Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session E07: Correlated Chains and Ladders 
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Sponsoring Units: DCMP Chair: Satya Kushwaha, Los Alamos National Laboratory Room: BCEC 109B 
Tuesday, March 5, 2019 8:00AM  8:12AM 
E07.00001: Outofequilibrium transverse field XY chain  nonequilibrium phase transitions, transport, and entanglement Tharnier O. Puel, Stefano Chesi, Stefan Kirchner, Pedro Ribeiro The generalization of quantum phase transitions to nonequilibrium conditions raises a number of questions, in particular, if and how outofequilibrium critical phenomena can be categorized into universality classes, in analogy with thermal equilibrium. 
Tuesday, March 5, 2019 8:12AM  8:24AM 
E07.00002: Estimates of the Quantum Fisher Information in the $S=1$ AntiFerromagnetic Heisenberg Spin Chain with Uniaxial Anisotropy James Lambert, Erik Sorensen The quantum Fisher information has relevance to quantum metrology and as an entanglement measure. We focus on the $S=1$ antiferromagnetic Heisenberg model with uniaxial anisotropy. 
Tuesday, March 5, 2019 8:24AM  8:36AM 
E07.00003: Reduced density operators of finitesized Heisenberg XXZ chains Bohan Lu, Alexander Seidel In quantum manybody physics, reduced density operators play a central role in revealing the properties of a given system. We elaborate on this by studying finite size Heisenberg XXZ chains in the presence of periodic boundary conditions. As pointed out by F. Verstraete and J. Cirac, the admissible (2site) local density matrices form a convex set determined by compatibility with translational invariance. The density matrices of ground states of translationally invariant nearestneighbor Hamiltonians will define the boundary of this set. It is hard to determine this boundary without actually solving for manybody ground states, as knowledge of it would give immediate access to ground state energies of a rich class of models. Here we present studies on the size dependence of this mysterious boundary manifold. We also discuss nonanalyticities of the boundary characterizing quantum phase transitions in the thermodynamic limit. 
Tuesday, March 5, 2019 8:36AM  8:48AM 
E07.00004: Localization in a t − J type ladder with translational symmetry Rongyang Sun, Zheng Zhu, ZhengYu Weng An explicit spatial localization of a hole is shown in a twoleg tJ ladder in the presence of a staggered chemical potential, which still retains translational symmetry, by density matrix renormalization group method. Delocalization can be recovered in following cases, in which either the hidden phase string effect is turned off or a finite nextneighbor hopping t′ is added to sufficiently weaken the phase string effect. In particular, two holes are always delocalized by forming a mobile bound pair in contrast to the localized single holes, pointing to a novel pairing mechanism of strong correlation nature. 
Tuesday, March 5, 2019 8:48AM  9:00AM 
E07.00005: Flexible magnetism in flexible crystals Elise Kenny, Anthony C Jacko, Ben J Powell We predict that the elastically flexible crystal, [Cu(acac)_{2}] [1], contains quasionedimensional magnetic interactions that change dramatically when the crystal is bent. In the unbent crystal, all interchain interactions are doubly frustrated – geometrically and by the equipoise of antiferromagnetic and ferromagnetic interactions in the two planes perpendicular to the chains. We parametrize a Heisenberg model for the unbent and bent crystal from brokensymmetry density functional theory [2], revealing that the intrachain exchange interaction is an order of magnitude larger than the interchain exchange interactions. We calculate the three dimensional Néel temperature, T_{N}, from the chain random phase approximation (CRPA) [3], which reveals that [Cu(acac)_{2}] is an almost perfect TomonagaLuttinger liquid (TLL) with a T_{N} that increases by approximately 175 orders of magnitude when the material is bent. This is a proof of principle demonstration that magnetic properties can be significantly altered by bending flexible crystals. 
Tuesday, March 5, 2019 9:00AM  9:12AM 
E07.00006: Ladderlike optical conductivity in the spinfermion model Laura Classen, Neil Robinson, Alexei Tsvelik In the nested limit of the spinfermion model for the cuprates, 1Dtype physics in the form of halffilled twoleg ladders emerges. We show that the RG flow of the corresponding ladder is towards the dMott phase, a gapped spinliquid with shortranged dwave pairing correlations, and reveals an intermediate SO(5)xSO(3) symmetry. We use the results of the RG in combination with a memoryfunction approach to calculate the optical conductivity of the spinfermion model in the highfrequency regime, where processes within the hotspot region dominate the transport. For finite temperature, we determine the resistivity in the zerofrequency limit. We argue that Umklapp processes play a major role. Our results show an approximate linear temperature dependence of the resistivity and a conductivity that follows a nonuniversal power law, qualitatively consistent with experiment. 
Tuesday, March 5, 2019 9:12AM  9:24AM 
E07.00007: Spectrum of Dissipative Ising Chain Jian Wang, Sudip Chakravarty This paper extends the (0+1)D spinboson problem to its (1+1)D version, a dissipative Ising Chain. 
Tuesday, March 5, 2019 9:24AM  9:36AM 
E07.00008: Singlecomponent fermion chain: emergent mode and liquids of bound states Yuchi He, Binbin Tian, David Pekker, Roger Mong We study the formation of bound states in a singlecomponent Fermi chain with attractive interactions. 
Tuesday, March 5, 2019 9:36AM  9:48AM 
E07.00009: Spontaneous SUSY breaking and NG modes in interacting Majorana chains Noriaki Sannomiya, Hosho Katsura The relation between spontaneous symmetry breaking and NambuGoldstone (NG) modes has been well studied for conventional bosonic symmetries. On the other hand, the corresponding relation for spontaneous supersymmetry (SUSY) breaking in nonrelativistic systems is less understood. To fill this gap, we have studied the properties of nonrelativistic systems with N=2 SUSY in [1, 2]. However, properties of N=1 SUSY are still elusive. 
Tuesday, March 5, 2019 9:48AM  10:00AM 
E07.00010: MajoranaHubbard Ladders Armin Rahmani, Dmitry Pikulin, Ian Affleck

Tuesday, March 5, 2019 10:00AM  10:12AM 
E07.00011: Ising ferromagnet to valence bond solid transition in a onedimensional spin chainanalogies to deconfined quantum critical points Shenghan Jiang, Olexei I Motrunich We study a 1D system that shows many analogies to proposed 2D deconfined quantum critical points. Our system is a translationally invariant spin1/2 chain with onsite Z2×Z2 symmetry and time reversal symmetry. It undergoes a direct continuous transition from a ferromagnet (FM), where one of the Z2 symmetries and the time reversal are broken, to a valence bond solid (VBS), where all onsite symmetries are restored while the translation symmetry is broken. The other Z2 symmetry remains unbroken throughout, but its presence is crucial for both the direct transition and the characterization of the VBS phase. The transition has a description in terms of either two domain wall species that "fractionalize" the VBS order parameter or in terms of partons that "fractionalize" the FM order parameter. The two descriptions are dual to each other. We also find an exact reformulation of the transition that leads to a simple field theory description that explicitly unifies the two order parameters, which can be interpreted as a new parton approach that encodes the two order parameters in instantons. 
Tuesday, March 5, 2019 10:12AM  10:24AM 
E07.00012: Xray resonant scattering study on the minor canted moment of spin1 1 dimensional chain system NiTe_{2}O_{5} Donghwan Kim, KyungTae Ko, Younghak Kim, Yoon Seok Oh, JaeHoon Park A minor canted component of antiferromagnetic order below T_{N} ~ 30.5 K of NiTe_{2}O_{5} was investigated by the soft xray resonant scattering on Ni L_{3} edge. It is a S=1 (Ni^{2+}) magnetic insulator composed of edge shared NiO_{6} one dimensional chains along b axis with four Ni atoms per period. The nearly 90° superexchange path between two adjacent Ni stabilizes intrachain ferromagnetic order along b axis, which is ordered antiferromagnetically between adjacent chains. A detailed analysis on the azimuthal and polarization dependence of the (010) structural forbidden peak reveals that the resonant peak is a result of interference between the anisotropic tensor susceptibility and the magnetic resonant scattering amplitude from 'updowndownup' minor canted moment in ac plane. The noncollinear spin structure is related to the distortion of NiONi bonding to induce nonzero DzyaloshinskiiMoriya interaction, and rather large spinorbit coupling of Ni 3d orbital. 
Tuesday, March 5, 2019 10:24AM  10:36AM 
E07.00013: Correlation between spatial and spectral inhomogeneities in the quasi onedimensional purple bronze Li_{0.9}Mo_{6}O_{17} Samuel Detmer, Anjan Soumyanarayanan, Michael Yee, Yang He, Martha Greenblatt, Nigel Hussey, Jennifer Hoffman The marked deviation from Fermi liquid behavior for the quasionedimensional (1D) purple bronze Li_{0.9}Mo_{6}O_{17} (LMO) has been observed both by bulk transport and by surfacesensitive spectroscopic probes, and has generated much theoretical interest. Here we present spectroscopic scanning tunneling microscope (STM) images of 1D 'chains' on the surface of LMO. We find that the Coulomb suppression of tunneling around the Fermi energy is inhomogenous on the nanometer length scale, which necessitates a revision of the existing model of Luttingerliquidlike behavior that was based on spatiallyaveraged spectroscopic techniques. We further report that chains of varying length exhibit resonances at varying energies, and we discuss the implications of this phenomenon for modeling the surface structure of LMO as a 1D quantum system. 
Tuesday, March 5, 2019 10:36AM  10:48AM 
E07.00014: Slow Dynamics of the Fredkin Spin Chain Khagendra Adhikari, Kevin Beach The dynamical behavior of manyparticle systems is characterized by the lifetime of quasiparticles or excitations. Observables of any nonconserved quantity decay exponentially, but those of a conserved quantity relax to equilibrium with a power law (τ ∼ 1/Δ ∼ L^{z}). Such decay processes are associated with a dynamical exponent (e.g., z = 1 for the ballistic spread of quasiparticles and z = 2 for diffusion) that relates the spread of correlations in space and time. We present numerical results for the Fredkin modela quantum spin chain with an unusual threebody interaction termwhich exhibits a dynamical exponent z ≈ 3. We discuss our efforts to make a reliable, quantitative estimate of z and to explain the very slow dynamics in terms of a random walk executed by the excitation in Monte Carlo time. 
Tuesday, March 5, 2019 10:48AM  11:00AM 
E07.00015: Dynamical spin conductivity in disordered quantum spin chains Shintaro Takayoshi, Thierry Giamarchi Localization caused by disorder has a long history of study since the pioneering work of Anderson. Recently manybody localization (MBL) has been intensively studied in the field of both condensedmatter and statistical physics. Considering the detection of MBL in experiments, it is an important task to investigate on the behavior of physical quantities, especially dynamical ones, in interacting disordered systems. We study the dynamical spin conductivity in XXZ antiferromagnets with random magnetic field. We start from the XX models, which is equivalent to the free fermion system, and then include an Ising interaction. The ground state of easyplane XXZ chains is gapless Luttinger liquid, and the system is localized by disorder when the Luttinger parameter satisfies K<3/2. We calculate dynamical spin conductivity numerically using the technique of Chebyshev matrix product states. We investigate this quantity in the low and high frequency region, and the behavior is power law in both regions. The power depends on the strength of Ising interaction in the high frequency region. 
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