control of materials properties by providing routes to explore new phases of matters in nonequilibrium states. With the exclusive excitations of electrons through femtosecond IR laser pulses, various physical processes can be accessed mode selectively, which enables the way to tackle fundamental science issues including the role of electrons in driving crystal phase changes. Au nanorod, are elongated gold single nanoparticle that has longitudinal localized surface plasmon resonance (LSPR). Understanding this surface plasmons in Au nanorod is essential, which enables to control optical properties in metal nanostructures. Despite the significance of surface plasmons in the light-matter interaction in metallic nanoparticles, the role of the localized surface plasmon resonance in ultrafast melting has remained elusive. We studied the impact of surface plasmons dynamics in ultrafast phase transition of Au nanoparticle using femtosecond pump-probe X-ray imaging at PAL-XFEL. To study further, we directly imaged the reaction dynamics of photoinduced Au nanorod with femtosecond X-ray pulses. Shape distortion caused by LSPR and further investigation of laser fluence and polarization direction dependence was carried out to result in various melting reaction in reaction in response to the surface plasmon excitations in metallic nanoparticles. |
Monday, March 6, 2023 5:48PM - 6:00PM |
D25.00013: Ultrafast magnetic and charge dynamics in confined NdNiO3 superlattices Ankit S Disa The rare-earth nickelates (RNiO3) provide a model system for studying correlated electronic phenomena due to the existence of multiple forms of coupled electronic, magnetic, and structural order. NdNiO3 is a unique member of the family in which the paramagnetic-antiferromagnetic, metal-insulator, and charge ordering phase transitions all coincide in the bulk. When confined in NdNiO3/NdAlO3 superlattices, however, it was shown that these phase transitions split and the electronic ground state modified due to the influence of interfacial coupling and dimensionality. Here, we study the ultrafast electronic and magnetic dynamics in such superlattices upon photoexcitation using time-resolved resonant soft x-ray scattering and absorption spectroscopy. We observe the photo-induced melting of long-range antiferromagnetic order for different NdNiO3 layer thicknesses, finding an enhanced magnetic stiffness in the thinnest layers relative to the bulk. We further compare the magnetic order parameter with measured changes in the Ni d orbital configuration on picosecond time scales to elucidate the impact of interfacial electronic reconstructions on the optically driven phase transition. This work demonstrates that atomically engineered heterostructures provide a general pathway to control non-equilibrium phases and dynamics in correlated systems. |
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