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Articles 1 - 30 of 32
Full-Text Articles in Physics
Non-Abelian Quasiholes In Lattice Moore-Read States And Parent Hamiltonians, Sourav Manna, Julia Wildeboer, Germán Sierra, Anne E. B. Nielsen
Non-Abelian Quasiholes In Lattice Moore-Read States And Parent Hamiltonians, Sourav Manna, Julia Wildeboer, Germán Sierra, Anne E. B. Nielsen
Physics and Astronomy Faculty Publications
This work concerns Ising quasiholes in Moore-Read type lattice wave functions derived from conformal field theory. We commence with constructing Moore-Read type lattice states and then add quasiholes to them. By use of Metropolis Monte Carlo simulations, we analyze the features of the quasiholes, such as their size, shape, charge, and braiding properties. The braiding properties, which turn out to be the same as in the continuum Moore-Read state, demonstrate the topological attributes of the Moore-Read lattice states in a direct way. We also derive parent Hamiltonians for which the states with quasiholes included are ground states. One advantage of …
Unconventional Anomalous Hall Effect From Antiferromagnetic Domain Walls Of Nd2Ir2O7 Thin Films, Woo Jin Kim, John H. Gruenewald, Taekoo Oh, Sangmo Cheon, Bongju Kim, Oleksandr B. Korneta, Hwanbeom Cho, Daesu Lee, Yoonkoo Kim, Miyoung Kim, Je-Geun Park, Bohm-Jung Yang, Ambrose Seo
Unconventional Anomalous Hall Effect From Antiferromagnetic Domain Walls Of Nd2Ir2O7 Thin Films, Woo Jin Kim, John H. Gruenewald, Taekoo Oh, Sangmo Cheon, Bongju Kim, Oleksandr B. Korneta, Hwanbeom Cho, Daesu Lee, Yoonkoo Kim, Miyoung Kim, Je-Geun Park, Bohm-Jung Yang, Ambrose Seo
Physics and Astronomy Faculty Publications
Ferroic domain walls (DWs) create different symmetries and ordered states compared with those in single-domain bulk materials. In particular, the DWs of an antiferromagnet with noncoplanar spin structure have a distinct symmetry that cannot be realized in those of their ferromagnet counterparts. In this paper, we show that an unconventional anomalous Hall effect (AHE) can arise from the DWs of a noncoplanar antiferromagnet, Nd2Ir2O7. Bulk Nd2Ir2O7 has a cubic symmetry; thus, its Hall signal should be zero without an applied magnetic field. The DWs generated in this material break …
Observation Of A Pressure-Induced Transition From Interlayer Ferromagnetism To Intralayer Antiferromagnetism In Sr4Ru3O10, H. Zheng, W. H. Song, J. Terzic, H. D. Zhao, Y. F. Ni, Lance E. Delong, P. Schlottmann, G. Cao
Observation Of A Pressure-Induced Transition From Interlayer Ferromagnetism To Intralayer Antiferromagnetism In Sr4Ru3O10, H. Zheng, W. H. Song, J. Terzic, H. D. Zhao, Y. F. Ni, Lance E. Delong, P. Schlottmann, G. Cao
Physics and Astronomy Faculty Publications
Sr4Ru3O10 is a Ruddlesden-Popper compound with triple Ru-O perovskite layers separated by Sr-O rock-salt layers. This compound presents a rare coexistence of interlayer (c-axis) ferromagnetism and intralayer (basal-plane) metamagnetism at ambient pressure. Here we report the observation of pressure-induced, intralayer itinerant antiferromagnetism arising from the interlayer ferromagnetism. The application of modest hydrostatic pressure generates an anisotropy that may cause a flattening and a tilting of RuO6 octahedra. All magnetic and transport results from this study indicate these lattice distortions diminish the c-axis ferromagnetism and basal-plane metamagnetism, and induce a basal-plane antiferromagnetic state. …
Kelvin-Mach Wake In A Two-Dimensional Fermi Sea, Eugene B. Kolomeisky, Joseph P. Straley
Kelvin-Mach Wake In A Two-Dimensional Fermi Sea, Eugene B. Kolomeisky, Joseph P. Straley
Physics and Astronomy Faculty Publications
The dispersion law for plasma oscillations in a two-dimensional electron gas in the hydrodynamic approximation interpolates between Ω ∝ √q and Ω ∝ q dependences as the wave vector q increases. As a result, downstream of a charged impurity in the presence of a uniform supersonic electric current flow, a wake pattern of induced charge density and potential is formed whose geometry is controlled by the Mach number M. For 1 < M ≤ √2, the wake consists of transverse wave fronts confined within a sector, whose angle is given by the classic Mach condition. An additional wake of …
Quadrupolar Quantum Criticality On A Fractal, Jonathan D'Emidio, Simon Lovell, Ribhu K. Kaul
Quadrupolar Quantum Criticality On A Fractal, Jonathan D'Emidio, Simon Lovell, Ribhu K. Kaul
Physics and Astronomy Faculty Publications
We study the ground state ordering of quadrupolar ordered S = 1 magnets as a function of spin dilution probability p on the triangular lattice. In sharp contrast to the ordering of S = 1/2 dipolar Néel magnets on percolating clusters, we find that the quadrupolar magnets are quantum disordered at the percolation threshold, p = p∗. Further we find that long-range quadrupolar order is present for all p < p∗ and vanishes first exactly at p∗. Strong evidence for scaling behavior close to p∗ points to an unusual quantum criticality without fine tuning that …
Coexistence Of Ferromagnetism And Unconventional Spin-Glass Freezing In The Site-Disordered Kagome Ferrite Srsn2Fe4O11, L. Shlyk, S. Strobel, Barry Farmer, Lance E. De Long, R. Niewa
Coexistence Of Ferromagnetism And Unconventional Spin-Glass Freezing In The Site-Disordered Kagome Ferrite Srsn2Fe4O11, L. Shlyk, S. Strobel, Barry Farmer, Lance E. De Long, R. Niewa
Physics and Astronomy Faculty Publications
Single-crystal x-ray diffraction refinements indicate SrSn2Fe4O11 crystallizes in the hexagonal R-type ferrite structure with noncentrosymmetric space group P63mc and lattice parameters a = 5.9541(2)Å, c = 13.5761(5)Å, Z = 2 (R(F) = 0.034). Octahedrally coordinated 2a [M(1) and M(1a)] and 6c sites [M(2)] have random, mixed occupation by Sn and Fe; whereas the tetrahedrally coordinated 2b sites [Fe(3) and Fe(3a)] are exclusively occupied by Fe, whose displacement from the ideal position with trigonal-bipyramidal coordination causes the loss of inversion symmetry. …
Electronic And Optical Properties Of La-Doped Sr3Ir2O7 Epitaxial Thin Films, Maryam Souri, Jsaminka Terzic, J. M. Johnson, John G. Connell, John H. Gruenewald, J. Thompson, Joseph W. Brill, J. Hwang, Gang Cao, Sung S. Ambrose Seo
Electronic And Optical Properties Of La-Doped Sr3Ir2O7 Epitaxial Thin Films, Maryam Souri, Jsaminka Terzic, J. M. Johnson, John G. Connell, John H. Gruenewald, J. Thompson, Joseph W. Brill, J. Hwang, Gang Cao, Sung S. Ambrose Seo
Physics and Astronomy Faculty Publications
We have investigated structural, transport, and optical properties of tensile strained (Sr1−xLax)3Ir2O7 (x = 0, 0.025, 0.05) epitaxial thin films. While high-Tc superconductivity is predicted theoretically in the system, we have observed that all of the samples remain insulating with finite optical gap energies and Mott variable-range hopping characteristics in transport. Cross-sectional scanning transmission electron microscopy indicates that structural defects such as stacking faults appear in this system. The insulating behavior of the La-doped Sr3Ir2O7 thin films is presumably due to disorder-induced …
Mutual Influence Between Macrospin Reversal Order And Spin-Wave Dynamics In Isolated Artificial Spin-Ice Vertices, F. Montoncello, L. Giovannini, Wonbae Bang, J. B. Ketterson, M. B. Jungfleisch, A. Hoffmann, Barry W. Farmer, Lance E. De Long
Mutual Influence Between Macrospin Reversal Order And Spin-Wave Dynamics In Isolated Artificial Spin-Ice Vertices, F. Montoncello, L. Giovannini, Wonbae Bang, J. B. Ketterson, M. B. Jungfleisch, A. Hoffmann, Barry W. Farmer, Lance E. De Long
Physics and Astronomy Faculty Publications
We theoretically and experimentally investigate magnetization reversal and associated spin-wave dynamics of isolated threefold vertices that constitute a Kagome lattice. The three permalloy macrospins making up the vertex have an elliptical cross section and a uniform thickness. We study the dc magnetization curve and the frequency versus field curves (dispersions) of those spin-wave modes that produce the largest response. We also investigate each macrospin reversal from a dynamic perspective, by performing micromagnetic simulations of the reversal processes, and revealing their relationships to the soft-mode profile calculated at the equilibrium state immediately before reversal. The theoretical results are compared with the …
Origin Of The Exciton Mass In The Frustrated Mott Insulator Na2Iro3, Zhanybek Alpichshev, Edbert J. Sie, Fahad Mahmood, Gang Cao, Nuh Gedik
Origin Of The Exciton Mass In The Frustrated Mott Insulator Na2Iro3, Zhanybek Alpichshev, Edbert J. Sie, Fahad Mahmood, Gang Cao, Nuh Gedik
Physics and Astronomy Faculty Publications
We use a three-pulse ultrafast optical spectroscopy to study the relaxation processes in a frustrated Mott insulator Na2IrO3. By being able to independently produce the out-of-equilibrium bound states (excitons) of doublons and holons with the first pulse and suppress the underlying antiferromagnetic order with the second one, we were able to elucidate the relaxation mechanism of quasiparticles in this system. By observing the difference in the exciton dynamics in the magnetically ordered and disordered phases we found that the mass of this quasiparticle is mostly determined by its interaction with the surrounding spins.
Spin Mode Switching At The Edge Of A Quantum Hall System, Udit Khanna, Ganpathy Murthy, Sumathi Rao, Yuval Gefen
Spin Mode Switching At The Edge Of A Quantum Hall System, Udit Khanna, Ganpathy Murthy, Sumathi Rao, Yuval Gefen
Physics and Astronomy Faculty Publications
Quantum Hall states can be characterized by their chiral edge modes. Upon softening the edge potential, the edge has long been known to undergo spontaneous reconstruction driven by charging effects. In this Letter we demonstrate a qualitatively distinct phenomenon driven by exchange effects, in which the ordering of the edge modes at ν = 3 switches abruptly as the edge potential is made softer, while the ordering in the bulk remains intact. We demonstrate that this phenomenon is robust, and has many verifiable experimental signatures in transport.
Screening And Plasma Oscillations In An Electron Gas In The Hydrodynamic Approximation, Eugene B. Kolomeisky, Joseph P. Straley
Screening And Plasma Oscillations In An Electron Gas In The Hydrodynamic Approximation, Eugene B. Kolomeisky, Joseph P. Straley
Physics and Astronomy Faculty Publications
A hydrodynamic theory of screening in a generic electron gas of arbitrary dimensionality is given that encompasses all previously studied cases and clarifies the predictions of the many-body approach. We find that long-wavelength plasma oscillations are classical phenomena with quantum-mechanical effects playing no explicit role. The character of the oscillations is solely dictated by the dimensionality of the electron system and its equation of state in the neutral limit. Materials whose excitations are described by the Dirac dispersion law—such as doped graphene or a Weyl semimetal—are no exception to this rule.
Evidence For A Low-Temperature Magnetic Ground State In Double-Perovskite Iridates With Ir5+(5D4) Ions, Jasminka Terzic, H. Zheng, Feng Ye, H. D. Zhao, P. Schlottmann, Lance E. De Long, S. J. Yuan, Gang Cao
Evidence For A Low-Temperature Magnetic Ground State In Double-Perovskite Iridates With Ir5+(5D4) Ions, Jasminka Terzic, H. Zheng, Feng Ye, H. D. Zhao, P. Schlottmann, Lance E. De Long, S. J. Yuan, Gang Cao
Physics and Astronomy Faculty Publications
We report an unusual magnetic ground state in single-crystal, double-perovskite Ba2YIrO6 and Sr-doped Ba2YIrO6 with Ir5+(5d4) ions. Long-range magnetic order below 1.7 K is confirmed by dc magnetization, ac magnetic susceptibility, and heat-capacity measurements. The observed magnetic order is extraordinarily delicate and cannot be explained in terms of either a low-spin S = 1 state, or a singlet Jeff = 0 state imposed by the spin-orbit interactions (SOI). Alternatively, the magnetic ground state appears consistent with a SOI that competes with comparable Hund's rule coupling and inherently large …
Optical Signatures Of Spin-Orbit Exciton In Bandwidth-Controlled Sr2Iro4 Epitaxial Films Via High-Concentration Ca And Ba Doping, Maryam Souri, B. H. Kim, John H. Gruenewald, John G. Connell, J. Thompson, J. Nichols, Jsaminka Terzic, B. I. Min, Gang Cao, Joseph W. Brill, Sung S. Ambrose Seo
Optical Signatures Of Spin-Orbit Exciton In Bandwidth-Controlled Sr2Iro4 Epitaxial Films Via High-Concentration Ca And Ba Doping, Maryam Souri, B. H. Kim, John H. Gruenewald, John G. Connell, J. Thompson, J. Nichols, Jsaminka Terzic, B. I. Min, Gang Cao, Joseph W. Brill, Sung S. Ambrose Seo
Physics and Astronomy Faculty Publications
We have investigated the electronic and optical properties of (Sr1−xCax)2IrO4 (x = 0–0.375) and (Sr1−yBay)2IrO4 (y = 0–0.375) epitaxial thin films, in which the bandwidth is systematically tuned via chemical substitutions of Sr ions by Ca and Ba. Transport measurements indicate that the thin-film series exhibits insulating behavior, similar to the Jeff = 1/2 spin-orbit Mott insulator Sr2IrO4. As the average A-site ionic radius increases from (Sr1−xCax)2IrO4 to (Sr …
New Easy-Plane CpN−1 Fixed Points, Jonathan D'Emidio, Ribhu K. Kaul
New Easy-Plane CpN−1 Fixed Points, Jonathan D'Emidio, Ribhu K. Kaul
Physics and Astronomy Faculty Publications
We study fixed points of the easy-plane CPN−1 field theory by combining quantum Monte Carlo simulations of lattice models of easy-plane SU(N) superfluids with field theoretic renormalization group calculations, by using ideas of deconfined criticality. From our simulations, we present evidence that at small N our lattice model has a first-order phase transition which progressively weakens as N increases, eventually becoming continuous for large values of N. Renormalization group calculations in 4−ε dimensions provide an explanation of these results as arising due to the existence of an Nep that separates the fate of …
Predicted Electronic Markers For Polytypes Of Laobis2 Examined Via Angle-Resolved Photoemission Spectroscopy, Xiaoqing Zhou, Qihang Liu, J. A. Waugh, T. Nummy, Xiuwen Zhang, Xiangde Zhu, Gang Cao, Alex Zunger, D. S. Dessau
Predicted Electronic Markers For Polytypes Of Laobis2 Examined Via Angle-Resolved Photoemission Spectroscopy, Xiaoqing Zhou, Qihang Liu, J. A. Waugh, T. Nummy, Xiuwen Zhang, Xiangde Zhu, Gang Cao, Alex Zunger, D. S. Dessau
Physics and Astronomy Faculty Publications
The natural periodic stacking of symmetry-inequivalent planes in layered compounds can lead to the formation of natural superlattices; albeit close in total energy, (thus in their thermodynamic stability), such polytype superlattices can exhibit different structural symmetries, thus have markedly different electronic properties which can in turn be used as “structural markers”. We illustrate this general principle on the layered LaOBiS2 compound where density-functional theory (DFT) calculations on the (BiS2)/(LaO)/(BiS2) polytype superlattices reveal both qualitatively and quantitatively distinct electronic structure markers associated with the Rashba physics, yet the total energies are only ∼ 0.1 meV apart. …
Structure And Physical Properties Of Srniru5O11 Single Crystals: An R-Type Ferrite Based On Ordered Kagome Nets, L. Shlyk, Lance E. De Long, R. Niewa
Structure And Physical Properties Of Srniru5O11 Single Crystals: An R-Type Ferrite Based On Ordered Kagome Nets, L. Shlyk, Lance E. De Long, R. Niewa
Physics and Astronomy Faculty Publications
Single crystals of the R-type ferrite SrNiRu5O11 were grown from a chloride flux. The hexagonal crystal structure contains ruthenium located on distorted kagome nets. The low-temperature dc magnetic susceptibilities (χ⊥ and χ∥, perpendicular and parallel to the c axis, respectively) diverge as T−0.3, and do not exhibit any indication of long-range magnetic order down to 4.5 K. The electrical resistivity varies as T1.6 below 40 K, which is typical of non-Fermi liquids, and may originate from a competition between residual magnetic interactions among Ni2+ (S = 1) spins …
Relaxation Of Charge In Monolayer Graphene: Fast Nonlinear Diffusion Versus Coulomb Effects, Eugene B. Kolomeisky, Joseph P. Straley
Relaxation Of Charge In Monolayer Graphene: Fast Nonlinear Diffusion Versus Coulomb Effects, Eugene B. Kolomeisky, Joseph P. Straley
Physics and Astronomy Faculty Publications
Pristine monolayer graphene exhibits very poor screening because the density of states vanishes at the Dirac point. As a result, charge relaxation is controlled by the effects of zero-point motion (rather than by the Coulomb interaction) over a wide range of parameters. Combined with the fact that graphene possesses finite intrinsic conductivity, this leads to a regime of relaxation described by a nonlinear diffusion equation with a diffusion coefficient that diverges at zero charge density. Some consequences of this fast diffusion are self-similar superdiffusive regimes of relaxation, the development of a charge depleted region at the interface between electron- and …
Doping Evolution Of Magnetic Order And Magnetic Excitations In (Sr1-XLaX)3Ir2O7, Xingye Lu, D. E. Mcnally, M. Moretti Sala, Jsaminka Terzic, M. H. Upton, D. Casa, G. Ingold, Gang Cao, T. Schmitt
Doping Evolution Of Magnetic Order And Magnetic Excitations In (Sr1-XLaX)3Ir2O7, Xingye Lu, D. E. Mcnally, M. Moretti Sala, Jsaminka Terzic, M. H. Upton, D. Casa, G. Ingold, Gang Cao, T. Schmitt
Physics and Astronomy Faculty Publications
We use resonant elastic and inelastic x-ray scattering at the Ir-L3 edge to study the doping-dependent magnetic order, magnetic excitations, and spin-orbit excitons in the electron-doped bilayer iridate (Sr1−xLax)3Ir2O7 (0 ≤ x ≤ 0.065). With increasing doping x, the three-dimensional long range antiferromagnetic order is gradually suppressed and evolves into a three-dimensional short range order across the insulator-to-metal transition from x = 0 to 0.05, followed by a transition to two-dimensional short range order between x = 0.05 and 0.065. Because of the interactions between the J …
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 …
Temperature Dependent C-Axis Hole Mobilities In Rubrene Single Crystals Determined By Time-Of-Flight, Russell L. Lidberg, Tom J. Pundsack, Neale O. Haugen, Lucas R. Johnstone, C. Daniel Frisbie
Temperature Dependent C-Axis Hole Mobilities In Rubrene Single Crystals Determined By Time-Of-Flight, Russell L. Lidberg, Tom J. Pundsack, Neale O. Haugen, Lucas R. Johnstone, C. Daniel Frisbie
Physics and Astronomy Faculty Publications
Hole mobilities (μ) in rubrene single crystals (space group Cmca) along the crystallographic c-axis have been investigated as a function of temperature and applied electric field by the time-of-fight method. Measurements demonstrate an inverse power law dependence on temperature, namely,μ=μ0T−n with n = 1.8, from room temperature down to 180 K. At 296 K, the average value of μ was found to be 0.29 cm2/Vs increasing to an average value of 0.70 cm2/Vs at 180 K. Below 180 K a decrease in mobility is observed with further cooling. Overall, these results confirm the …
Evolution Of Magnetism In The Single-Crystal Honeycomb Iridates (Na1−XLiX)2Iro3, Gang Cao, Tongfei Qi, L. Li, Jsaminka Terzic, Vincent Shian Cao, Shujuan Yuan, M. Tovar, Ganpathy Murthy, Ribhu K. Kaul
Evolution Of Magnetism In The Single-Crystal Honeycomb Iridates (Na1−XLiX)2Iro3, Gang Cao, Tongfei Qi, L. Li, Jsaminka Terzic, Vincent Shian Cao, Shujuan Yuan, M. Tovar, Ganpathy Murthy, Ribhu K. Kaul
Physics and Astronomy Faculty Publications
We report the successful synthesis of single crystals of the layered iridate (Na1−xLix)2IrO3, 0 ≤ x ≤ 0.9, and a thorough study of its structural, magnetic, thermal, and transport properties. This compound allows a controlled interpolation between Na2IrO3 and Li2IrO3, while maintaining the quantum magnetism of the honeycomb Ir4+ planes. The measured phase diagram demonstrates a suppression of the Néel temperature TN at an intermediate x, indicating that the magnetic orders in Na2IrO3 and Li2IrO3 …