Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session A12: Strongly Correlated 1D Systems 
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Sponsoring Units: DCMP Chair: Gregory Fiete, California Institute of Technology Room: Morial Convention Center 203 
Monday, March 10, 2008 8:00AM  8:12AM 
A12.00001: Local density of states in Luttinger liquids with a dynamicallygenerated spin gap Dirk Schuricht, Akbar Jaefari, Fabian Essler, Eduardo Fradkin We present a theory of STM spectroscopy in semiinfinite 1D strongly correlated electron systems with a spingap. We calculate the local density of states of semiinfinite Luttinger liquids with open boundary conditions and a dynamically generated spin gap at zero temperature. In order to perform this calculation, we use the boundary state formalism [1] together with a form factor expansion in the infinite system. We find explicit expressions for the local density of states as a function of the gap size and the distance from the boundary. We show how a local spectroscopic probe of this type can be used a)to detect the spectrum of fractionalized massive solitons and their dynamics, b)the existence of boundary states and c)charge order induced by the boundary. We will discuss the relevance of this work to STM experiments in 1D systems and in quasi1D systems used to model stripe phases in strongly correlated systems [2]. [1] S. Ghoshal and A. Zamolodchikov, Int. J. Mod. Phys. 9, 3841(1994), ibid. 9, E4353(1994). [2] S. A. Kivelson, I. P. Bindloss, E. Fradkin, V. Oganesyan, J. Tranquada, A. Kapitulnik and C. Howald, Rev. Mod. Phys. 75, 1201(2003). [Preview Abstract] 
Monday, March 10, 2008 8:12AM  8:24AM 
A12.00002: SpinIncoherent Luttinger LiquidSuperconductor Hybrid Systems Dagim Tilahun, Gregory Fiete Strongly interacting onedimensional systems exhibit the exotic property of {\em spincharge separation} where a repulsive interaction suppresses the velocity of the spin degree of freedom while enhancing that of the charge. Spinincoherent Luttinger liquids exist in the regime where the temperature is much higher than the characteristic energy of the spin sector (thermalized, random spins) but much less than that of the charge. We study a hybrid system consisting of a spinincoherent Luttinger liquid adjoined at one or both ends to a superconductor, and find robust features that can be used as clear experimental signatures of spinincoherence. We find the tunneling density of states diverges at low energies and exhibits a universal frequency dependence independent of the strength of the interactions in the system. We also find that in spite of exponentially decaying pair correlations with distance into the spinincoherent Luttinger liquid, the Josephson current remains robust. Compared to the zero temperature Luttinger liquid case there is a factor of 2 reduction in the critical current and a halving of the period in the phase difference between the superconductors. Our results open the way for a new class of experiments in the spinincoherent regime of one dimensional systems. [Preview Abstract] 
Monday, March 10, 2008 8:24AM  8:36AM 
A12.00003: Temperature dependence of the anomalous exponent in Li(0.9)Mo(6)O(17) that reveals Luttinger Liquid behavior Rene Matzdorf, Tatjana Novgorodov, Bernard Nansseu, Michael Waelsch, Jian He, Rongying Jin, David Mandrus Scanning tunneling spectroscopy (STS) has been used to study the Luttingerliquid behavior of the purple bronze Li(0.9)Mo(6)O(17) in the temperature range 5K < T < 300K. In the entire temperature range the suppression of density of states at the Fermienergy could be fitted very good by a model describing the tunneling into a Luttinger liquid at ambient temperature. The powerlaw exponent extracted from these fits reveals a significant increase above 200K. It changes from $\alpha$=0.6 at low temperature to $\alpha$=1.0 at room temperature. [Preview Abstract] 
Monday, March 10, 2008 8:36AM  8:48AM 
A12.00004: Specific heat of a onedimensional interacting Fermi system Andrey Chubukov, Dmitrr Maslov, Ronojoy Saha We revisit the issue of the temperature dependence of the specific heat $% C(T)$ for interacting fermions in 1D. The charge component $C_c (T)$ scales linearly with $T$, but the spin component $C_s (T)$ displays a more complex behavior with $T$ as it depends on the backscattering amplitude, $g_1$, which scales down under RG transformation and eventually behaves as $g_1 (T) \sim 1/\log T$. We show, however, by direct perturbative calculations that $C_s (T)$ is strictly linear in $T$ to order $g^2_1$ as it contains the renormalized backscattering amplitude not on the scale of $T$, but at the cutoff scale set by the momentum dependence of the interaction around $2k_F$. The running amplitude $g_1 (T)$ appears only at third order and gives rise to an extra $T/\log^3 T$ term in $C_s (T)$. This agrees with the results obtained by a variety of bosonization techniques. We also show how to obtain the same expansion in $g_1$ within the sineGordon model. [Preview Abstract] 
Monday, March 10, 2008 8:48AM  9:00AM 
A12.00005: Entanglement and quantum phase transition in the ground state of onedimensional asymmetric Hubbard model Wenling Chan, ShiJian Gu We study the quantum phase transition by means of entanglement in the ground state of the onedimensional asymmetric Hubbard model. Both the halffilling and away from halffilling cases are investigated. The local entanglement between the middle two sites with the rest of the system, and the block entanglement between the left and right portions of the system, are calculated by the DMRG method. We find that the entanglements show interesting scaling and singular behavior around the phase transition line. [Preview Abstract] 
Monday, March 10, 2008 9:00AM  9:12AM 
A12.00006: Is the Drude weight a thermodynamic quantity? Marcos Rigol, B. Sriram Shastry Transport properties distinguish metals from insulators, and superconductors from ideal metals. In one dimension, they can help differentiate integrable from nonintegrable systems. The Drude weight (or charge stiffness) is found to be nonzero in integrable metals, even at very large temperature, whereas it vanishes for generic (nonintegrable) systems. In systems with periodic boundary conditions, the Drude weight can be identified as the coefficient accompanying the zerofrequency delta peak in the real part of the electrical conductivity. Paradoxically on the other hand, for systems with open boundary conditions, it can be shown that this coefficient is identically zero for any finite system, regardless of its integrability. For the Drude weight to be a thermodynamically meaningful quantity, both kinds of boundary conditions should produce the same answer in the thermodynamic limit. We resolve this paradox using analytical and numerical methods. [Preview Abstract] 
Monday, March 10, 2008 9:12AM  9:24AM 
A12.00007: Phase diagram of hole doped twoleg $Cu$$O$ ladders Piotr Chudzinski, Marc Gabay, Thierry Giamarchi In the weak coupling limit, we establish the phase diagram of a twoleg ladder with a unit cell containing both $Cu$ and $O$ atoms, as a function of doping. We use bosonization and design a specific RG procedure to handle the additional degrees of freedom. Significant differences are found with the single orbital case; for purely repulsive interactions, a completely massless quantum critical region is obtained at intermediate carrier concentrations(well inside the bands). For some finite value of direct hopping between oxygen atoms the ground state consists of an incommensurate pattern of orbital currents plus a spin or charge density wave (DW) structure. The experimental relevance of these findings is also discussed. We have calculated the NMR properties like Knight shift and relaxation rate at each atom inside the elementary cell. We make a prediction that different temperature dependance indicates the phase of the measured system. [Preview Abstract] 
Monday, March 10, 2008 9:24AM  9:36AM 
A12.00008: Groundstate fidelity and the spin one chain Ian McCulloch it has been recognized quite recently that the groundstate fidelity, that is, the overlap of the groundstate wavefunctions as a function of interaction strength, can be used to obtain phase boundaries and exponents \emph{without} apriori knowledge of the order parameter. This procedure is easy to apply in a wide class of numerical algorithms based on matrix product states, of which the Density Matrix Renormalization Group (DMRG) is the most famous. I will give a brief overview of the technique, and demonstrate that the fidelity reveals \emph{all} features of the bilinearbiquadratic spin one chain, while almost certainly ruling out the appearance of a (gapped or critical) nematic phase in the vicinity of $\theta = 3\pi / 4$. [Preview Abstract] 
Monday, March 10, 2008 9:36AM  9:48AM 
A12.00009: Magnetism of onedimensional Wigner lattices and its impact on charge order Maria Daghofer, Reinhard Noack, Peter Horsch We report the phase diagram of a quarterfilled Wigner lattice described by the 1D HubbardWigner model with nearest and nextnearest neighbor hopping $t_1$ and $t_2$. In the $t_1$$t_2$ plane, we find a region at negative $t_2$ with fully saturated ferromagnetic ground states due to kinetic exchange interactions, while the remaining phase diagram is controlled by antiferromagnetic exchange. We also observe a strong influence of magnetism on the charge structure factor, in contrast to the expectation that charge ordering in the Wigner lattice is well described by spinless fermions. Our results, obtained using the densitymatrix renormalization group and exact diagonalization, can be transparently explained within the framework of an effective lowenergy Hamiltonian. [Preview Abstract] 
Monday, March 10, 2008 9:48AM  10:00AM 
A12.00010: Critical lines and massive phases in quantum spin ladders with dimerization Javier Almeida, Miguel Angel MatinDelgado, German Sierra We study here various types of S=1/2 spin ladders with odd and even number of legs and intrinsically dimerized patterns. The low temperature physics of these systems is very rich and in fact their ground state at T=0 may undergo a quantum phase transition as we vary the microscopic parameters of the lattices. To study these manybody systems we will use the density matrix renormalization group (DMRG) algorithm, and will present accurate estimations of the critical lines found in these models as well as different measurements to characterize the nature of the ground state. We will see that the valence bond solid picture seems to be a proper description of the massive phases on each side of the phase diagram and will show evidences of this nature by means of a particular order parameter denoted generalized string order parameter. [Preview Abstract] 

A12.00011: ABSTRACT WITHDRAWN 
Monday, March 10, 2008 10:12AM  10:24AM 
A12.00012: Magnetostriction and thermal expansion on 1D chain compound Azurite Frederik W. Fabris, Vivien Zapf, Sonia Francoual, Marcelo Jaime, Alex Lacerda Azurite is a natural mineral with a chemical structure Cu$_{3}$(OH$_{2})$(CO$_{3})_{2}$. This compound is a frustrated triangular quantum magnet consisting of Cu S=1/2 atoms arranged alternately to form infinite chains along the b axis. The magnetic behavior of this compound reflects the existence of both monomers and dimers of S = 1/2 Cu. A magnetization plateau at 1/3 of the saturization magnetization is observed in M vs H measurements between 11 and 30 T due to saturization of the monomers. For fields above the plateau, the magnetic field energy exceeds the dimer bonding and thus the dimers cant and then align with the field. The magnetic structure and the detailed phase diagram in temperature and field are largely unknown or controversial. A recent report [1] in the specific heat behavior suggests a more complicated structure than previously thought. In addition, recent ultrasound measurements [2] indicate significant magnetoelastic coupling must be taken into account. We have acquired interesting results on magnetic torque, magnetostriction and thermal expansion. We have demonstrated that significant, anisotropic magnetostriction occurs in azurite, giving us an indication of the magnetically induced structural distortions. [1] Yasu Takano, personal communication. [2] Lang et al, J. Phys.: Conf. Series 51, 1, (2006). [Preview Abstract] 
Monday, March 10, 2008 10:24AM  10:36AM 
A12.00013: Quantum Monte Carlo study of a spinPeierls model in a magnetic field Jeongpil Song, R.T. Clay We present results of a quantum Monte Carlo study of a quasi onedimensional XY spin model coupled to quantum phonons. We compare different updating techniques for the Stochastic Series Expansion method and present autocorrelation time data. We are able to reduce autocorrelation times by using loop update techniques for both spin and phonon degrees of freedom. We determine the critical phonon coupling for the spinPeierls state, and discuss the dependence on the phonon frequency, magnetic field, and interchain coupling. [Preview Abstract] 
Monday, March 10, 2008 10:36AM  10:48AM 
A12.00014: Quantum solvation in optical lattice You Wenlong, Gu Shijian, Lin Haiqing We have studied the ground state phase diagram of the one dimensional asymmetric tJJz model at various filling by different methods. The reduced dimensionality and asymmetric hopping could lead to interesting dynamics which can be conjectured to demonstrate quantum solvation process with fermion character of the quantum solvent. The system potentially can be demonstrated in optical lattice. [Preview Abstract] 
Monday, March 10, 2008 10:48AM  11:00AM 
A12.00015: Effective model parameters for the spinPeierls system TiOCl from first principles Yuzhong Zhang, Roser Valenti, Harald Jeschke The inorganic spinPeierls system TiOCl is studied in the frame of Density Functional Theory (DFT) by the projector augmented wave (PAW) and linearized augmented plane wave (LAPW) methods. A twodimensional frustrated spin Peierls model is proposed to describe the system. The model parameters, such as spin exchange couplings in a, b, and c directions, are estimated by the LAPW method. With the help of the eigenvectors of the dynamical matrix, the spinphonon couplings and the elastic constant are determined by the PAW method. The reliability of these model parameters is demonstrated by an exact diagonalization and a meanfield calculation as well as by comparison to available experiments. [Preview Abstract] 
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