Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session J54: Mott Insulators and Fermi Fluids 
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Sponsoring Units: GMAG Chair: Clarina dela Cruz, Oak Ridge National Laboratory Room: Mile High Ballroom 1B 
Tuesday, March 4, 2014 2:30PM  2:42PM 
J54.00001: Probing the World of Correlated electron systems: Materials Characterization and Neutron Scattering studies Clarina dela Cruz An important field of experimental Condensed Matter Physics focuses on studying correlated electron systems including unconventional superconductors, ironbased superconductors and multifunctional systems such as multiferroic compounds. The use of various bulk measurement techniques to characterize the physical properties in these systems is an essential first step in revealing the novel electronic and magnetic ground states. Further studies using powerful microscopic probes such as neutron scattering methods are crucial in advancing the central theme in understanding correlated electron systems, which is to make the correlation between structure, magnetism and physical properties. As is common across correlated electron systems, highly degenerate ground states abound which are readily disturbed by chemical dopants and perturbing fields such as an applied magnetic field or pressure. Thus, studying these systems, using neutron scattering techniques in particular, in various extreme conditions reveals new emergent ground states with tunable magnetic, electronic or ferroelectric order parameters. [Preview Abstract] 
Tuesday, March 4, 2014 2:42PM  2:54PM 
J54.00002: Novel Itinerant Antiferromagnet With Nonmagnetic Constituents Eteri Svanidze, Jiakui Wang, Tiglet Besara, Monica Gamza, Theo Siegrist, Meigan Aronson, Andryi Nevidomskyy, Emilia Morosan While many systems exhibit both local and itinerant magnetism, only two are known to display magnetism while being composed of nonmagnetic elements  Sc$_3$In and ZrZn$_2$. Drastic differences in dimensionality, critical scaling and susceptibility to perturbations suggest that more systems like this would be useful in identifying the origin of their magnetic properties. In this talk, the properties of a new itinerant antiferromagent with no magnetic constituents, are presented. Specific heat, resistivity and magnetization data indicate magnetic ordering below $T_N \approx$ 36 K. Above this temperature, the susceptibility displays CurieWeisslike behavior, with an unexpectedly large paramagnetic moment $\mu_{PM}\approx 0.8~\mu_B~F.U.^{1}$. The magnetism is confirmed by band structure calculations, which suggest a spindensity wave ground state with a modulation wavevector $Q$ = $(0, 2\pi/3b, 0)$. [Preview Abstract] 
Tuesday, March 4, 2014 2:54PM  3:06PM 
J54.00003: Phase interference and subfemtosecond time dynamics of resonant inelastic Xray scattering from Mott insulators L. Andrew Wray, ShihWen Huang, Yuqi Xia, M. Zahid Hasan, Charles Mathy, Hiroshi Eisaki, Zahid Hussain, YiDe Chuang Resonant inelastic Xray scattering (RIXS) is a powerful technique for observing the energy states of manybody quantum materials. The core hole resonance states that make RIXS possible are strongly correlated, and undergo complex time evolution that shapes scattering spectra. However, current inelastic scattering measurements cannot be converted to a time resolved picture, because techniques that determine relative phase information from elastic scattering have not been adapted to the greater complexity of inelastic spectra. We will show that inelastic scattering phases can be identified from quantum interference in sharply resolved (dE $<$ 35meV) Medge RIXS spectra of Mott insulators (e.g. SrCuO$_2$ and NiO), and provide new information for identifying excitation symmetries and manybody time dynamics. [Preview Abstract] 
Tuesday, March 4, 2014 3:06PM  3:18PM 
J54.00004: Novel magnetic state in $d^4$ Mott insulators Oinam Nganba Meetei, William Cole, Mohit Randeria, Nandini Trivedi We show that the interplay of strong Hubbard interaction $U$ and spinorbit coupling $\lambda$ in systems with the $d^4$ electronic configuration leads to several unusual magnetic phases. While in the atomic limit the system is in a nonmagnetic $J=0$ singlet state, we find that the competition between superexchange and atomic spinorbit coupling dramatically changes the local moment, which challenges the conventional wisdom that local moments are welldefined in a Mott insulator. Most notably, we find that in the Mott limit at strong $U$ there is a phase transition from a nonmagnetic insulator of uncoupled $J=0$ singlets to an orbitally entangled ferromagnetic insulator. We identify candidate materials and present predictions for Resonant Xray Scattering (RXS) signatures for the unusual magnetism in $d^4$ Mott insulators and contrast them with the wellstudied $d^5$ case. [Preview Abstract] 
Tuesday, March 4, 2014 3:18PM  3:30PM 
J54.00005: Mott Glass Phase in the Disordered Quantum Spin Systems DaoXin Yao, Nvsen Ma, Anders Sandvik We use quantum Monte Carlo method to study the disordered $S=1/2$ quantum spins on the square lattice with three different nearest neighbor interactions $J_{1}$, $J_{2}$ and $J_{3}$. Here $J_{1}$ represents weak bonds, and $J_{2}$ and $J_{3}$ correspond to stronger bonds which are randomly distributed on columnar rungs forming coupled 2leg ladders. By tuning the average value of $J_{2}$ and $J_{3}$, the system undergoes N$\acute{e}$elglassparamagnetic quantum phase transition. A wide range of Mott glass phase has been found. We notice that its uniform susceptibility in the glass phase follows $ \chi\sim\exp(b/T^{\alpha})$, where $0.5<\alpha<1$. Furthermore, this dimerized disordered quantum spin system shows the violation of Harris criterion. [Preview Abstract] 
Tuesday, March 4, 2014 3:30PM  3:42PM 
J54.00006: Fractionalized liquid states in doped Mott insulators Andrej Mesaros, Shenghan Jiang, Ying Ran We study Mott insulator phases at specifically chosen doping levels on several lattices. Using analytical and numerical techniques we identify interesting quantum liquid phases with fractionalized excitations. [Preview Abstract] 
Tuesday, March 4, 2014 3:42PM  3:54PM 
J54.00007: Ultrafast dynamics of the nanoscale metalinsulator transition in VO$_2$ Joanna Atkin, Brian O'Callahan, Sven Doenges, Andrew Jones, Markus Raschke The metalinsulator transition (MIT) of vanadium dioxide (VO$_2$) exhibits a rich phase behavior involving two monoclinic (M1, M2), a triclinic, and a tetragonal phase that form a complex domain structure and lead to spatial inhomogeneities in the electronic transition. The interplay of these different phases with strain can affect the progress of both the thermal and photoinduced MIT. We report on nanooptical imaging of the MIT in individual microcrystals and thin films of VO$_2$, in order to probe the effects of substrate and crystallite strain, morphology, and orientation on the emergent metallic phase. We find a large variation in transition rates and dynamical behavior among single crystal microrods, indicating intrinsic inhomogeneities in the MIT. [Preview Abstract] 
Tuesday, March 4, 2014 3:54PM  4:06PM 
J54.00008: Iridate spin models: magnetism, 3D spin liquids and an infiniteD entanglement approximation Itamar Kimchi, James Analytis, Ashvin Vishwanath We present threedimensional threefoldcoordinated structures for iridates which may generate Kitaevtype magnetic exchanges. The resulting solvable 3D quantum spin liquid exhibits the uniquely 3D property of stability to finite temperature ($T_c \sim J_k/100$). Adding Heisenberg couplings spoils exact solubility; however, the large loop length $\ell$ of the lattice suggests an approximation with large $\ell \rightarrow \infty$. The KitaevHeisenberg model can be solved on the resulting Bethe lattice using tensor product states; we present the phase diagrams, finding multiple magnetic order parameters and identifying gapped spin liquid phases by an entanglement fingerprint. [Preview Abstract] 
Tuesday, March 4, 2014 4:06PM  4:18PM 
J54.00009: Ferromagnetism in flat bands and Paulicorrelated percolation Mykola Maksymenko, Andreas Honecker, Roderich Moessner, Johannes Richter, Oleg Derzhko, Kirill Shtengel Flatband ferromagnetism is an exotic case of itinerantelectron magnetism in a wide class of geometrically frustrated lattices. We develop an exact mapping between the ground state of the manybody problem and a novel sitepercolation problem. This allows us to study the ferromagnetic transition using tools from equilibrium statistical physics. In the case of Hubbard model on the Tasaki lattice, we provide a complete and exact solution in 1D and show that for D $>$ 1, the paramagnetic phase persist beyond the uncorrelated percolation point, with a transition in the form of a firstorder jump to an unsaturated ferromagnetic phase. [Preview Abstract] 
Tuesday, March 4, 2014 4:18PM  4:30PM 
J54.00010: Theory of spin density wave glasses David Mross, T. Senthil We study the effects of nonmagnetic impurities on an easyplane spin density wave at $\vec Q$ accompanied by a charge density wave at $2\vec Q$ in two and three dimensions. Even though any amount of disorder dramatically reduces both spin and charge correlations, spin nematic correlations remain essentially unaffected. This is due to the proliferation of only certain kinds of defects, leading to a uniaxial spin glass. The presence of a Goldstone mode distinguishes this phase from a conventional spin glass, and can serve as an experimental signature. Similarly, in superconductors with finite momentum pairing, a charge4 condensate persists in the presence of weak disorder, while pair density wave order (the FFLO state) is lost due to impurities. [Preview Abstract] 
Tuesday, March 4, 2014 4:30PM  4:42PM 
J54.00011: Excitations of a Fermi fluid with coupled magnetic and nematic order parameters Pengtao Shen, Khandker Quader We study possible stable phases of 2D and 3D Fermi fluids with coupled magnetic and nematic order parameters by considering appropriate GinzburgLandau free energies, and performing necessary minimizations. In Fermi liquid language, nematic order corresponds to L=2 distortions of the Fermi surface, so here we consider such distortions in a magnetically ordered Fermi fluid. We use Landau kinetic equation to study propagating collective modes and corresponding dispersions of the modes. [Preview Abstract] 
Tuesday, March 4, 2014 4:42PM  4:54PM 
J54.00012: Lowtemperature evolution of the spectral weight of a spinup carrier moving in a ferromagnetic background Mirko Moeller, Mona Berciu The motion of a charged particle in a magnetically ordered background determines the electronic behavior of many weakly doped, magnetically ordered insulators and semiconductors. This problem can be solved exactly for a single charge carrier in a ferromagnetic background at T=0. There are two different cases to be considered (i) the carrier spin is oriented antiparallel with respect to the FM background and (ii) the carrier spin is aligned with the background. For the former case the solution is a spinpolaron, a dressed quasiparticle consisting of a charged particle and a bound magnon. For the latter case, on the other hand, the formation of a spinpolaron is impossible at T=0 due to the absence of spinflip excitations. The T=0 spectrum of the spinup carrier is therefore identical to that of a free carrier shifted by the $z$part of the magnetic interaction. This changes at finiteT where thermal magnons are present in the system. To study this change, we derived the lowestT correction to the selfenergy of the spinup carrier. This allows us to investigate how the T=0 quasiparticle peak broadens into a continuum at finiteT. Furthermore we find that spectral weight is shifted to energies outside of this continuum, which can be associated with the spinpolaron state. [Preview Abstract] 
Tuesday, March 4, 2014 4:54PM  5:06PM 
J54.00013: Plaquette ordered phase and quantum spin liquid in the spin1/2 J1J2 square Heisenberg model Shoushu Gong, Wei Zhu, Olexei I. Motrunich, Matthew P.A. Fisher, DongNing Sheng We study the spin1/2 Heisenberg model on the square lattice with first and secondneighbor antiferromagnetic interactions $J_1$ and $J_2$. We use the density matrix renormalization group with implementing $SU(2)$ spin rotation symmetry and study the model accurately on open cylinders with different boundary conditions. With increasing $J_2$, we find a N\'{e}el phase, a plaquette valencebond (PVB) phase with a finite spin gap, and a possible spin liquid in a small region of $J_2$ between these two phases. From the finitesize scaling of the magnetic order parameter, we estimate that the N\'{e}el order vanishes at $J_2/J_1\simeq 0.44$. For $0.5 < J_2/J_1 < 0.61$, we find dimer correlations and PVB textures whose decay length grows strongly with increasing system width, consistent with a longrange PVB order in the twodimensional limit. The dimerdimer correlation function reveals the swave character of the PVB order. For $0.44 < J_2/J_1 < 0.5$, both spin and dimer orders are weak on finitesize systems and appear to scale to zero with increasing system width, which is consistent with a possible SL or a nearcritical behavior. We compare and contrast our results with earlier numerical studies. [Preview Abstract] 

J54.00014: ABSTRACT WITHDRAWN 
Tuesday, March 4, 2014 5:18PM  5:30PM 
J54.00015: Fragile antiferromagnetic order in the heavyfermion YbBiPt B.G. Ueland, A. Kreyssig, K. Proke\v{s}, J.W. Lynn, L.W. Harriger, D.K. Pratt, D.K. Singh, T.W. Heitmann, S. Sauerbrei, S.M. Saunders, E.D. Mun, S.L. Bud'ko, R.J. McQueeney, P.C. Canfield, A.I. Goldman YbBiPt is a heavyfermion compound ($\gamma\approx$ 8 J/molK$^2$) possessing antiferromagnetic order below a N\'{e}el temperature of $T_{\rm{N}}$= 0.4 K, and a proposed quantum critical point at a magnetic field of $H_{\rm{c}}\approx$ 0.4 T. We report results from neutron scattering experiments on single crystals which characterize the antiferromagnetic order. The magnetic scattering is described in terms of two components: a narrow component that appears below $T_{\rm{N}}$ which corresponds to the onset of antiferromagnetic order observed in bulk thermodynamic and transport measurements, and a broad component corresponding to antiferromagnetic correlations extending over $\approx$ 20 $\rm{\AA}$ that persists up to $T^{\rm{*}}\approx$ 0.7 K. These results illustrate the unconventional nature of the magnetism in YbBiPt and may be a consequence of its competing lowenergy magnetic interactions and proximity to a quantum critical point.\\ Work at the Ames Laboratory was supported by the Department of Energy, Basic Energy Sciences under Contract No. DEAC0207CH11358. [Preview Abstract] 
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