Erik Wulf

Criticality in a disordered quantum antiferromagnet studied by neutron diffraction

E. Wulf, D. Hüvonen, J.-W. Kim, 3 A. Paduan-Filho, E. Ressouche, S. Gvasaliya, V. Zapf, and A. Zheludev ∗ Neutron Scattering and Magnetism, Laboratory for Solid State Physics, ETH Zürich, Zürich, Switzerland. National High Magnetic Field Laboratory, MPA-CMMS group, Los Alamos National Lab (LANL), Los Alamos, NM 87545, USA. Lujan Center for Neutron Scattering, LANL, Los Alamos, NM 87545, USA. High Magnetic Field Laboratory, University of São Paulo, 05315-970, São Paulo, Brazil. INAC/SPSMS-MDN, CEA/Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France. (Dated: October 4, 2013)

Crystals for neutron scattering studies of quantum magnetism

We review a strategy for targeted synthesis of large single crystal samples of prototype quantum magnets for inelastic neutron scattering experiments. Four case studies of organic copper halogenide S = 1/2 systems are presented. They are meant to illustrate that exciting experimental results pertaining to the forefront of many-body quantum physics can be obtained on samples grown using very simple techniques, standard laboratory equipment, and almost no experience in advanced crystal growth techniques.

Disorder instability of the magnon condensate in a frustrated spin ladder

The effect of disorder is studied on the field-induced quantum phase transition in the frustrated spin-ladder compound H8C4SO2Cu2(Cl[1-x]Brx)4 using bulk magnetic and thermodynamic measurements. The parent material (x=0) is a quantum spin liquid, which in applied fields is known to form a magnon condensate with long-range helimagnetic order. We show that bond randomness introduced by a chemical substitution on the non-magnetic halogene site destroys this phase transition at very low concentrations, already for x=0.01. The extreme fragility of the magnon condensate is attributed to random frustration in the incommensurate state.

Quantum criticality in a three-dimensional spin system at zero field and pressure

We report on the spontaneous appearance of antiferromagnetic order in a model gapped quantum paramagnet

Giant dielectric nonlinearities at a magnetic Bose-Einstein condensation

\mathrm{Ni}{({\mathrm{Cl}}_{1\ensuremath{-}x}{\mathrm{Br}}_{x})}_{2}\ifmmode\cdot\else\textperiodcentered\fi{}4\mathrm{SC}{({\mathrm{NH}}_{2})}_{2}

Dynamics of a bond-disordered S = 1 quantum magnet near z = 1 criticality

induced by a change in bromine concentration

Quantum Criticality in a Strongly Coupled S =1 Spin Chain System at Ambient Field and Pressure

x

Dielectric effects at a magnetic Bose-Einstein condensation

. This transition is qualitatively similar to a

Neutron scattering studies of a bond-disordered

z=1

S=1

magnetic quantum critical point. However, the observed critical scaling of thermodynamic and magnetic properties has rather unusual critical exponents.