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 X62: Ultrafast Dynamics and Control of Quantum MaterialsFocus Live
|
Hide Abstracts |
Sponsoring Units: DLS |
Friday, March 19, 2021 8:00AM - 8:36AM Live |
X62.00001: The order-disorder phase transition in VO2 revealed by an x-ray free electron laser Invited Speaker: Mariano Trigo Femtosecond laser pulses provide a promising strategy to control quantum phases of matter with potential to realize “properties on demand” [1]. While laser pulses can distort the lattice into novel structures with exotic properties not accessible in equilibrium, probing those transient structures remains a challenge. X-ray Free Electron Lasers (XFELs) hold promise to visualize the atomic and electronic structure of these transient states as they transform. I will present XFEL results on the ultrafast monoclinic (M 1 ) to rutile (R) transition of VO 2 . We used femtosecond x-ray diffuse scattering [2,3] at the Linac Coherent light Source (LCLS) at SLAC to study the structural dynamics of the transition at all length-scales. Contrary to the displacive transitions common among charge density waves (CDWs) where the dynamics occur in the vicinity of the CDW wavevector, the M 1 to R transformation in VO 2 proceeds by an ultrafast increase in the x-ray diffuse intensity spanning the Brillouin zone. The intensity momentum distribution shows that photoexcitation induces a prompt uncorrelated disordering of the vanadium dimers of the M 1 phase that reach a rutile quasi-equilibrium distribution in ~ 150 fs. Our results suggest that the pump induces a highly anharmonic potential that enables fast disordering of the lattice, which is intimately related with the high phonon entropy of the R phase. |
Friday, March 19, 2021 8:36AM - 9:12AM Not Participating |
X62.00002: Femtosecond Covariance Spectroscopy to Control Multimode Quantum Correlations Invited Speaker: Daniele Fausti The vast majority of nonlinear optical spectroscopies work in an integrated mode, namely they use the mean-value signal, properly averaged over several stroboscopic repetitions. While ensuring an adequate signal-to-noise ratio, this approach relies strongly on pulse-to-pulse consistency and has thus motivated significant efforts in pursuit of perfect experimental stability. By contrast, we have developed a fundamentally different approach, named Femtosecond Covariance Spectroscopy (FCS), which identifies noise as a powerful and unique asset to access information that standard mean-value experiments miss. FCS is based on covariance rather than mean-value observables and relies on the study of multimode quantum correlations imprinted on stochastic ultrashort pulses by light-matter interactions. As a proof of principle, we have successfully applied such approach to the study of Raman-active vibrational modes excited through Impulsive Stimulated Raman Scattering (ISRS) in crystalline quartz. Nevertheless, the impact of FCS is not only limited to the field of condensed matter physics. Indeed, given the formal analogy between the quantum description of ISRS and optomechanical experiments, FCS could pave the way to a new generation of experiments in which the coupling between the electromagnetic field and the mechanical oscillator, could be reproduced by the interaction between light pulses and phonon modes. |
Friday, March 19, 2021 9:12AM - 9:48AM Live |
X62.00003: Out-of-equilibrium phase competition mediated by photoinduced fluctuations Invited Speaker: Alfred Zong Engineering novel states of matter by an ultrafast laser pulse is at the forefront of materials research. One promising approach relies on systems that host competing ground states, where light suppresses the dominant order in equilibrium while strengthening the subdominant one. However, the interplay among competing orders remains difficult to study due to a lack of experimental probes that can measure intertwined dynamics all at once. In this talk, I will discuss a model charge-density-wave (CDW) family with two competing modulations, out of which only the dominant one appears in equilibrium. Using a pump-pump-probe scheme with ultrafast electron diffraction, we find that both CDW orders emerge simultaneously after photoexcitation. This joint growth lasts for a few picoseconds and features fluctuating patches of both density waves – in striking resemblance to the critical state near the equilibrium transition temperature. Our investigation unveils a codeveloping relation between an otherwise incompatible pair of CDWs in equilibrium. It further establishes photoinduced fluctuations as a generic pathway for realizing transient states in solids that possess competing phases. |
Friday, March 19, 2021 9:48AM - 10:24AM Live |
X62.00004: Local Symmetry Breaking and Spin Momentum Locking in Cuprates Superconductors Invited Speaker: Alessandra Lanzara The 20th century has been dominated by the realization that symmetry and symmetry breaking are keys to much of the novel phenomena observed in physics today. Superconductivity for example requires both time-reversal and inversion symmetry, and the removal of one of these (e.g. time reversal through a magnetic field) leads to the suppression of the superconducting order. Recently however it has been realized that, even if the global symmetry of the system is retained, a local symmetry breaking can still induce a variety of novel fascinating behaviors. |
Friday, March 19, 2021 10:24AM - 11:00AM Live |
X62.00005: Quantum Beats by Lightwave Acceleration of Broken-Symmetry Supercurrents Invited Speaker: JIGANG Wang Light-induced supercurrents chart a path forward for the electromagnetic design of emergent materials phases and collective modes for quantum engineering applications. In this talk, I will discuss our recent progress towards applying this new tuning knob, enabled by using single- and few-cycle THz pulses, to reveal some distinguishing features of quantum systems: Anderson pseudo-spin precessions and higher harmonics forbidden by equilibrium symmetry, hidden emergent phases that are difficult to be accessed by other tuning methods, Higgs modes in unconventional superconductors. We will also discuss how to extend THz light-driven coherence and subcycle symmetry breaking for quantum control of other complex systems including topological matter, with implications on quantum gate and sensing applications. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700