Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session M50: Non-Equilibrium Dynamics |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Alexander Kemper, North Carolina State University Room: Mile High Ballroom 1C |
Wednesday, March 4, 2020 11:15AM - 11:27AM |
M50.00001: Ultrafast magnetic dynamics in insulating YBa2Cu3O6+x revealed by time resolved two-magnon Raman Scattering. Dmitry Reznik, Jhih-An Yang, Nick Pellatz, Thomas Wolf Measurement and control of magnetic order and correlations in real time is a rapidly developing scientific area relevant for magnetic memory and spintronics. In these experiments an ultrashort laser pulse (pump) is first absorbed by excitations carrying electric dipole moment. These then give their energy to the magnetic subsystem monitored by a time-resolved probe. A lot of progress has been made in investigations of ferromagnets but antiferromagnets are more challenging. Here we introduce time-resolved two-magnon Raman scattering as a novel real time probe of magnetic correlations especially well-suited for antiferromagnets. Its application to antiferromagnetic charge transfer insulator YBa2Cu3O6+x revealed rapid demagnetization within 90fs of photoexcitation. The relaxation back to thermal equilibrium is characterized by much slower timescales. One of these, which is extremely slow, indicates a novel metastable state hosting trapped charge carriers. |
Wednesday, March 4, 2020 11:27AM - 11:39AM |
M50.00002: Ultrafast charge dynamics in bulk alpha-Fe2O3 Naseem Ud Din, Volodymyr Turkowski, Hung-Tzu Chang, Alexander Guggenmos, Michael Zuerch, Stephen R. Leone, Talat S. Rahman Details of the ultrafast charge dynamics in oxides is crucial for interpretation of recent experimental data and for potential application of such materials in modern technologies. In this talk, we present results for ultrafast charge dynamics in laser pulse-excited antiferromagnet alpha-Fe2O3 obtained with the combined time-dependent density-functional theory and dynamical mean-field theory approach. In particular, we have calculated the time-resolved occupancies of the involved O(p) valence and Fe(d) conduction orbitals and demonstrated that due to strong electron-electron correlations there is delay of a few femtosecond in the charge accumulation in the electron and hole Fe(d) orbitals as compared to the O(p) hole orbitals. The obtained results for the ultrafast dynamics helps explain the attosecond transient absorption spectroscopy data for alpha-Fe2O3 which demonstrate ultrafast modification of the absorption spectra due to ligand-to-metal charge transfer. Our approach can be further extended to treat the femtosecond- and sub-femtosecond resolved dynamics of photoexcitation in strongly correlated materials, specifically, photo-induced insulator-to-metal transitions |
Wednesday, March 4, 2020 11:39AM - 11:51AM |
M50.00003: Non-equilibrium dynamics of vibrationally coupled electrons excited by coherent radiation John Sous, Benedikt Kloss, Dante Kennes, David Reichman, Andrew Millis The non-equilibrium dynamics of matter induced by coupling to light fields have made it possible to induce electronic phases of matter that may not exist at equilibrium, and which can be probed by optical and time-resolved spectroscopy. Transient superconductivity induced in atomic solids as a result of enhancement of atomic vibrations excited by light presents one exciting avenue. Here we employ tensor network methods to simulate the dynamics of a metal driven to a highly excited state at initial time by a pump that excites specific vibrational modes. We study the evolution with time of electronic and vibrational observables and observe non-trivial dynamics of density wave and superconducting correlations. |
Wednesday, March 4, 2020 11:51AM - 12:03PM |
M50.00004: High Harmonic Generation and Nonequilibrium Quasiparticle Dynamics in an Unconventional Superconductor with Competing Order Jian-Xin Zhu, Benedikt Fauseweh, Wei Zhu, Chen-Yen Lai A common feature of unconventional superconductors, ranging from high-temperature cuprate, heavy fermion, and recently discovered iron-based compounds, is the close proximity of unconventional superconductivity to an antiferromagnetic phase. The interplay of the unconventional superconductivity with the competing order remains an interesting scientific question. Recently, the ultrafast laser pulse pump-probe technique has become a powerful approach to uncover novel phases and associated quasiparticles dynamics in strongly correlated electron systems. Here we study an effective t-t’-U-V Hubbard model which captures the competition between antiferromagnetic spin-density wave (SDW) and d-wave superconducting (DSC) orderings. We show that an ultrafast electromagnetic field can drive the two competing order parameters uniquely depending on different regimes of hole doping. We further elucidate the consequence of the photoinduced electronic states by calculating the high harmonic generation and nonequilibrium momentum-dependent single-particle spectral function. |
Wednesday, March 4, 2020 12:03PM - 12:15PM |
M50.00005: Characterization of photoexcited states in the half-filled one-dimensional extended Hubbard model assisted by machine learning Kazuya Shinjo, Shigetoshi Sota, Seiji Yunoki, Takami Tohyama Photoinduced nonequilibrium states can provide new insight into dynamical properties of strongly correlated electron systems. One of the typical and extensively studied systems is the half-filled one-dimensional extended Hubbard model (1DEHM). Here, we propose that the supervised machine learning (ML) can provide useful information for characterizing photoexcited states in 1DEHM [1]. Using entanglement spectra as a training dataset, we construct a neural network. Judging from the trained network, we find that bond-spin-density wave (BSDW) order can be enhanced in photoexcited states if the frequency of a driving pulse nearly resonates with a gap. We separately calculate the time evolution of local and non-local order parameters and confirm that the correlation functions of BSDW are enhanced by photoexcitation as predicted by ML. Predicting BSDW demonstrates the advantage of ML to assist characterizing photoexcited quantum states. |
Wednesday, March 4, 2020 12:15PM - 12:27PM |
M50.00006: Negative absolute conductivity in photoexcited metals Giuliano Chiriaco, Andrew Millis, Igor L Aleiner We show that in a model of a metal photoexcited by a pump pulse resonant with a phonon mode, the absolute dc conductivity may become transiently negative, depending on the interplay between the electronic structure, the phonon frequency and the pump intensity. The analysis includes the effects of inelastic scattering and thermal relaxation. Results for the time evolution of the negative conductivity state are presented, showing that the associated non-equilibrium physics may persist for long times after the pulse. Our findings provide a theoretical justification for previously proposed phenomenology and indicate new routes to the generation and exploration of intrinsically non-equilibrium states. |
Wednesday, March 4, 2020 12:27PM - 12:39PM |
M50.00007: Matrix product state investigations of time-dependent spectral functions after a photoexcitation Constantin Meyer, Salvatore Manmana We study the time-dependent dynamical structure factor after a photoexcitation of a variant of the 1d Hubbard model with a background staggered magnetic field using matrix product state (MPS) techniques. In particular, we use the time-dependent variational principle (TDVP) to investigate the time evolution of the band population, which is a quantity accessible to time-resolved ARPES experiments. Different scenarios for the photoexcitations are discussed, e.g., Peierls-substitution or direct excitation in k-space. Using MPS, we can study in detail the effect of the electron-electron interaction on the redistribution of the band populations in the various photoexcitation setups. An outlook to the relevance of electron-electron interactions on light-harvesting mechanisms in correlated materials is given. |
Wednesday, March 4, 2020 12:39PM - 12:51PM |
M50.00008: Field-Driven Correlated Quantum Systems, Bridging the Gap Between the Transient and the Steady State Eric Dohner, Herbert Fotso, Alexander F Kemper, James Freericks Correlated quantum systems away from equilibrium have rightfully generated a lot of interest. Computational methods play an important role in understanding these systems but they are constrained by difficulties inherent to correlated systems that are exacerbated away from equilibrium. This prevents a full characterization of the dynamics. Previously, a set of relaxation scenarios were identified when systems initially in equilibrium are suddenly driven by a DC electric field. In particular, for certain parameters both the Hubbard and the Falicov-Kimball models evolve monotonically towards infinite temperature steady states that can be fully characterized by formulating solutions directly in the steady state. In the process these systems evolve through successive quasi-thermal states obeying the fluctuation dissipation theorem. We demonstrate an extrapolation scheme that can be leveraged to extend the characterization of the system from equilibrium to steady state at minimal computational cost. Namely, we extrapolate the monotonic temperature of the system and use the fluctuation dissipation theorem to construct the self-energy beyond the transient. All momentum dependent quantities can then be obtained within the DMFT formalism. |
Wednesday, March 4, 2020 12:51PM - 1:03PM |
M50.00009: Photon echo in the Coloumb glass phase as observed with 2D non-linear THz spectroscopy Fahad Mahmood, Dipanjan Chaudhuri, David Barbalas, Rahul Nandkishore, Peter Armitage Phosphorous doped Silicon (P:Si) near the metal insulator transition (MIT) hosts a Coulomb glass phase where charge carriers are localized and have strong long-range Coulomb interactions. Here we perform 2D non-linear THz spectroscopy to study the low energy non-linear electrodynamics of charge carriers in the Coulomb phase. Two time-delayed THz pulses with field strengths on the order of 100 kV/cm are applied sequentially on the sample to extract a 2D spectrum of the non-linear susceptibility of the sample as a function of emission and absorption frequencies. Distinct third-order nonlinear signals are identified in the 2D spectra including a photon echo, the anti-diagonal linewidth of which is used to determine the decoherence time (T2) of excited carriers. This is compared with the energy relaxation time (T1) to understand the interplay between site disorder and long-range interactions as the MIT is approached. |
Wednesday, March 4, 2020 1:03PM - 1:15PM |
M50.00010: The quadratically driven nonlinear photonic lattice and its dissipative phase transition: from quantum to classical Wouter Verstraelen, Riccardo Rota, Vincenzo Savona, Michiel Wouters Phase transitions (PT) appear in many flavors. In a Classical PT it results from a competition between energy and entropy, whereas in a quantum PT at zero temperature it results from the competition between non-commuting terms in the Hamiltonian. A quantum PT at finite temperature either vanishes or exhibits a continuous crossover to a classical PT [1]. The fate of a quantum PT at finite dissipation is much less understood. |
Wednesday, March 4, 2020 1:15PM - 1:27PM |
M50.00011: Accessing quantum phases in Hubbard honeycomb lattice using an electromagnetic drive Umesh Kumar, Shizeng Lin In the recent past, there has been a great interest in creating novel states of matter under driven conditions, in the condensed matter physics. The Hubbard honeycomb lattice is known to host rich phases [1]. The presence of a periodic drive such as an electromagnetic field in the lattice can be used to tune parameters and to generate new interactions, which can stabilize novel quantum states that is absent in equilibrium. Using Schrieffer-Wolff transformation for the periodically driven system [2] and high-frequency approximation on the drive, we evaluate an effective low-energy Hamiltonian for the Hubbard honeycomb lattice in the presence of drive. We estimate the conditions on the electromagnetic drive that can allow one to tune to different quantum phases, such as transient superconductivity in our model. |
Wednesday, March 4, 2020 1:27PM - 1:39PM |
M50.00012: Long-lived coherent states in photo-excited NiO Denis Golez, Konrad Gillmeister, Nikolaj Bittner, Yaroslav Pavlyukh, Cheng-Tien Chiang, Philipp Werner, Wolf Widdra Charge excitations across electronic band gaps are a key ingredient for transport in optoelectronics and light harvesting applications. In contrast to conventional semiconductors, studies of above-band-gap photoexcitations in strongly correlated materials are still in their infancy. |
Wednesday, March 4, 2020 1:39PM - 1:51PM |
M50.00013: Creation of Nonthermal Excited State Populations in a Large U Mott Insulator Daniel Nevola, Alexander W Bataller, Ankit Kumar, Samanvitha Sridhar, Jordan Frick, Shaun O'Donnell, Harald W Ade, Paul Maggard, Alexander F Kemper, Kenan Gundogdu, Daniel Dougherty The ability to tune between thermal and nonthermal populations lies at the heart at the heart of quantum control on ultrafast timescales. In this work, we perform time-and-angle resolved spectroscopy on the spin-orbit assisted Mott insulator α-RuCl3. We demonstrate the ability to tune between thermalized and nonthermalized populations in the upper Hubbard band by tuning the pump energy. These populations are also shown to thermalize and decay on timescales much faster than those predicted by theory. |
Wednesday, March 4, 2020 1:51PM - 2:03PM |
M50.00014: Laser pulse driven nonequilibrium dynamics in the Kondo lattice model Benedikt Fauseweh, Jian-Xin Zhu Experimental advances in nonlinear optics and ultrafast spectroscopy allow for unprecedented access to nonequilibrium physics of strongly correlated materials. By using this approach, many new and exciting phenomena have been discovered in recent years. They include light-induced superconductivity, the generation of Higgs oscillations, and the dynamical coupling of ferroelectric and ferromagnetic order. Heavy fermion systems are one prototypical class of strongly correlated materials. The interplay between localized magnetic moments and conduction electrons are the driver behind unconventional superconductivity and quantum criticality. The Kondo lattice model is used to describe the emergent phenomena of such systems. By using the powerful time-dependent variational Monte Carlo method, we investigate the nonequilibrium dynamics of the model after strong laser excitation. We demonstrate that the spin and charge fluctuations can be manipulated by varying shape and intensity of the laser pulse in different regimes of electron filling factor. In addition, experimentally measurable quantities are calculated to manifest the dynamics. |
Wednesday, March 4, 2020 2:03PM - 2:15PM |
M50.00015: Out-of-equilibrium dynamics in a 2D electron system with screened Coulomb interactions Lily Stanley, Dragana Popovic Considerable experimental evidence suggests that Coulomb interactions are responsible for a variety of phenomena observed in the metallic regime of 2D systems, as well as for glassy behavior near the 2D metal-insulator transition (MIT) and in the insulating regime. To address the fundamental question whether glassy behavior of electrons exists in the absence of long-range Coulomb interactions, we report a study of conductivity relaxations after excitation out of equilibrium, in particular after applying a large change of carrier density ns, over a wide range of temperatures and ns, spanning the 2D MIT. Experiments were performed on strongly disordered thin-oxide Si MOSFETs in which the Coulomb interaction is screened by the nearby metallic gate. The results show differences in the dynamics compared to the case of long-range interactions, and suggest the key role of long-range Coulomb interactions in the existence of glassy behavior of electrons near the 2D MIT in strongly disordered samples. |
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