Mila, F., Dorier, J., Schmidt, K. P.
We discuss the appearance of supersolid phases for interacting hardcore bosons on the square lattice when, in addition to the standard nearest neighbor hopping and repulsion, correlated or...
Magnetization plateaux in an extended Shastry-Sutherland model (2008)
Schmidt, K. P., Dorier, J., Mila, F.
We study an extended two-dimensional Shastry-Sutherland model in a magnetic field where besides the usual Heisenberg exchanges of the Shastry-Sutherland model two additional SU(2) invariant couplings...
Perturbative approach to an exactly solved problem: the Kitaev honeycomb model (2008)
Vidal, J., Schmidt, K. P., Dusuel, S.
We analyze the gapped phase of the Kitaev honeycomb model perturbatively in the isolated-dimer limit. Our analysis is based on the continuous unitary transformations method which allows one to...
Mechanisms for Spin-Supersolidity in S=1/2 Spin-Dimer Antiferromagnets (2008)
Albuquerque, A. F., Schmidt, K. P., Laflorencie, N., Troyer, M., Mila, F.
Using perturbative expansions and the contractor renormalization (CORE) algorithm, we obtain effective hard-core bosonic Hamiltonians describing the low-energy physics of $S=1/2$ spin-dimer...
Phase Diagram of the Toric Code Model in a Magnetic Field (2008)
Vidal, J., Dusuel, S., Schmidt, K. P.
We determine the phase diagram of the toric code model in a magnetic field which displays three distinct regions. Our study relies on two high-order perturbative expansions in the strong- and...
Theory of magnetization plateaux in the Shastry-Sutherland model (2008)
Dorier, J., Schmidt, K. P., Mila, F.
Using perturbative continuous unitary transformations, we determine the long-range interactions between triplets in the Shastry-Sutherland model, and we show that an unexpected structure develops at...
Perturbative study of the Kitaev model with spontaneous time-reversal symmetry breaking (2008)
Dusuel, S., Schmidt, K. P., Vidal, J., Zaffino, R. L.
We analyze the Kitaev model on the triangle-honeycomb lattice whose ground state has recently been shown to be a chiral spin liquid. We consider two perturbative expansions: the isolated-dimer limit...
Creation and Manipulation of Anyons in the Kitaev Model (2008)
Dusuel, S., Schmidt, K. P., Vidal, J.
We analyze the effect of local spin operators in the Kitaev model on the honeycomb lattice. We show, in perturbation around the isolated-dimer limit, that they create Abelian anyons together with...
Comment on "Anyonic braiding in optical lattices" (2008)
Vidal, J., Dusuel, S., Schmidt, K. P.
We point out some major technical and conceptual mistakes which invalidate the conclusion drawn in "Anyonic braiding in optical lattices" by C. Zhang, V. W. Scarola, S. Tewari, and S. Das Sarma...
Emergent Fermions and Anyons in the Kitaev Model (2007)
Schmidt, K. P., Dusuel, S., Vidal, J.
We study the gapped phase of the Kitaev model on the honeycomb lattice using perturbative continuous unitary transformations. The effective low-energy Hamiltonian is found to be an extended toric...
We explore the properties of magnetic excitations on the trellis lattice which is relevant for the so-called telephone-number compounds A$_{14}$Cu$_{24}$O$_{41}$ and the system SrCu$_2$O$_3$. The...
One- and Two-Triplon Spectra of a Cuprate Ladder (2006)
Notbohm, S., Ribeiro, P., Lake, B., Tennant, D. A., Schmidt, K. P., Uhrig, G. S., ...
We have performed inelastic neutron scattering on the near ideal spin-ladder compound La4Sr10Cu24O41, which will serve as a model system for the investigation of doped ladders. A key feature in the...
Single-particle versus pair condensation of hard-core bosons with correlated hopping (2006)
Schmidt, K. P., Dorier, J., Laeuchli, A., Mila, F.
We investigate the consequences of correlated hopping on the ground state properties of hard-core bosons on a square lattice as revealed by extensive exact diagonalizations and quantum Monte Carlo...
The fate of orbitons coupled to phonons (2006)
Schmidt, K. P., Grüninger, M., Uhrig, G. S.
The key feature of an orbital wave or orbiton is a significant dispersion, which arises from exchange interactions between orbitals on distinct sites. We study the effect of a coupling between...
Neutron scattering from a coordination polymer quantum paramagnet (2006)
Hong, Tao, Kenzelmann, M., Turnbull, M. M., Landee, C. P., Lewis, B. D., Schmidt, K. P., ...
Inelastic neutron scattering measurements are reported for a powder sample of the spin-1/2 quantum paramagnet $\rm Cu(Quinoxaline)Br_2$. Magnetic neutron scattering is identified above an energy gap...
Schmidt, K. P., Reischl, A., Uhrig, G. S.
In this work we give a consistent picture of the thermodynamic properties of bosons in the Mott insulating phase when loaded adiabatically into one-dimensional optical lattices. We find a crucial...
Temperature in One-Dimensional Bosonic Mott insulators (2005)
Reischl, A., Schmidt, K. P., Uhrig, G. S.
The Mott insulating phase of a one-dimensional bosonic gas trapped in optical lattices is described by a Bose-Hubbard model. A continuous unitary transformation is used to map this model onto an...
Raman Response of Magnetic Excitations in Cuprate Ladders and Planes (2005)
Schmidt, K. P., Gössling, A., Kuhlmann, U., Thomsen, C., Löffert, A., Gross, C., ...
An unified picture for the Raman response of magnetic excitations in cuprate spin-ladder compounds is obtained by comparing calculated two-triplon Raman line-shapes with those of the prototypical...
Magnetic Excitations in Bilayer High-Temperature Superconductors with Stripe Correlations (2005)
Uhrig, G. S., Schmidt, K. P., Grüninger, M.
The universal behaviour of the magnetic excitations in high-temperature superconductors is described in a model with static stripes retaining only the localized spin degrees of freedom. The stripes...
Magnetic excitations in the stripe phase of high-T_c superconductors (2004)
Uhrig, G. S., Schmidt, K. P., Grüninger, M.
The magnetic excitations in the stripe phase of high-T_c superconductors are investigated in a model of spin ladders which are effectively coupled via charged stripes. Starting from the effective...
Unifying Magnons and Triplons in Stripe-Ordered Cuprate Superconductors (2004)
Uhrig, G. S., Schmidt, K. P., Grüninger, M.
Based on a two-dimensional model of coupled two-leg spin ladders, we derive a unified picture of recent neutron scattering data of stripe-ordered La_(15/8)Ba_(1/8)CuO_4, namely of the low-energy...
Rung-singlet phase of the S=1/2 two-leg spin-ladder with four-spin cyclic exchange (2002)
Schmidt, K. P., Monien, H., Uhrig, G. S.
Using continuous unitary transformations (CUT) we calculate the one-triplet gap for the antiferromagnetic S=1/2 two-leg spin ladder with additional four-spin exchange interactions in a high order...
Charge order induced sharp Raman peak in Sr_14Cu_24O_41 (2002)
Schmidt, K. P., Knetter, C., Grüninger, M., Uhrig, G. S.
In the two-leg S=1/2 ladders of Sr_14Cu_24O_41 a modulation of the exchange coupling arises from the charge order within the other structural element, the CuO_2 chains. In general, breaking...
Novel Extrapolation for Strong Coupling Expansions (2002)
Schmidt, K. P., Knetter, C., Uhrig, G. S.
We present a novel extrapolation scheme for high order series expansions. The idea is to express the series, obtained in orders of an external variable, in terms of an internal parameter of the...
Magnetic excitations in two-leg spin 1/2 ladders: experiment and theory (2001)
Grueninger, M., Windt, M., Nunner, T., Knetter, C., Schmidt, K. P., Uhrig, G. S., ...
Magnetic excitations in two-leg S=1/2 ladders are studied both experimentally and theoretically. Experimentally, we report on the reflectivity, the transmission and the optical conductivity...
Optical spectroscopy of (La,Ca)14Cu24O41 spin ladders: comparison of experiment and theory (2001)
Grueninger, M., Windt, M., Nunner, T., Knetter, C., Schmidt, K. P., Uhrig, G. S., ...
Transmission and reflectivity of La_x Ca_14-x Cu_24 O_41 two-leg spin-1/2 ladders were measured in the mid-infrared regime between 500 and 12000 1/cm. This allows us to determine the optical...
Fractional and Integer Excitations in Quantum Antiferromagnetic Spin 1/2 Ladders (2001)
Knetter, C., Schmidt, K. P., Grüninger, M., Uhrig, G. S.
Spectral densities are computed in unprecedented detail for quantum antiferromagnetic spin 1/2 two-leg ladders. These results were obtained due to a major methodical advance achieved by optimally...
Verfahren zum mikrobiellen Abbau von Leder (1996)
Kuemmel, R., Merrettig-Bruns, U., Knappertsbusch, V., Wiehn, H., Schmidt, K.P.
DE 4422246 C UPAB: 19960227 Method for the degradation of leather, esp. untreated, tanned and/or finished leather prods. or waste, comprises treating the opt. pre-crushed leather material in a...