Field-driven quantum phase transitions in S=1/2 spin chains
Sandvik, Anders W.
MetadataShow full item record
Citation (published version)Adam Iaizzi, Kedar Damle, Anders W Sandvik. 2017. "Field-driven quantum phase transitions in S=1/2 spin chains." Physical Review B, Volume 95, Issue 17, 174436. https://doi.org/10.1103/PhysRevB.95.174436
We study the magnetization process of a one-dimensional extended Heisenberg model, the J−Q model, as a function of an external magnetic field h. In this model, J represents the traditional antiferromagnetic Heisenberg exchange and Q is the strength of a competing four-spin interaction. Without external field, this system hosts a twofold-degenerate dimerized (valence-bond solid) state above a critical value qc≈0.85 where q≡Q/J. The dimer order is destroyed and replaced by a partially polarized translationally invariant state at a critical field value. We find magnetization jumps (metamagnetism) between the partially polarized and fully polarized state for q>qmin, where we have calculated qmin=29 exactly. For q>qmin, two magnons (flipped spins on a fully polarized background) attract and form a bound state. Quantum Monte Carlo studies confirm that the bound state corresponds to the first step of an instability leading to a finite magnetization jump for q>qmin. Our results show that neither geometric frustration nor spin anisotropy are necessary conditions for metamagnetism. Working in the two-magnon subspace, we also find evidence pointing to the existence of metamagnetism in the unfrustrated J1−J2 chain (J1>0,J2<0), but only if J2 is spin anisotropic. In addition to the studies at zero temperature, we also investigate quantum-critical scaling near the transition into the fully polarized state for q≤qmin at T>0. While the expected “zero-scale-factor” universality is clearly seen for q=0 and q≪qmin, for q closer to qmin we find that extremely low temperatures are required to observe the asymptotic behavior, due to the influence of the tricritical point at qmin. In the low-energy theory, one can expect the quartic nonlinearity to vanish at qmin and a marginal sixth-order term should govern the scaling, which leads to a crossover at a temperature T∗(q) between logarithmic tricritical scaling and zero-scale-factor universality, with T∗(q)→0 when q→qmin.
Showing items related by title, author, creator and subject.
Rubin, Shanon J.; Xu, Na; Sandvik, Anders W. (American Physical Society, 2017-05-22)We apply a generalized Kibble-Zurek out-of-equilibrium scaling ansatz to simulated annealing when approaching the spin-glass transition at temperature T=0 of the two-dimensional Ising model with random J=±1 couplings. ...
Kara, V.; Yakhot, V.; Ekinci, K. L. (2017-02-17)We explore the scaling behavior of an unsteady flow that is generated by an oscillating body of finite size in a gas. If the gas is gradually rarefied, the Navier-Stokes equations begin to fail and a kinetic description ...
Generation of electric fields and currents by neutral flows in weakly ionized plasmas through collisional dynamos Dimant, Y.S.; Oppenheim, M.M.; Fletcher, A.C. (AMER INST PHYSICS, 2016-08-01)In weakly ionized plasmas neutral flows drag plasma across magnetic field lines generating intense electric fields and currents. An example occurs in the Earth's ionosphere near the geomagnetic equator. Similar processes ...