Bulletin of the American Physical Society
Mid-Atlantic Section 2022 Meeting
Volume 67, Number 20
Friday–Sunday, December 2–4, 2022; University Park, PA, Pennsylvania State University
Session D04: Solid State, Magnetism, and Superconductivity |
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Chair: Benjamin Katz, Pennsylvania State University Room: Pennsylvania State University Osmond 106 |
Saturday, December 3, 2022 11:00AM - 11:35AM |
D04.00001: Modelling 2D materials at Chemical Accuracy Invited Speaker: Can Ataca Recent advancements in computational power enabled researchers to focus on more accurate methodologies for simulating materials properties. This talk will focus on modeling two dimensional (2D) materials using Quantum Monte Carlo Methodology (QMC) and benchmarking it with experimental results. First part of the talk will focus on modeling properties of 2D GaSe monolayers for device applications where optical and electronic properties are benchmarked with other simulations methodologies and experimental data. Second part of the talk will focus on alloying 2D GaSe with GaS for tunability of optoelectronic properties. A novel approach to conduct high-throughput QMC simulations for alloys will be detailed. Third and fourth part of the talk focuses on magnetic 2D materials. Correlated electrons and induced magnetic moments are the main point of failures for much of the functionals of Density Functional Theory (DFT) methodology. In the last 2 parts, the talk will focus on method to overcome these failures and provide a pathway for predicting magnetic properties using QMC at chemical accuracy. The materials of focus will be on MnO2 and VSe2 monolayers and their competing phases. Methods to stabilize one phase over other will be detailed as well. Understanding the chemistry at atomistic scale and achieving chemical accuracy in material simulations will enable device realization of 2D materials for the next generation opto-electronic and magnetic devices. |
Saturday, December 3, 2022 11:35AM - 11:47AM |
D04.00002: Topologically-Driven Conductivity and Gapping in Graphene Benjamin Katz, Vincent H Crespi, Paul E Lammert Disclinated sp2 carbon surfaces show a clear pattern in their density of states (DOS) with the separation of these disclinations. This arises from the effect of the topology of the π-bonding network on phase matching around these disclinations, and can produce a striking scaling behavior of the DOS to a level of fine detail within an energy window determined by the areal density of the disclinations. Motivated by the presumed existence of a low-energy continuum description of the system, which should give a scaling of DOS that varies inversely with the separation of disclinations, we look for this scaling and find it exists in families grouped by their separation in distance in the bond network, much like the (n-m) mod 3 rule for carbon nanotubes. These groupings (and their associated spacings mod 3) predict whether a specific structure has a gapped DOS at the Fermi energy, and the size of the gaps in the gapped structures are of the order predicted by a low-energy continuum model description. Notably, this behavior (including the scaling of the DOS) persists down to separations where the disclinations are not significantly distant from each other, and a continuum model would not be anticipated to work well. |
Saturday, December 3, 2022 11:47AM - 11:59AM |
D04.00003: Plasmonic epsilon-near-zero (ENZ) engineering for electron-phonon interaction (EPI) Jiantao Kong Electron scattering in a general solid-state material consisting of electrons, phonons, impurities, etc. could be viewed as scattering by a screened Coulomb potential with a total epsilon packing up contributions from all the components [1,2,3,4]. Wherever there is a singularity in the imaginary part of one over epsilon, i.e., the condition of epsilon near zero (ENZ) [6], there is a mode (collective excitation) in the system [5]. We show in this context, as a prototype, that electron-polar-optical-phonon scattering could be quenched by an additional fine-tuned plasmonic resonance introduced to the system. This could serve as a general engineering trick which might have applications in many fields. The physics picture is, polarization of the newly added resonance, with frequency and strength fine-tuned, could destructively interfere with and cancel out polarization of the original resonance of the system. |
Saturday, December 3, 2022 11:59AM - 12:11PM |
D04.00004: Spin-relaxation of Defect Center Qubit by Off-Resonant Pinned Domain Wall Oscillations Jeffrey G Rable, Jyotirmay Dwivedi, Nitin Samarth The nitrogen-vacancy (NV) center, a fluorescent defect in diamond, has emerged as a powerful room temperature quantum sensor for probing the local properties of ferromagnetic textures; for example, it has been used for static imaging of domain walls (DW) [Nat. Commun.6, 6733 (2015] and skyrmions [Nat Commun. 9, 2712 (2018)], as well as dynamic measurements of magnetic vortex gyrations [J. Appl. Phys., 130, 083903 (2021)]. Here, we demonstrate off-resonant spin relaxation of NV centers in deterministically placed nanodiamonds via the GHz-scale oscillations of a pinned DW. By placing the nanodiamonds over a pinning site determined by a notch in the wire and shape anisotropy, we reliably measure the spin dynamics of both a nucleated and denucleated control case. Then, we compare these results to micromagnetic simulations to further confirm our results. This work expands the menagerie of magnetization dynamics that can be detected with NV centers and builds the foundation for future DW qubit coupling experiments, presenting a powerful new avenue for local microwave driving and qubit addressability. |
Saturday, December 3, 2022 12:11PM - 12:23PM |
D04.00005: Controlling Cavity-Mediated Superconductivity with Quantum States of Light Ahana Chakraborty, Francesco Piazza Recent success in coupling electrons in two-dimensional materials to the quantum electromagnetic field of optical cavities has opened up many exciting but yet unexplored avenues of quantum electrodynamics, among which one promising idea is to use the photons in the cavity to mediate pairing between electrons, inducing superconducting states with novel properties. An exciting prospect, that makes photons the more interesting mediator with respect to the phonons of the standard BCS paradigm, is to exploit state-of-the-art engineering of the quantum states of light to control superconductivity. A naturally emerging question, which remains still open, is whether one can enhance superconductivity by feeding the cavity with certain quantum states of the photons. This new playground for quantum many-body physics is at the same time exciting and theoretically challenging to describe, requiring us to develop new approaches merging quantum optics, condensed matter, and quantum-field-theory. We recently developed a non-equilibrium field-theory approach that allows to tackle this question. I will describe our current understanding of the problem focusing on how critical properties of the superconducting transitions can be manipulated by initialising the photons in non-thermal initial density matrices. |
Saturday, December 3, 2022 12:23PM - 12:35PM |
D04.00006: Dynamic melting and condensation of topological dislocation modes Sanjib Kumar Das, Bitan Roy Bulk dislocation lattice defects are instrumental to identify translationally active topological insulators (TATIs), featuring band inversion at a finite momentum (Kinv). They harbor robust gapless modes around the dislocation core, when the associated Burgers vector (b) satisfies Kinv · b = π (modulo 2π). From the time evolution of the appropriate density matrix, here we show that when a TATI via a ramp enters into a trivial or topological insulating phase, devoid of any gapless dislocation mode, at least weak signatures of the original defect modes survive for a long time. More intriguingly, as the system ramps into a TATI phase, signature of the dislocation mode dynamically builds up. Such evolutions of dislocation modes are more prominent for slow ramps. We exemplify these generic outcomes for two-dimensional time-reversal symmetry breaking insulators. Proposed dynamic responses at the core of dislocation lattice defects can be experimentally observed on quantum crystals, optical lattices and various metamaterials with time tunable band gap. |
Saturday, December 3, 2022 12:35PM - 12:47PM |
D04.00007: Nodal pair-density-waves from quarter-metal in crystalline graphene multilayers. Sk Asrap Murshed, Bitan Roy, Andras Szabo Crystalline graphene heterostructures, namely Bernal bilayer and rhombohedral trilayer graphene, subject to electric displacement fields, display a rich confluence of competing orders, resulting in a valley-degenerate, spin-polarized half-metal at moderate doping, and a spin- and valley-polarized quarter-metal at low doping. Here we show that the annular Fermi surface of such a quarter-metal can be susceptible toward the nucleation of a unique spin and valley polarized superconducting state, accommodating interlayer Cooper pairs that break the translational symmetry, giving rise to a Kekulé or columnar pair-density-wave. The superconducting ground state produces isolated Fermi pockets of neutral Majorana fermions, featuring a three-fold rotational symmetry, resulting in power-law scaling physical observables with temperature (T), such as specific heat Cv∼T. |
Saturday, December 3, 2022 12:47PM - 12:59PM |
D04.00008: Are normal band insulators topologically distinguishable? Sanjib Kumar Das, Bitan Roy Over the past 15 years topological classification of solids has occupied the center stage of condensed matter physics, identifying a variety of topologically distinct quantum phases of matter in real materials. Although the sector of topological crystals is sufficiently rich and diverse, populated by strong, weak, crystalline and higher-order topological insulators, for example, all the normal or trivial insulators are considered to be equally mundane. Here we ask the following question: Can normal insulators be topologically distinct? and provide an affirmative answer to it. We consider a paradigmatic toy lattice model, featuring topological quantum anomalous Hall insulators and trivial or normal insulators. Within the framework of this model, we show that the parent normal insulators, realized via band gap closing around the gamma and M points, accommodate distinct topological superconductors, which can be probed by dislocation lattice defects. Namely, only the superconductor resulting from the latter parent normal insulator responds to bulk dislocation defects by binding topological Majorana modes near its core. Therefore, normal insulators can be distinguishable once superconductivity develops in the system. We anchor this prediction by computing their response to dislocations as well as from quantized thermal Hall conductivity. |
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