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 D30: Strongly Correlated Systems, Including Quantum Fluids and Solids II |
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Sponsoring Units: DCMP Chair: Eric Bauer, Los Alamos Natl Lab Room: Room 222/223 |
Monday, March 6, 2023 3:00PM - 3:12PM |
D30.00001: Tuning a coupled phase transition in nickelate thin films using helium ion implantation Rourav Basak, Sarmistha Das, Uday S Goteti, Brandon Gunn, Joshua Evans, Nirjhar Sarkar, Padraic Shafer, Christoph Klewe, John W Freeland, Fanny M Rodolakis, Shane A Cybart, Robert C Dynes, Alex Frano Coupling of lattice, charge and spin degrees of freedom in strongly correlated electron systems of rare earth nickelates leads to the concurrent first order phase transition from a paramagnetic metal to a bond-ordered antiferromagnetic insulator in NdNiO3 and PrNiO3. Identification of the driving electronic degree of freedom of this phase transition is still debated. Here we will show how increasing helium ion implantation to epitaxially grown films can act as a tuning knob to gradually suppress the phase transition. Then we will follow up with experimental results detailing the effect of helium ion implantation on individual electronic degrees of freedom. We will conclude our discussion with important insights on the coupled first order phase transition. |
Monday, March 6, 2023 3:12PM - 3:24PM |
D30.00002: Revisiting hydrogen doping in SmNiO3: A DFT+U and DMFT study Soumya S Bhat, Uthpala K Herath, Vijay Singh, Bilvin Varughese, Subramanian K Sankaranarayanan, Hyowon Park, Aldo H Romero Hydrogen-induced metal-to-insulator transition (MIT) in strongly correlated rare-earth nickelates has opened new directions to explore novel electronic and photonic devices. Although a significant understanding of doping-driven MIT exists, the quantification of doping concentration has remained unclear due to the difficulty in the characterization of hydrogen. Recent experimental work has realized a more significant hydrogen-induced enhancement in resistivity in SmNiO3 at lower doping concentration, in contrast to the previous understanding where a high doping concentration of 1 hydrogen per Ni atom (H : Ni = 1 : 1) was required to induce the insulating behavior. In the present work, we elucidate this by investigating the effect of various hydrogen doping concentrations on geometry and electronic structures using first-principles density functional theory (DFT)+U and dynamical mean-field theory (DMFT) calculations. We explore all possible H-interstitial configurations for 0.25, 0.5, 0.75, and 1 hydrogen per Ni in the SmNiO3 unit cell. Further, various H-migration paths are examined using nudged-elastic band calculations. Our findings demonstrate the significance of DMFT calculations to accurately describe the H-induced electronic phase transitions in strongly correlated materials. |
Monday, March 6, 2023 3:24PM - 3:36PM |
D30.00003: Momentum-selective opening of the Mott pseudogap indused by strong magnetic fluctuations Maria Chatzieleftheriou Two-dimensional electronic systems in the regime of strong electronic Coulomb correlations are particularly prone to non-local correlation effects not captured within dynamical mean field theory (DMFT). Here, we deploy a novel diagrammatic extension of DMFT, dubbed D-TRILEX, that allows one to account for non-local fluctuations. As expected, at high temperatures, where magnetic fluctuations are weak, non-local effects are small and the Mott transition is well described by DMFT. Upon lowering the temperature, however, the increasing magnetic fluctuations contribute to the formation of the Mott gap. We quantify their role in the Mott transition by studying the momentum-selective opening of the Mott pseudogap at the nodal and anti-nodal points. |
Monday, March 6, 2023 3:36PM - 3:48PM |
D30.00004: Strong electron-phonon coupling in Ta2Ni(Se,S)5 across the semimetal-semiconductor transition Cheng Chen, Weichen Tang, Xiang Chen, zhibo kang, Siqi Wang, Zhenglu Li, Jacob Ruff, Makoto Hashimoto, Donghui Lu, Christopher Jozwiak, Aaron Bostwick, Eli Rotenberg, Robert J Birgeneau, Yulin Chen, Steven G Louie, Yao Wang, Yu He During a band-gap tuned semimetal-to-semiconductor transition, the excitonic instability of the system, the spontaneous formation of electron-hole bound pairs via direct Coulomb attraction, often peaks when the bandgap crosses zero. However, such excitonic phase diagram can be altered in the presence of strong electron-phonon coupling. Here, via angle-resolved photoemission spectroscopy (ARPES) and high-resolution synchrotron x-ray diffraction (XRD), we report a monotonically suppressed broken-symmetry phase boundary across the semimetal-semiconductor transition in a leading excitonic insulator candidate system Ta2Ni(Se,S)5. Bolstered by first principles and model calculations, strong electron-phonon coupling is shown to substantially enhance the symmetry-breaking on the semimetal side, leading to negative electronic compressibility, pervasive lattice fluctuation, and a persistently gapped ground state. Our results not only resolve the longstanding debate about the nature of the intertwined order in Ta2NiSe5, but also lay the groundwork to a new solid-state platform for the investigation of excitonic instability amid electron-phonon solid coupling. |
Monday, March 6, 2023 3:48PM - 4:00PM |
D30.00005: Enhancement of Atomic Diffusion due to Electron Delocalization in Fluid Metals Chen Cheng, Gia-Wei Chern We present a general theory of atomic self-diffusion in the vicinity of a Mott metal-insulator transition in fluid metals. Starting from the Mott insulating phase, the delocalization of electrons gives rise to the emergence of attractive interatomic interaction, which, according to Einstein's relation, is expected to introduce an additional friction, hence reducing the atomic diffusivity. Yet, our quantum molecular dynamics simulations find an intriguing enhancement of the atomic diffusion facilitated by the emerging attractive forces. We demonstrate that this counterintuitive phenomenon results from a reduced effective repulsive core when the effect of the attractive tail is suppressed at high temperatures. The proposed scenario, which could account for diffusion enhancement in general simple liquids, is corroborated by the Chapman-Enskog theory and classical molecular dynamics simulations on an archetypal liquid model based on the Morse potential. Our work also sheds new lights on the nontrivial effects of electron correlation on atomic dynamics. |
Monday, March 6, 2023 4:00PM - 4:12PM |
D30.00006: Unusual electronic behavior at the interface of Iridate-Nickelate (5d-3d) heterostructures Sarmistha Das, Rourav Basak, Henry Navarro, IVAN K SCHULLER, Alex Frano The complex physics of transition metal oxides (TMOs)-based heterostructures with atomically sharp interfaces leads the way to unveil several novel functionalities which cannot be realized in the constituent bulk counterparts. The bi-layer thin films made of strongly correlated 3d PrNiO3 (PNO) and 5d SrIrO3 (SIO) with strong spin-orbit coupling (SOC), are indeed exceptionally fascinating in which the tuning of interface properties as a function of correlations/SOC strength of the constituents can be achieved. PNO exhibits a temperature-dependent phase transition from Antiferromagnetic (AFM) Insulator to Paramagnetic Semimetal and SIO possess a Paramagnetic Semimetal ground state. PNO is well known to exhibit physical properties depending on the oxygen stoichiometry. On the other hand, SIO has shown nontrivial quantum states through the Dzyaloshinskii−Moriya interaction associated with the strong SOC while being intercalated with other TMOs. Our high-quality PNO/SIO bilayers grown on SrTiO3 substrate exhibit very distinct electronic behavior upon the change of the layer stacking order. Additionally, with the controlled inclusion of oxygen vacancies, this contrasting behavior becomes even more prominent, and an unexpected metallicity sets down to 5K. Our X-ray absorption spectroscopy study further reveals that the unusual kind of charge-transfer phenomenon occurs at the 5d-3d interface. |
Monday, March 6, 2023 4:12PM - 4:24PM |
D30.00007: Multifractality Meets Entanglement: Relation for Non-Ergodic Extended States Giuseppe De Tomasi, Ivan M Khaymovich It is now well established that entanglement plays a central role on the thermalization process of quantum many-body systems. On the other hand, ergodicity is deeply connected to the notion of chaos, which also implies the equipartition of the wave function over the available many-body Fock states, which is usually quantified by multi-fractal analysis. |
Monday, March 6, 2023 4:24PM - 4:36PM |
D30.00008: Strongly correlated excitonic charge transfer insulators and selective Mott transition in twisted bilayers transition metal dichalcogenides (TMDs) Lorenzo Del Re In the last years, a novel class of materials, namely twisted layered heterostructures of transition metal dichalcogenides (TMDs), has emerged as a new experimental platform for the study of strongly correlated phases. Among other reasons, there is a great interest in TMDs because they are good candidates to host the so long sought excitonic insulating phase, that is stabilized by condensation of excitons, i.e. bound pairs of electrons and holes. The forbidden hybridization between two different AB stacked homobilayers could facilitate the condensation of inter-layer excitons, that could explain the non-magnetic insulating phases obtained in twisted homobilayers of WSe2. Also a Curie-Weiss 1/T behavior of the magnetic susceptibility has been reported for this material pointing to the formation of local moments, a hallmark of strong correlations. However, the precise nature of such an insulating phase has not yet been determined for the excitonic order could coexist with a charge-transfer insulator, Mott insulator or it could lead to a supersolid phase. |
Monday, March 6, 2023 4:36PM - 4:48PM |
D30.00009: Mott Transition in the Triangular Lattice Hubbard Model Pierre-Olivier Downey, Olivier Gingras, Maxime Charlebois, Charles-David Hebert Although the pseudogap in the weak interaction regime is mostly understood, in the strong interaction regime it still poses an important challenge for the understanding of hole-doped cuprates. It has been proposed that short-range antiferromagnetic (AFM) correlations and Mott physics are part of the mechanism involved in its formation [1]. Critics of this work have argued that the use of small clusters could artificially induce the first order transition [2], or that the apparent Mott transition is just a magnetic transition. To resolve this issue, we solve the Hubbard model using the dynamical cluster approximation on larger triangular clusters, where long-range AFM fluctuations are prohibited by geometrical frustration. Using the Widom line, we show that the Mott transition might exist in such systems and that a pseudogap appears at half filling [3]. |
Monday, March 6, 2023 4:48PM - 5:00PM Author not Attending |
D30.00010: Resistivity Anisotropy and Epitaxial Strain of Rare-Earth Nickelates on STO using Pulsed Laser Deposition Holland K Frieling, Angel Martinez, Andrew Yang, Jordan Zuniga, Gregorio Ponti, John T Markert We report x-ray diffraction, electrical resistivity, and atomic force microscopy measurements on uniform thin-film and half-thin-and-half-thick film NdNiO3 specimens to probe the effect of varying film thickness on transport properties. In particular, we exploit the strain-induced conductivity of epitaxial ultrathin films of NdNiO3 as a means to make contact to the bottom of a thicker film, and thus access anisotropic resistivity measurements. We shadow-mask to create a single sample with thinner and thicker portions, enabling electrical contact to both conducting and insulating phases. These devices are also intended for antiferromagnetic spin tunneling measurements in a similar fashion to a magnetic tunnel junction. The samples are prepared by annealing SrTiO3 (STO) substrates (950°C for ~2 hours) and depositing NdNiO3 at 650°C using pulsed laser deposition (PLD) with a KrF excimer laser (λ = 245 nm, pulse duration = 25 ns) and a phase-mixed but stoichiometric target. To optimize oxygen content, a partial pressure of O2 (about 150 mTorr) is introduced to the PLD chamber during deposition. |
Monday, March 6, 2023 5:00PM - 5:12PM Author not Attending |
D30.00011: Investigating the electronic charge and magentic spin dynamics in the ferromagnetic semiconductor HgCr2Se4 using resistance fluctuation (noise) spectroscopy Charu Garg, Zhilin Li, Youguo Shi, Jens Müller The n-type HgCr2Se4 has been reported to exhibit a pronounced semiconductor-to-metal transition below and a CMR effect at the ferromagnetic transition at TC = 107 K. Our recent study of charge carrier dynamics using resistance fluctuation spectroscopy [Phys. Rev B 105, 064404 (2022)] suggests isolated magnetic polarons forming at T > 2TC which coalesce at TC. Below this temperature, the trapped carriers in magnetic polarons are unbound in the presence of a magnetic field. The peculiar slow dynamics around this percolation transition has been discussed using a model where the effective radius of the polarons is strongly influenced by the spin correlation length close to TC. In this talk, we discuss new results highlighting the strong correlation between the magnetic and electronic degrees of freedom that can lead to complex exchange pathways. Likely due to competing AF and FM interactions, we observe a distinctly slow decrease in resistance below the CMR transition. The striking dynamics of distinct two-level fluctuations superimposed on 1/f-type noise corroborates a slowing down of charge carrier and/or magnetic dynamics. Further, below 20 K, a strong upturn in resistance and simultaneously in resistance noise down to 500 mK is observed and is speculated to be linked to the emergence of spiral type magnetic order. Our results demonstrate that the presence of pronounced electron-spin correlations plays a key role in the unconventional temperature dependence of resistance and CMR effect in this spinel. |
Monday, March 6, 2023 5:12PM - 5:24PM |
D30.00012: Filament localization and resistive switching power reduction in VOx via focused ion irradiation Nareg Ghazikhanian, Javier del Valle, Pavel Salev, Ralph El Hage, Yoav Kalcheim, Coline Adda, IVAN K SCHULLER Numerous materials exhibit resistive switching, a useful property which lends well to implementation of bioinspired electronic devices, notably artificial neurons and synapses for neuromorphic computing. In many systems, this effect occurs through the percolation of conducting filaments across an insulating matrix. Often, the location and switching parameters are impacted by inherent material defects, which poses a serious challenge for scalability of neuromorphic circuits. By selectively engineering defects using a focused ion beam, we report a novel method of locally tuning a material's electronic properties (i.e. conductivity and metal-insulator transition temperature) and by extension, controlling the location and shape of the conducting filament. In addition to confining the filament to the irradiated region, we observe a greater than 3 orders of magnitude reduction in switching power. Our work demonstrates that local ion irradiation is an efficient tool for fine-tuning resistive switching properties. This offers promising avenues for new energy-efficient biomimetic circuitry. |
Monday, March 6, 2023 5:24PM - 5:36PM |
D30.00013: Origins of Visible Light Emission upon Resistive Switching in NbO2 Mahnaz Islam, Stephanie M Bohaichuk, Timothy D Brown, Christopher Perez, Chengyang Zhang, Tae Joon Park, A. Alec Talin, Shriram Ramanathan, Suhas Kumar, Eric pop Future computing aims to integrate both electrical and optical components to gain high on-chip functional density. Here we present the discovery of a light emission occurring simultaneously with neuron-like resistive switching in electrical devices made of NbO2, a Mott insulator-metal-transition material [1]. We uncover that upon resistive switching, the NbO2 device emits light, with a peak in the visible wavelengths, measured via in-situ emission spectroscopy. We evaluate the measured emission spectra against pure blackbody models to understand their possible thermal origins. Further, we perform in-situ Raman spectroscopy during electrical switching, calibrated with ambient-temperature-controlled NbO2 films, to investigate electronic origins of the observed light emission. We rely upon previously reported band structure for these NbO2 thin films to assess our findings [2]. Our conclusion illustrates the possible thermal and electronic origins of light emission observed in electrically-switched NbO2. This discovery of an unprecedented light emission coupled with neuron-like switching in NbO2 has potential applications for metrology, electro-optical transduction, and on-chip light sources. |
Monday, March 6, 2023 5:36PM - 5:48PM |
D30.00014: Interaction corrections to the thermopower of the disordered two-dimensional electron gas Zahidul Islam Jitu, Georg Schwiete At low temperatures, there exist quantum corrections to transport coefficients in the disordered electron gas caused by the complex interplay of disorder and interactions. It is known that the thermal conductivity acquires Altshuler-Aronov corrections from virtual processes with electronic energies far above temperature. However, recent studies show that real processes give rise to additional interaction corrections to the thermal conductivity. This observation motivated us to study the interaction correction $delta S$ to the thermopower $S$ in the disordered electron gas. We show that while both real and virtual processes contribute to the interaction corrections of the thermopower, the real processes are dominant and lead to a logarithmic temperature dependence of $delta S/S$ with $delta S/S<0$. |
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