Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session G63: Metal-Insulator Transitions: Theory and ExperimentRecordings Available
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Sponsoring Units: DCMP Chair: Tarapada Sarkar, University of Maryland Room: Hyatt Regency Hotel -Grant Park A |
Tuesday, March 15, 2022 11:30AM - 11:42AM |
G63.00001: Applications of Nickelate perovskites for neuromorphic computing from electronic structure and Machine Learning Soumya S Bhat, Uthpala K Herath, Bilvin Varughese, Andres Tellez, Logan L Lang, Sukriti Manna, Subramanian Sankaranarayanan, Aldo H Romero Metal to insulator (MIT) transition present in strongly correlated materials (SCM) is crucial in designing materials for neuromorphic applications, as they show great sensibility to small environment changes. We performed studies on controlling MIT in SCM’s through means of DMFT calculations. Our in-house DMFTwDFT framework provided DMFT total energies of various strongly correlated bulk SmNiO3 and GdNiO3 configurations mimicking a Boltzmann distribution under a Debye model at a finite temperature that was used to train an atomic interaction potential based on artificial neural networks (ANN). Results indicate very good correlation between the DMFT energies, and the total energies predicted by the machine learning model. Next, we introduce oxygen vacancies in order to tune the MIT and incorporate that for training the machine learning model. We also study the oxygen vacancy diffusion energy barrier through means of Nudged Elastic Band analysis and DMFT to elucidate the effect of vacancy migration on MIT. Elastic constants are calculated from DMFT energy calculations and are fed to the NN potential. The relation between the deformation and the energy obtained from DMFT allow us to describe the role of vacancies to create distortions which impact the electronic properties. |
Tuesday, March 15, 2022 11:42AM - 11:54AM Withdrawn |
G63.00002: Site occupation disorder study of oxygen vacancies in LaNiO3 Uthpala K Herath, Hyowon Park, Vijay R Singh, Benny Wah, Soumya Bhat, Aldo H Romero Due to the strong coupling between multiple degrees of freedom, oxygen vacancies in complex oxides lead to a variety of intriguing emergent phenomena. Manipulating oxygen vacancies in strongly correlated rare-earth nickelate perovskites (RNO3) enables the tuning of their elusive metal-insulator transition (MIT) providing a better handle for band-gap engineering. However, as the number of vacancies in a system increases, the possible configurational space of vacancy structures rises drastically, rendering a computational study of them quite expensive. Here, we study the effects of oxygen vacancies on the electronic properties of the correlated perovskite LaNiO3 in the R3c space group using a combination of density functional theory and dynamical mean field theory (DFT+DMFT). We utilize a symmetry-adapted configurational ensemble method to obtain a reduced configurational space, thus lowering the computational cost. By treating both Ni-eg and Ni-t2g as correlated orbitals, we show that certain configurations undergo a MIT based on the positioning of their vacancies. We also compare the single oxygen vacancy diffusion energy through means of the nudged elastic band (NEB) method considering non-magnetic (NM), ferromagnetic (FM) and anti-ferromagnetic (AFM-I, AFM-II) ordering. |
Tuesday, March 15, 2022 11:54AM - 12:06PM |
G63.00003: Insulator-to-metal transition in Bi2Ru2O7 pyrochlores: role of the uncorrelated Bi off-centering Danilo Puggioni, Geneva Laurita, Ram Seshadri, James M Rondinelli Understanding the insulator-to-metal transitions (IMT) in complex oxides is of fundamental interest both from the theoretical and applicative point of view. |
Tuesday, March 15, 2022 12:06PM - 12:18PM |
G63.00004: Landau Theory for Disorder-Driven Metal-Insulator Transitions Yuting Tan, Vladimir Dobrosavljevic Disorder driven metal-insulator transitions have long defied proper understanding, despite representing one of the basic phenomena in solid state physics. Here we first provide a brief overview of key experimental features, providing guidance. We then present a new theoretical approach that makes it possible to formulate Landau-like order parameter theory at the saddle-point level, capturing most experimental puzzles. It also allows an investigation of systematic fluctuation corrections, suggesting a finite upper critical dimension, and a formulation of an appropriate Landau-Ginzburg description of spatial correlations currently studied by scanning probes. |
Tuesday, March 15, 2022 12:18PM - 12:30PM |
G63.00005: Quantum Monte Carlo Study of the electronic properties of delafossite 2H-AgNiO2 and AgNixCo1-xO2 Hyeondeok Shin, Panchapakesan Ganesh, Paul Kent, Anouar Benali, Anand Bhattacharya, Ho Nyung Lee, Olle Heinonen The delafossite AgNiO2 has received a great deal of attention due to its unique semi-metallic nature, which only AgNiO2 exhibits among the d10-based delafossites, and its antiferromagnetism in the NiO2 layers. Due to the semi-metallic nature of AgNiO2, the existence of a metal-insulator transition has been predicted in AgNixCo1-xO2 structures consisting of an admixture of insulating CoO2 into the NiO2. The electronic structure of AgNiO2 have been studied using Density Functional Theory (DFT), but a detailed predictive study that includes accurate electron correlations in NiO2 has been missing. Using Quantum Monte Carlo method, we obtain accurate estimates for the electronic properties of AgNiO2. We also conclude that the rather strong electron correlations in AgNiO2 were underestimated in DFT studies. Finally, we study various compositions of AgNixCo1-xO2 and estimate their formation energies and band gap openings with Co substitutions in order to investigate the electronic properties and phase stability of the mixtures. |
Tuesday, March 15, 2022 12:30PM - 12:42PM |
G63.00006: The Real Space Typical Medium Cluster Theory of Anderson Localization Hanna Terletska, Ka Ming Tam, Tom Berlijn, Liviu Chioncel, Juana Moreno We develop a real space cluster extension of the typical medium theory (cluster-TMT) to study Anderson localization in disordered materials [1]. By construction, the cluster-TMT approach is formally equivalent to the real space cluster extension of the dynamical mean-field theory (CDMFT). Applying the developed method to the 3D Anderson model with a box disorder distribution, we demonstrate that cluster-TMT successfully captures the localization phenomena in all disorder regimes. As a function of the cluster size, our method obtains the correct critical disorder strength for the Anderson localization and systematically recovers the re-entrance behavior of the mobility edge. From a general perspective, our developed methodology offers the potential to study Anderson localization at surfaces within quantum embedding theory. This opens the door to studying the interplay between topology and Anderson localization from first principles. |
Tuesday, March 15, 2022 12:42PM - 12:54PM |
G63.00007: Theory of a Continuous Bandwidth-tuned Wigner-Mott Transition Seth W Musser, Senthil Todadri, Debanjan Chowdhury We develop a theory for a continuous bandwidth-tuned transition at fixed fractional electron filling from a metal with a generic Fermi surface to a `Wigner-Mott' insulator that spontaneously breaks crystalline space-group symmetries. Across the quantum critical point, (i) the entire electronic Fermi surface disappears abruptly upon approaching from the metallic side, and (ii) the insulating charge gap and various order-parameters associated with the spontaneously broken space-group symmetries vanish continuously upon approaching from the insulating side. Additionally, though the electronic Fermi surface vanishes, the spinon Fermi surface remains on the insulating side. We present a framework for describing such continuous metal-insulator transitions (MIT) and analyze the example of a bandwidth-tuned transition at a filling, $\nu=1/6$, for spinful electrons on the triangular lattice. By extending the theory to a certain large-$N$ limit, we provide a concrete example of such a continuous MIT and discuss numerous experimental signatures near the critical point. We place our results in the context of recent experiments in moir\'e transition metal dichalcogenide materials. |
Tuesday, March 15, 2022 12:54PM - 1:06PM |
G63.00008: Lattice fluctuation induced pseudogap in quasi-one-dimensional Ta2NiSe5 Cheng Chen, Xiang Chen, Weichen Tang, Zhenglu Li, Siqi Wang, shuhan ding, Christopher Jozwiak, Aaron Bostwick, Eli Rotenberg, Makoto Hashimoto, Donghui Lu, Jacob Ruff, Steven G Louie, Robert J Birgeneau, Yulin Chen, Yao Wang, Yu He In conventional solid-state systems, the development of an energy gap is often associated with a broken symmetry. However, strongly correlated materials can exhibit energy gaps without any global symmetry breaking -- the so-called pseudogap, most notably in the Mott insulating state and the fluctuating superconducting or charge density wave states. Combining angle-resolved photoemission spectroscopy (ARPES) and single crystal x-ray diffraction, we identify a pseudogap in the quasi-1D excitonic insulator candidate Ta2NiSe5. Strong lattice contribution is revealed by the pervasive diffuse scattering well above the transition temperature, and the negative electronic compressibility in the pseudogap state. Combining first-principles and microscopic model calculations, we show that inter-band electron-phonon coupling can create fluctuating phonon-mediated electron-hole pairs or hybridization, suppressing the spectral weight near EF and causing a metal-to-insulator like transition without breaking the global symmetry. This highlights Ta2NiSe5 as a promising room-temperature platform to study lattice-induced charge localization and low dimensional fluctuations. |
Tuesday, March 15, 2022 1:06PM - 1:18PM |
G63.00009: Insulator-Metal Transition in Two-dimensional Mott Insulator NiPS3 under pressure Takahiro Matsuoka, Rui Xue, Amanda V Haglund, Jesse S Smith, Maik Lang, Antonio M dos Santos, David G Mandrus NiPS3 crystallizes in a monoclinic C2/m structure at ambient pressure. The Ni ions form a honeycomb lattice, and each layer is isolated between two layers of S and P triangles (PS3), separated by van der Waals (vdW) gaps. Below 155 K, NiPS3 orders anti-ferromagnetically with the magnetic moment directed mostly along the c axis.1 There is a prediction that pressure-induced Mott insulator to metal transition (IMT) might be accompanied by the |SZ| = 1 to |SZ| = 1/2 state without changing crystal structure.2 The electronically-driven IMT suggests that NiPS3 is a promising material for ultrafast resistivity switching. We performed electrical resistance and XRD measurements under quasi-uniaxial pressure and observed a sluggish IMT at 35 GPa accompanied by a structure change. This work did not observe superconductivity down to 2 K in contrast to FePSe3 (max Tc ~ 5.5 K at 30 GPa)4. The observed structure evolution differs from earlier reports that applied a different pressure media.3 It is suggested that the phase stability fields of NiPS3 are highly dependent on the stress state. |
Tuesday, March 15, 2022 1:18PM - 1:30PM |
G63.00010: Quantum oscillations in interaction-driven insulators Andrew A Allocca, Nigel R Cooper In recent years it has become understood that quantum oscillations, long recognized as phenomena intrinsic to metals, can manifest in insulating systems as well. Simple models have shown that in band insulators oscillations can appear with a frequency set by the area in momentum space traced out by the minimum gap. Here we examine quantum oscillations in Kondo and excitonic insulators, systems for which the band gap is generated by interaction effects. In both cases, the gapped band structure is dependent on parameters that are determined self-consistently and vary with the applied magnetic field strength, so that the bands are not "rigid" as the field changes and new contributions to quantum oscillations can be generated on top of what is expected from a simple band insulator. We analyze these contributions in the low-temperature, low-field regime, finding that they do not contribute to the lowest harmonic of quantum oscillations but provide the dominant contribution to all higher harmonics. We also examine the contribution from fluctuations of the insulating order. |
Tuesday, March 15, 2022 1:30PM - 1:42PM |
G63.00011: Elastic stripes formation at metal-insulator transitions Giuliano Chiriaco, Andrew J Millis We consider a general model of an electronic metal-insulator transition coupled to the elastic degrees of freedom of the lattice, and investigate the possibility of an emerging inhomogeneous phase, made by alternating stripes with metallic and insulating behavior, as the system crosses the transition. We solve the general elastic equations and minimize the total free energy of the system. We find that a stripe pattern may emerge for electronic transitions of either first order and second order. Stripes are stabilized when the typical elastic energy gained by forming the stripes overcomes the typical electronic and domain wall energy costs, and when they extend across the entire depth of the system. We also study the behavior of the metallic phase fraction as function of temperature across the spinodal region of a first order phase transition. |
Tuesday, March 15, 2022 1:42PM - 1:54PM |
G63.00012: Thermodynamic Properties of the Extended Hubbard Model from Quantum Monte Carlo Alexander Sushchyev, Stefan Wessel We use determinantal quantum Monte Carlo simulations to study the thermal properties of the extended Hubbard model on the square lattice at half-filling. In particular, we consider the effect of a nearest-neighbor repulsion on the thermal metal-to-insulator transition in the Slater-regime of the Hubbard model within the parameter regime accessible to sign-free quantum Monte Carlo simulations. Upon exploring in detail the temperature dependence of the double occupancy, we probe for signatures of a first-order metal-to-insulator transition, as proposed in M.Schueler, et al.,SciPost Phys. 6, 067 (2019), driven by the suppression of correlation effects by the non-local interactions. |
Tuesday, March 15, 2022 1:54PM - 2:06PM |
G63.00013: A first-principles study of the structural phase transition in Ta2NiSe5 Weichen Tang, Zhenglu Li, Steven G Louie Ta2NiSe5, a quasi one-dimensional material, undergoes a structural phase transition from a high temperature orthorhombic phase to a low temperature monoclinic phase at around 330K, accompanied by a transition from metal to insulator. Previous studies suggest that the transition may be driven by formation of excitons and the low temperature phase of Ta2NiSe5 is a possible candidate for an excitonic insulator phase. We have performed density functional theory (DFT) calculations to investigate the structural and electronic properties of this system. Simulations of structural changes as a function of temperature and charge doping are consistent with the observed monoclinic-orthorhombic structural transition, and the corresponding electronic structure shows good agreement with recent angle-resolved photoemission spectroscopy (ARPES) data [1]. Further analysis of the electronic structure of the system will be presented. |
Tuesday, March 15, 2022 2:06PM - 2:18PM |
G63.00014: Nonhermitian Green's function formalism for metal-insulator transition Sumanta Bandyopadhyay, Alexander V Balatsky Landau formulated a concept of Fermi liquid (FL) by adiabatically turning on interaction in a non-interacting Fermi-gas. Such evolution results in a one-to-one correspondence between excitations in the Fermi gas and the quasiparticles in the FL. Quasiparticle picture in the FL, however, breaks down when the self-energy term in the Green's function becomes non-analytic. Understanding the non-trivial physics beyond FL theory posits an open challenge in condensed matter physics. To deal with the non-analyticity of the self-energy of the Green's function, we have studied Green's function formalism for a general non-hermitian Hamiltonian in a bi-orthogonal basis. The non-hermitian term is finally set to zero to achieve a general Green's function formalism for the hermitian system. While we restore the well-studied structure of the retarded and advanced Green's function for a hermitian system by imposing an extra condition of the analyticity of the Green's function, we showed that such constraints on analyticity are no longer valid when FL theory breaks down and we get a different perturbative expansion of the Green's function. In this process, we have constructed an order parameter for the breaking down of the FL theory. For the particle-hole symmetric Hubbard model, this order parameter coincides with the order parameter of the Hubbard-I approximation. |
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