We present a flexible density-matrix renormalization group approach to calculate finite-temperature spectral functions of one-dimensional strongly correlated quantum systems. The method combines the purification of the finite-temperature density operator with a moment expansion of the Green's function. Using this approach, we study finite-temperature properties of dynamical spectral functions of spin- $1/2$ XXZ chains with Dzyaloshinskii-Moriya interactions in magnetic fields and analyze the effect of these symmetry breaking interactions on the nature of the finite-temperature dynamic spin structure factor.We present a flexible density-matrix renormalization group approach to calculate finite-temperature spectral functions of one-dimensional strongly correlated quantum systems. The method combines the purification of the finite-temperature density operator with a moment expansion of the Green's function. Using this approach, we study finite-temperature properties of dynamical spectral functions of spin-$1/2$ XXZ chains with Dzyaloshinskii-Moriya interactions in magnetic fields and analyze the effect of these symmetry breaking interactions on the nature of the finite-temperature dynamic spin structure factor.

arXiv:1312.6044Physical Review BAug 21, 201442 citations

Finite temperature dynamics of the spin-half Heisenberg chain

Oleg A. Starykh, Anders W. Sandvik, Rajiv R. P. Singh

Physica B Condensed MatterDec 1, 19974 citations

Solitons in ferromagnetic spin-1 chains?

T. Schneider, E. Stoll

We report finite-ring calculations revealing that spin-1 ferromagnetic easy-plane chains in a symmetry-breaking field are well described by a weakly interacting Bose gas. The thermally-induced central peak (CP) previously observed by neutron scattering from CsNiF3, and interpreted in terms of solitons, is traced back to annihilation/creation processes of the excitations. Its temperature variation shows a pronounced interaction-mediated saturation. The essential features of the spin dynamics and of the field and temperature dependence of the specific heat can be explained without solitons. We predict corresponding CP phenomena in a large variety of spin systems.We report finite-ring calculations revealing that spin-1 ferromagnetic easy-plane chains in a symmetry-breaking field are well described by a weakly interacting Bose gas. The thermally-induced central peak (CP) previously observed by neutron scattering from CsNiF3, and interpreted in terms of solitons, is traced back to annihilation/creation processes of the excitations. Its temperature variation shows a pronounced interaction-mediated saturation. The essential features of the spin dynamics and of the field and temperature dependence of the specific heat can be explained without solitons. We predict corresponding CP phenomena in a large variety of spin systems.

Journal of Applied PhysicsNov 1, 198211 citations

Dynamical correlations of spin-1/2 chains

Rodrigo G. Pereira, Steven White, Ian K. Affleck

Bulletin of the American Physical SocietyMar 12, 20080 citations

Interacting spins in a cavity: Finite-size effects and symmetry-breaking dynamics

Søren Gammelmark, Klaus Mølmer

We calculate the ground state and simulate the dynamics of a finite chain of spins with Ising nearest-neighbor interactions and a Dicke collective spin interaction with a single-mode cavity field. We recover the signatures of first- and second-order phase transitions predicted by mean-field theory, and for small chains, we find significant and nontrivial finite-size effects. Below the first-order phase transition, even quite large spin chains of 30--40 spins give rise to a mean photon number and number fluctuations significantly above the mean-field vacuum result. Near the second-order phase critical point, our calculations reveal photon number fluctuations that grow beyond Poisson statistics with the size of the spin chain. We simulate the stochastic evolution of the system when the cavity output field is subject to homodyne detection. For an initial state close to the first-order phase-transition the random character of the measurement process causes a measurement-induced symmetry breaking in the system. This symmetry breaking occurs on the time scale needed for an observer to gather sufficient information to distinguish between the two possible (mean-field) symmetry-broken states.We calculate the ground state and simulate the dynamics of a finite chain of spins with Ising nearest-neighbor interactions and a Dicke collective spin interaction with a single-mode cavity field. We recover the signatures of first- and second-order phase transitions predicted by mean-field theory, and for small chains, we find significant and nontrivial finite-size effects. Below the first-order phase transition, even quite large spin chains of 30--40 spins give rise to a mean photon number and number fluctuations significantly above the mean-field vacuum result. Near the second-order phase critical point, our calculations reveal photon number fluctuations that grow beyond Poisson statistics with the size of the spin chain. We simulate the stochastic evolution of the system when the cavity output field is subject to homodyne detection. For an initial state close to the first-order phase-transition the random character of the measurement process causes a measurement-induced symmetry breaking in the system. This symmetry breaking occurs on the time scale needed for an observer to gather sufficient information to distinguish between the two possible (mean-field) symmetry-broken states.

arXiv:1202.5397Physical Review AApr 25, 201220 citations

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XXZ chains with Dzyaloshinskii-Moriya interactions in magnetic fields and analyze the effect of these symmetry breaking interactions on the nature of the finite-temperature dynamic spin structure factor.