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 N38: Light Induced Structural Control of Electronic Phases IIIFocus
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Sponsoring Units: DMP Chair: Ankit Disa, Cornell University Room: Room 230 |
Wednesday, March 8, 2023 11:30AM - 12:06PM |
N38.00001: Quantum spectroscopies for quantum materials Invited Speaker: Daniele Fausti The rich phase diagrams of many transition metal oxides (TMOs) is the result of the intricate interplay between electrons, phonons, and magnons. This makes TMOs very susceptible to external parameters such as pressure, doping, magnetic field, and temperature which in turn can be used to finely tune their properties. The same susceptibility makes TMOs the ideal playground to design experiments where the interaction between tailored electromagnetic fields and matter can trigger the onset of new, sometimes exotic, physical properties. This aspect has been explored in time domain studies [1] and has led to the demonstration that ultrashort mid-IR light pulses can “force” the formation of quantum coherent states in matter, disclosing a new regime of physics where thermodynamic limits may be bridged and quantum effects can, in principle, appear at ambient temperatures. |
Wednesday, March 8, 2023 12:06PM - 12:18PM |
N38.00002: ULTRAFAST MID-INFRARED PUMP-OPTICAL PROBE SPECTROSCOPY OF INSLULATING La2CuO4 Mustafa G Ali, Kelson Kaj, Varun Ramaprasad, Eli Zohglin, Steven J Gomez, Stephen D Wilson, Richard D Averitt We report some further progress on the excitation of coherent longitudinal acoustic phonons (CLAPs) in the Mott insulator La2CuO4 using intense ultrafast mid-infrared laser pulses measured by changes in the reflectivity (at 800 nm) as a function of pump-probe delay. This talk seeks to motivate the possible mechanisms that enable and resolve a below gap CLAP excitation. More generally, we also look toward implementing this coherent population of longitudinal acoustic phonons - a strain wave - as a reporter of low energy dynamics in quantum materials. |
Wednesday, March 8, 2023 12:18PM - 12:30PM |
N38.00003: Multidimensional Phononics in YBa2Cu3O6+x Niloofar Taherian In underdoped YBa2Cu3O6+x superconductors, resonant photo-excitation of the apical oxygen phonon modes at mid-infared frequencies gives rise to transient features in the terahertz reflectivity that indicate nonequilibrium superconductivity well above the critical temperature and up to the pseudogap temperature. |
Wednesday, March 8, 2023 12:30PM - 12:42PM |
N38.00004: Light induced symmetry change in Cr2O3 by time resolved second harmonic generation Xinshu Zhang The development of ultrafast lasers has offered an alternative way to alter the properties of materials in addition to conventional stimulus. In this work, we study anti-ferromagnetic Cr2O3, which is known as a typical magnetoelectric, with time resolved second harmonic generation (SHG). We are able to change the symmetry of Cr2O3 transiently with a near infrared pump below the electronic gap. The symmetry changes are monitored by rotational anisotropy SHG. Our work demonstrates an effective way to manipulate the properties of materials on ultrafast time scales. |
Wednesday, March 8, 2023 12:42PM - 12:54PM |
N38.00005: Electron-hole Liquid in Direct Bandgap Semiconductor at Room Temperature Ajay K Poonia, Pushpendra Yadav, Barnali Mondal, Angshuman Nag Nag, Amit Agarwal, Adarsh K V The condensation of charge carriers in semiconductors known as electron-hole liquid (EHL) represents a macroscopic quantum state of matter, where a bunch of correlated particles form the tiny droplets that behave as a collective state of a single entity. Due to primary obstacles of excess thermal energy, short carrier lifetime, and low binding energy, EHL is realized only under extreme conditions, like cryogenic temperature and in materials having multivalley indirect band-structure, restricting their potential applications. Here we present our results of the first observation of EHL in the direct bandgap metal halide perovskite nanocrystals at ambient temperature. In our measurements the polarization resolved transient absorption technique employed to investigate the EHL state, where the opposite circularly polarized light pulses reveal the ground state of EHL below the exciton and biexciton states. Further EHL’s condensation and evaporation processes are monitored by excited state absorption of the droplets. By theoretical calculation critical temperature of 386 K and critical density of 8×1018 cm-3 is estimated. Our study will pave the way for the development of quantum phenomena-based technologies and provide a new platform to understand the many-body correlated effect of quantum materials. |
Wednesday, March 8, 2023 12:54PM - 1:06PM |
N38.00006: Photoinduced Chemical Potential shift in Topological Material Tika R Kafle, Yingchao Zhang, Xun Shi, Wenjing You, Na Li, Qing-Xing Dong, Gen-Fu Chen, Kai Rossnagel, Henry C Kapteyn, Margaret M Murnane Topological crystalline insulators (TCI) are new class of quantum materials with an even number of Dirac surface states protected by crystal symmetry. External excitation via pressure, magnetic field and physical doping can be applied to break the symmetry of such materials and hence tune their electronic properties. Using time and angle resolved photoemission spectroscopy, we report the observation of a shift in the chemical potential of NaCd4As3, a mirror symmetry protected TCI. This material exhibits a topological phase transition below 200 K from a TCI to a topological insulator (TI), resulting from the breaking of the mirror symmetry due to a structural phase transition. Within 500 fs of the laser excitation pulse, a change in chemical potential of 170 meV is observed before it gradually relaxes to the ground state after 6 ps. This shift results from an asymmetric distribution of charge carriers induced by the femtosecond laser within sensitive electron bands near the Fermi level. Our results show that ultrafast light pulses can tune the electronic properties of phase-rich topological materials while keeping their intrinsic properties intact. |
Wednesday, March 8, 2023 1:06PM - 1:18PM |
N38.00007: Spin-orbit mixed states in an electromagnetic field Gervasi Herranz, Alejandro S Miñarro, Ernest Pastor, Jayagreav Kannan, Allan S Johnson, Blai Casals Motivated by our recent discovery of large gyrotropic signals in some Jahn-Teller manganites [1], we explore the interaction of light with spin-mixed states in 3d metals. We show that spin-orbit mixing enables electronic transitions that are sensitive to circularly polarized light, giving rise to a gyrotropic response. Such interactions offer the opportunity to use light to entangle orbital and spin degrees of freedom. We find that, in addition to spin-orbit coupling, Jahn-Teller interactions are relevant to enhance the observed optical gyrotropy in solid-state 3d systems. Our approach, which includes a group-theoretic treatment of spin-orbit coupling, has wide applicability and provides a versatile tool to explore the interaction of electromagnetic fields with electronic states in transition metals with arbitrary spin-orbit coupling strength and point-group symmetries [2]. Ultrafast pump-probe experiments further confirm that the optical properties of the Janh-Teller manganites can be described completely in terms of a two polaron mode model, and allow us to extract the lifetime of the excitations and the role of oxygen mediated inter-site hopping. |
Wednesday, March 8, 2023 1:18PM - 1:30PM |
N38.00008: Witnessing Light-Driven Entanglement using Time-Resolved Resonant Inelastic X-Ray Scattering Jordyn Hales Quantum computing takes advantage of principles of quantum mechanics, specifically entanglement, to encode information, which in turn requires characterizing and controlling entanglement within these materials. However, defining a figure of merit for entanglement within a material is both theoretically and experimentally challenging. At equilibrium, extracting entanglement witnesses from spectroscopies is feasible, but this approach cannot be directly extended out of equilibrium and is incompatible with laser control of materials. Here, we propose a systematic approach to quantify the time-dependent entanglement of transient states of quantum materials through time-resolved resonant inelastic x-ray scattering(trRIXS). We demonstrate the efficiency of our approach using a quarter-filled extended Hubbard model(EHM), and predict light-enhanced quantum entanglement that we attribute to the proximity to a phase boundary. This work sets the stage for experimentally witnessing and controlling entanglement in light-driven quantum materials via solid-state accessible ultrafast spectroscopic measurements. |
Wednesday, March 8, 2023 1:30PM - 1:42PM |
N38.00009: Critical light-matter entanglement at cavity mediated phase transition Giuliano Chiriaco, Marcello Dalmonte, Titas Chanda We consider a model of a light-matter system, in which a system of fermions (or bosons) is coupled to a photonic mode that drives a phase transitions in the matter degrees of freedom. Starting from a simplified analytical model, we show that the entanglement between light and matter vanishes at small and large coupling strength, and shows a peak in the proximity of the transition. We perform numerical simulations for a specific model (relevant to both solid state and cold atom platforms), and show that the entanglement displays critical behavior at the transition, and features maximum susceptibility, as demonstrated by a maximal entanglement capacity. Remarkably, light-matter entanglement provides direct access to critical exponents, suggesting a novel approach to measure universal properties without direct matter probes. |
Wednesday, March 8, 2023 1:42PM - 1:54PM |
N38.00010: Controlling the magnetic state of the proximate quantum spin liquid α-RuCl3 with an optical cavity Emil Vinas Boström, Angel Rubio Harnessing the enhanced light-matter coupling arising from mode volume compression in optical cavities is a promising route towards functionalizing quantum materials and realizing exotic states of matter. Here, we extend material engineering via cavity quantum electrodynamics fluctuations to magnetic systems, by demonstrating that a Fabry-Pérot cavity can be used to control the magnetic state of the proximate spin liquid α-RuCl3. Depending on specific cavity properties such as the frequency, photon occupation, and strength of the light-matter coupling, any of the magnetic phases supported by the extended Kitaev model can be stabilized. In particular, in the THz regime, we show that the cavity vacuum fluctuations alone are sufficient to bring α-RuCl3 from a zigzag antiferromagnetic to a ferromagnetic state. |
Wednesday, March 8, 2023 1:54PM - 2:06PM |
N38.00011: Cavity-renormalized quantum criticality in a honeycomb bilayer antiferromagnet Lukas Weber, Emil Vi, Martin Claassen, Angel Rubio, Dante M Kennes We investigate the fate of a quantum critical dimerized antiferromagnet when it is coupled to a quantized high-frequency cavity field. Using unbiased Quantum Monte Carlo simulations, we compute the scaling behavior of the magnetic structure factor and other observables. While the position and universality class are not changed by a single cavity mode, the critical fluctuations themselves obtain a sizable enhancement, scaling with a fractional exponent that defies expectations based on simple perturbation theory. The scaling exponent can be understood using a generic scaling argument, based on which we predict that the effect may be even stronger in other universality classes. |
Wednesday, March 8, 2023 2:06PM - 2:18PM |
N38.00012: Strong light-matter coupling for band electrons Christian J Eckhardt, Giacomo Passetti, Marios H Michael, Michael A Sentef, Dante M Kennes Hybridizing light and matter degrees of freedom by means of cavities can be used to control quantum materials. In the case of band electrons, we show that quantum fluctuations play a pivotal role for such light-matter hybridization. We discuss the potential of different platforms such as Fabry-Perot cavities and surface plasmon polaritons (SPPs) to control material properties. |
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