Spin Supersolid in Anisotropic Spin-One Heisenberg Chain

We consider an S=1 Heisenberg chain with strong exchange (Delta) and single--ion uniaxial anisotropy (D) in a magnetic field (B) along the symmetry axis. The low energy spectrum is described by an effective S=1/2 XXZ model that acts on two different low energy sectors for a given window of fields. The vacuum of each sector exhibits Ising-like antiferromagnetic ordering that coexists with the finite spin stiffness obtained from the exact solution of the effective XXZ model. In this way, we demonstrate the existence of a spin supersolid phase. We also compute the full Delta-B quantum phase diagram by means of a quantum Monte Carlo simulation.Comment: 4+ pages, 2 fig

Antiferromagnetic Order in Pauli Limited Unconventional Superconductors

We develop a theory of the coexistence of superconductivity (SC) and antiferromagnetism (AFM) in CeCoIn5. We show that in Pauli-limited nodal superconductors the nesting of the quasi-particle pockets induced by Zeeman pair-breaking leads to incommensurate AFM with the moment normal to the field. We compute the phase diagram and find a first order transition to the normal state at low temperatures, absence of normal state AFM, and coexistence of SC and AFM at high fields, in agreement with experiments. We also predict the existence of a new double-Q magnetic phase

Vortex Viscosity in Magnetic Superconductors Due to Radiation of Spin Waves

In type-II superconductors that contain a lattice of magnetic moments, vortices polarize the magnetic system inducing additional contributions to the vortex mass, vortex viscosity, and vortex-vortex interaction. Extra magnetic viscosity is caused by radiation of spin waves by a moving vortex. Like in the case of Cherenkov radiation, this effect has a characteristic threshold behavior and the resulting vortex viscosity may be comparable to the well-known Bardeen-Stephen contribution. The threshold behavior leads to an anomaly in the current-voltage characteristics, and a drop in dissipation for a current interval that is determined by the magnetic excitation spectrum.Comment: 4 pages, 1 figur

Electron Spin Resonance of SrCu2(BO3)2 at High Magnetic Field

We calculate the electron spin resonance (ESR) spectra of the quasi-two-dimensional dimer spin liquid SrCu2(BO3)2 as a function of magnetic field B. Using the standard Lanczos method, we solve a Shastry-Sutherland Hamiltonian with additional Dzyaloshinsky-Moriya (DM) terms which are crucial to explain different qualitative aspects of the ESR spectra. In particular, a nearest-neighbor DM interaction with a non-zero D_z component is required to explain the low frequency ESR lines for B || c. This suggests that crystal symmetry is lowered at low temperatures due to a structural phase transition.Comment: 4 pages, 4 b&w figure

Characterization in bi-parameter space of a non-ideal oscillator

The authors thank scientific agencies CAPES, CNPq (112952/2015-1), and FAPESP (2011/ 19269-11). M. S. Baptista also thanks EPSRC (EP/I03 2606/1).Peer reviewedPostprin

The S=1/2 chain in a staggered field: High-energy bound-spinon state and the effects of a discrete lattice

We report an experimental and theoretical study of the antiferromagnetic S=1/2 chain subject to uniform and staggered fields. Using inelastic neutron scattering, we observe a novel bound-spinon state at high energies in the linear chain compound CuCl2 * 2((CD3)2SO). The excitation is explained with a mean-field theory of interacting S=1/2 fermions and arises from the opening of a gap at the Fermi surface due to confining spinon interactions. The mean-field model also describes the wave-vector dependence of the bound-spinon states, particularly in regions where effects of the discrete lattice are important. We calculate the dynamic structure factor using exact diagonalization of finite length chains, obtaining excellent agreement with the experiments.Comment: 16 pages, 7 figures, accepted by Phys. Rev.