Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 65, Number 4
Monday–Friday, June 1–5, 2020; Portland, Oregon
Session N05: FOCUS: Ultrafast Processes in SolidsFocus Live
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Sponsoring Units: DCMP Chair: Alexandra Landsman, Ohio State University Room: D139-140 |
Thursday, June 4, 2020 10:30AM - 11:00AM Live |
N05.00001: \textbf{Using light to control electrons to create new light}. Invited Speaker: Paul Corkum Intense Gaussian light can create an electron-hole pair in a semiconductor (or dielectric) and guide the relative electron-hole trajectory. Before dephasing, in semiconductors (and some dielectrics), the electron and hole have a significant chance of re-encountering each other where they can re-combine, creating a sub-cycle optical burst of coherent, short-wavelength radiation. Repeated over many cycles, we produce high harmonic radiation stretching into the VUV. We use in-situ measurement to confirm that the process I have just described is valid (and very similar to what occurs in gases). One notable distinction is that the absorption length of VUV light in solids is very short, thereby weakening the influence of phase matching. However, I will show that phase matching still plays a role [1]. What I have described above happens locally, everywhere across the beam profile, but by using vector beams, light control over electrons and holes can also be at the whole beam level, especially when combined with coherent control (using a beam and its second harmonic). I will show that we can drive directed currents even with relatively low intensity light. Surprisingly, all we need is two pathway interference to drive currents with 360 degree control pixel-by-pixel with only the relative phase between a circularly polarized beam and linear polarized second harmonic as a variable. One important application is to generate THz solenoidal magnetic field transients. I will show that we create ring currents in GaAs with an associated magnetic field [2]. We predict very large ring currents and very large magnetic field transients in breakdown gases [3]. [1] A. Korobenko, et al., \textit{Opt Express}. \textbf{27}, 32630 (2019). [2] S. Sederberg, F. Kong, F. Hufnagel, E. Karimi, C. Zhang, P. B. Corkum, unpublished results. [3] S. Sederberg, F. Kong, P. B. Corkum,$^{\mathrm{\thinspace }}$unpublished results. [Preview Abstract] |
Thursday, June 4, 2020 11:00AM - 11:30AM Live |
N05.00002: Imperfect recollisions in HHG in solids: real space vs reciprocal space pictures Invited Speaker: Mette Gaarde The dynamical process that leads to the generation of high order harmonics in solids can be described in either real space or reciprocal (k) space. In both pictures, the process starts by an electron tunneling from the valence to the conduction band and is followed by acceleration by the strong field. In k-space, the resulting dynamics is described in terms of the electron moving on the conduction band, which leads to intra- and interband emission processes. In real space, one can think of laser-driven oscillations of highly delocalized electron and hole wave packets, extending over many unit cells of the lattice, which leads to emission of (interband) harmonics when the electron and hole reencounter each other in space. Using the two-dimensional hexagonal boron nitride (h-BN) system as an example, I will discuss how the delocalized nature of the quantum wave packet means that even imperfect recollisions -- when the center of the electron and hole wave packets do not exactly overlap -- contribute significantly to the harmonic emission. Imperfect recollisions arise naturally in systems with non-zero Berry curvatures, or any system driven by elliptically polarized laser pulses, and should thus be taken into account when interpreting experimental spectra. [Preview Abstract] |
Thursday, June 4, 2020 11:30AM - 11:42AM Live |
N05.00003: Extraction of higher-order nonlinear electronic response in solids using high harmonic generation Lisa Ortmann, S. Han, H. Kim, Y. Kim, T. Oka, A. Chacon, B. Doran, M. Ciappina, M. Lewenstein, S.-W. Kim, S. Kim, A. S. Landsman Nonlinear susceptibilities are key to ultrafast lightwave driven optoelectronics, allowing petahertz scaling manipulation of the signal. Recent experiments\footnote{A. Sommer et al., Nature \textbf{534}, 86–90 (2016).} retrieved a 3rd order nonlinear susceptibility by comparing the nonlinear response induced by a strong laser field to a linear response induced by the otherwise identical weak field. The highly nonlinear nature of high harmonic generation has the potential to extract even higher order nonlinear susceptibility terms. However, up till now, such characterization has been elusive due to a lack of direct correspondence between high harmonics and nonlinear susceptibilities. We demonstrate\footnote{S. Han, L. Ortmann, H. Kim et al., Nat. Comm. \textbf{10}, 3272 (2019).} a regime where such correspondence can be clearly made, extracting nonlinear susceptibilities from sapphire of the same order as the measured high harmonics. The extracted high order susceptibilities show angular-resolved periodicities arising from variation in the band structure with crystal orientation. Our results open a door to multi-channel signal processing, controlled by laser polarization. [Preview Abstract] |
Thursday, June 4, 2020 11:42AM - 11:54AM Live |
N05.00004: High Harmonic Generation (HHG) in solids Francisco Navarrete, Marcelo Ciappina, Uwe Thumm Over the last decade much progress has been made in detecting, modeling, and analyzing HHG in solids, yet even some of the most prominent features in solid HHG spectra remain poorly understood [1-5]. We present a detailed analysis of the intra- and interband HH emission, based on HH spectra calculated numerically by solving the time-dependent Schr\”odinger equation in single-active-electron approximation within an adiabatic basis-set expansion including the entire first Brillouin Zone (BZ). We analyze contributions to inter- and intraband HH emission from different crystal-momentum channels and compare fully numerical calculations with semiclassical approximations for a large range of driving-laser-pulse intensities and numbers of included conduction bands. In addition, we discuss the dependence of solid HHG on the pulse-shape for driving two-color pulses [4] and on impurity-doping [5]. [1] S. Ghimire et al., Nat. Phys, 7, 138 (2011). [2] G. Vampa, et al., Phys. Rev. Lett, 113, 073901 (2014). [3] F. Navarrete, et al., Phys. Rev. A 100, 033405 (2019) [4] T. T. Luu and H. J. Wörner Phys. Rev. A 98, 041802(R) (2018). [5] V. E. Nefedova et al., arXiv:2001.00839 [Preview Abstract] |
Thursday, June 4, 2020 11:54AM - 12:06PM Live |
N05.00005: High-harmonic spectroscopy of quantum materials Denitsa Baykusheva, Alexis Chacon, Jian Lu, Trevor Bailey, Jonathan Sobota, Hadas Soifer, Patrick Kirchmann, Costel Rotundu, Ctirad Uher, Tony Heinz, David Reis, Shambhu Ghimire We report the evidence of generation of high-order harmonics from the surface states of a three-dimensional topological insulator, Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$, subject to strong mid-infrared laser fields. The response from the surface is identified by analyzing the polarization of high-harmonics and by exploiting the fact that inversion symmetry is broken at the surface. In experiments, high-order harmonics up to 17$^{\mathrm{th}}$ order are observed without sample damage at the peak intensity of approx. 3x10$^{\mathrm{10}}$ W/cm$^{\mathrm{2}}$. The non-trivial response of the topological material is seen to manifest itself through a significantly enhanced harmonic yield for circularly polarized driving laser fields. [Preview Abstract] |
Thursday, June 4, 2020 12:06PM - 12:18PM On Demand |
N05.00006: Terahertz Perturbed, Mid-infrared Driven High-Order Harmonic Generation from Solids Sha Li, Yaguo Tang, Zhou Wang, Kent Talbert, Yang Cheng, Fengyuan Yang, Pierre Agostini, Louis DiMauro We have studied high-order harmonic generation from ZnO thin film driven by an 80 fs, 3.6 $\mu $m mid-infrared (MIR) pulse, and dressed by a 2 ps, 600 $\mu $m single-cycle terahertz (THz) pulse. The existence of the weak quasi-DC THz field breaks the symmetry of the MIR driving field and/or the symmetry of the crystal, and we observe the generation of even-order harmonics, up to harmonic order 20. The intensity of each even-order harmonic scales linearly with that of the THz pulse, indicating a perturbation that involves one THz photon. We also find that, when the THz field is applied, the intensities of the odd-order harmonics are reduced (e.g., harmonic order 19, $I (F$THz $=$ 300 kV/cm) \quad $\approx $0.65$ * I (F$THz $=$ 0)), while the intensity of the total harmonics (odd $+$ even) stays constant, indicating that the alternation of the generalized electron-hole recollision by the THz field results in a repopulation of the total harmonics into each harmonic order. Our study paves the way for ultrafast control of the high harmonic generation process in solids by THz fields and suggests a novel method for THz metrology. [Preview Abstract] |
Thursday, June 4, 2020 12:18PM - 12:30PM Not Participating |
N05.00007: Super-resolution band structure reconstruction of monolayer tungsten diselenide Christoph Schmid, Leonard Weigl, Niklas Hofmann, Fabian Langer, Christoph Lange, Rupert Huber, Markus Borsch, Mackillo Kira Harnessing the carrier wave of an intense lightwave to drive the quantum motion of electrons in solids has set the stage for exciting strong-field phenomena, such as high-harmonic generation, dynamical Bloch oscillations, and interband quantum interference [1], as well as high-order sideband generation (HSG) [2,3]. Here, we demonstrate a novel concept for high-resolution band structure reconstruction by exploiting the band-selective transport in HSG. Varying the center frequency of the accelerating multi-terahertz wave over a full optical octave reveals a dramatic suppression of specific odd-order sidebands. A full quantum mechanical description of the underlying dynamics links this anomaly with specific resonances in the odd-order HSG emission. The explanation involves crystal-momentum combs that introduce super-resolution imaging capabilities in reciprocal space. This novel type of band structure spectroscopy paves the way towards a scalable all-optical strategy to map out key features of the electronic structure of a solid quantitatively. [1] M. Hohenleutner et al., Nature 523, 572-575 (2015). [2] F. Langer et al., Nature 533, 225-229 (2016). [3] F. Langer et al., Nature 557, 76-80 (2018). [Preview Abstract] |
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