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Articles 1 - 10 of 10
Full-Text Articles in Physics
Evolution Of Network Architecture In A Granular Material Under Compression, Lia Papadopoulous, James G. Puckett, Karen E. Daniels, Danielle S. Bassett
Evolution Of Network Architecture In A Granular Material Under Compression, Lia Papadopoulous, James G. Puckett, Karen E. Daniels, Danielle S. Bassett
Physics and Astronomy Faculty Publications
As a granular material is compressed, the particles and forces within the system arrange to form complex and heterogeneous collective structures. Force chains are a prime example of such structures, and are thought to constrain bulk properties such as mechanical stability and acoustic transmission. However, capturing and characterizing the evolving nature of the intrinsic inhomogeneity and mesoscale architecture of granular systems can be challenging. A growing body of work has shown that graph theoretic approaches may provide a useful foundation for tackling these problems. Here, we extend the current approaches by utilizing multilayer networks as a framework for directly quantifying …
Skyrmions And Hall Transport, Bom Soo Kim, Alfred D. Shapere
Skyrmions And Hall Transport, Bom Soo Kim, Alfred D. Shapere
Physics and Astronomy Faculty Publications
We derive a generalized set of Ward identities that captures the effects of topological charge on Hall transport. The Ward identities follow from the (2+1)-dimensional momentum algebra, which includes a central extension proportional to the topological charge density. In the presence of topological objects like Skyrmions, we observe that the central term leads to a direct relation between the thermal Hall conductivity and the topological charge density. We extend this relation to incorporate the effects of a magnetic field and an electric current. The topological charge density produces a distinct signature in the electric Hall conductivity, which is identified in …
Interaction-Induced Dirac Fermions From Quadratic Band Touching In Bilayer Graphene, Sumiran Pujari, Thomas C. Lang, Ganpathy Murthy, Ribhu K. Kaul
Interaction-Induced Dirac Fermions From Quadratic Band Touching In Bilayer Graphene, Sumiran Pujari, Thomas C. Lang, Ganpathy Murthy, Ribhu K. Kaul
Physics and Astronomy Faculty Publications
We revisit the effect of local interactions on the quadratic band touching (QBT) of the Bernal honeycomb bilayer model using renormalization group (RG) arguments and quantum Monte Carlo (QMC) simulations. We present a RG argument which predicts, contrary to previous studies, that weak interactions do not flow to strong coupling even if the free dispersion has a QBT. Instead, they generate a linear term in the dispersion, which causes the interactions to flow back to weak coupling. Consistent with this RG scenario, in unbiased QMC simulations of the Hubbard model we find compelling evidence that antiferromagnetism turns on at a …
Pressure-Induced Confined Metal From The Mott Insulator Sr3Ir2O7, Yang Ding, Liuxiang Yang, Cheng-Chien Chen, Heung-Sik Kim, Myung Joon Han, Wei Luo, Zhenxing Feng, Mary Upton, Diego Casa, Jungho Kim, Thomas Gog, Zhidan Zeng, Gang Cao, Ho-Kwang Mao, Michel Van Veenendaal
Pressure-Induced Confined Metal From The Mott Insulator Sr3Ir2O7, Yang Ding, Liuxiang Yang, Cheng-Chien Chen, Heung-Sik Kim, Myung Joon Han, Wei Luo, Zhenxing Feng, Mary Upton, Diego Casa, Jungho Kim, Thomas Gog, Zhidan Zeng, Gang Cao, Ho-Kwang Mao, Michel Van Veenendaal
Physics and Astronomy Faculty Publications
The spin-orbit Mott insulator Sr3Ir2O7 provides a fascinating playground to explore insulator-metal transition driven by intertwined charge, spin, and lattice degrees of freedom. Here, we report high-pressure electric resistance and resonant inelastic x-ray scattering measurements on single-crystal Sr3Ir2O7 up to 63–65 GPa at 300 K. The material becomes a confined metal at 59.5 GPa, showing metallicity in the ab plane but an insulating behavior along the c axis. Such an unusual phenomenon resembles the strange metal phase in cuprate superconductors. Since there is no sign of the collapse of spin-orbit …
Direct Imaging Of Coexisting Ordered And Frustrated Sublattices In Artificial Ferromagnetic Quasicrystals, Barry Farmer, Vinayak Shantaram Bhat, Eric Teipel, J. Unguris, D. J. Keavney, Jeffrey Todd Hastings, Lance E. De Long
Direct Imaging Of Coexisting Ordered And Frustrated Sublattices In Artificial Ferromagnetic Quasicrystals, Barry Farmer, Vinayak Shantaram Bhat, Eric Teipel, J. Unguris, D. J. Keavney, Jeffrey Todd Hastings, Lance E. De Long
Physics and Astronomy Faculty Publications
We have used scanning electron microscopy with polarization analysis and photoemission electron microscopy to image the two-dimensional magnetization of permalloy films patterned into Penrose P2 tilings (P2T). The interplay of exchange interactions in asymmetrically coordinated vertices and short-range dipole interactions among connected film segments stabilize magnetically ordered, spatially distinct sublattices that coexist with frustrated sublattices at room temperature. Numerical simulations that include long-range dipole interactions between sublattices agree with images of as-grown P2T samples and predict a magnetically ordered ground state for a two-dimensional quasicrystal lattice of classical Ising spins.
Ground-State Tuning Of Metal-Insulator Transition By Compositional Variations In Bair1−XRuXO3 (0 ≤ X ≤ 1), Shujuan Yuan, Kamal H. Butrouna, Jsaminka Terzic, Hao Zheng, Saicharan Aswartham, Lance E. Delong, Feng Ye, P. Schlottmann, Gang Cao
Ground-State Tuning Of Metal-Insulator Transition By Compositional Variations In Bair1−XRuXO3 (0 ≤ X ≤ 1), Shujuan Yuan, Kamal H. Butrouna, Jsaminka Terzic, Hao Zheng, Saicharan Aswartham, Lance E. Delong, Feng Ye, P. Schlottmann, Gang Cao
Physics and Astronomy Faculty Publications
Hexagonal BaIrO3 is a magnetic insulator driven by the spin-orbit interaction (SOI), whereas BaRuO3 is an enhanced paramagnetic metal. Our investigation of structural, magnetic, transport, and thermal properties reveals that substitution of Ru4+ (4d4) ions for Ir4+ (5d5) ions in BaIrO3 reduces the magnitudes of the SOI and a monoclinic structural distortion and rebalances the competition between the SOI and the lattice degrees of freedom to render an evolution from a magnetic insulting state to a robust metallic state. The central findings of this paper are as follows: (1) light …
Emergence Of Helical Edge Conduction In Graphene At The Ν = 0 Quantum Hall State, Pavel Tikhonov, Efrat Shimshoni, H. A. Fertig, Ganpathy Murthy
Emergence Of Helical Edge Conduction In Graphene At The Ν = 0 Quantum Hall State, Pavel Tikhonov, Efrat Shimshoni, H. A. Fertig, Ganpathy Murthy
Physics and Astronomy Faculty Publications
The conductance of graphene subject to a strong, tilted magnetic field exhibits a dramatic change from insulating to conducting behavior with tilt angle, regarded as evidence for the transition from a canted antiferromagnetic (CAF) to a ferromagnetic (FM) ν = 0 quantum Hall state. We develop a theory for the electric transport in this system based on the spin-charge connection, whereby the evolution in the nature of collective spin excitations is reflected in the charge-carrying modes. To this end, we derive an effective field-theoretical description of the low-energy excitations, associated with quantum fluctuations of the spin-valley domain-wall ground-state configuration which …
First-Order Superfluid To Valence-Bond Solid Phase Transitions In Easy-Plane Su(N) Magnets For Small N, Jonathan D'Emidio, Ribhu K. Kaul
First-Order Superfluid To Valence-Bond Solid Phase Transitions In Easy-Plane Su(N) Magnets For Small N, Jonathan D'Emidio, Ribhu K. Kaul
Physics and Astronomy Faculty Publications
We consider the easy-plane limit of bipartite SU(N) Heisenberg Hamiltonians, which have a fundamental representation on one sublattice and the conjugate to fundamental on the other sublattice. For N = 2 the easy plane limit of the SU(2) Heisenberg model is the well-known quantum XY model of a lattice superfluid. We introduce a logical method to generalize the quantum XY model to arbitrary N, which keeps the Hamiltonian sign-free. We show that these quantum Hamiltonians have a world-line representation as the statistical mechanics of certain tightly packed loop models of N colors in which neighboring loops are …
Ν = 1/2 Landau Level: Half-Empty Versus Half-Full, Ganpathy Murthy, R. Shankar
Ν = 1/2 Landau Level: Half-Empty Versus Half-Full, Ganpathy Murthy, R. Shankar
Physics and Astronomy Faculty Publications
We show here that an extension of the Hamiltonian theory developed by us over the years furnishes a composite fermion (CF) description of the ν = 1/2 state that is particle-hole (PH) symmetric, has a charge density that obeys the magnetic translation algebra of the lowest Landau level (LLL), and exhibits cherished ideas from highly successful wave functions, such as a neutral quasiparticle with a certain dipole moment related to its momentum. We also a provide an extension away from ν = 1/2, which has the features from ν = 1/2 and implements the PH transformation on the LLL as …
Collective Bulk And Edge Modes Through The Quantum Phase Transition In Graphene At Ν = 0, Ganpathy Murthy, Efrat Shimshoni, H. A. Fertig
Collective Bulk And Edge Modes Through The Quantum Phase Transition In Graphene At Ν = 0, Ganpathy Murthy, Efrat Shimshoni, H. A. Fertig
Physics and Astronomy Faculty Publications
Undoped graphene in a strong, tilted magnetic field exhibits a radical change in conduction upon changing the tilt angle, which can be attributed to a quantum phase transition from a canted antiferromagnetic (CAF) to a ferromagnetic (FM) bulk state at filling factor ν = 0. This behavior signifies a change in the nature of the collective ground state and excitations across the transition. Using the time-dependent Hartree-Fock approximation, we study the collective neutral (particle-hole) excitations in the two phases, both in the bulk and on the edge of the system. The CAF has gapless neutral modes in the bulk, whereas …