Article

# Magnetoacoustics of the Low-Dimensional Quantum Antiferromagnet Cs2CuCl4 with Spin Frustration

Journal of Low Temperature Physics (Impact Factor: 1.18). 01/2010; DOI: 10.1007/s10909-009-0089-3

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**ABSTRACT:**The ground-state ordering and dynamics of the two-dimensional S = 1/2 frustrated Heisenberg antiferromagnet Cs(2)CuCl(4) are explored using neutron scattering in high magnetic fields. We find that the dynamic correlations show a highly dispersive continuum of excited states, characteristic of the resonating valence bond state, arising from pairs of S = 1/2 spinons. Quantum renormalization factors for the excitation energies (1.65) and incommensuration (0.56) are large.Physical Review Letters 03/2001; 86(7):1335-8. · 7.73 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We report magnetization and specific heat measurements in the two-dimensional frustrated spin-1∕2 Heisenberg antiferromagnet Cs2CuCl4 at temperatures down to 0.05 K and high magnetic fields up to 11.5 T applied along a, b, and c axes. The low-field susceptibility χ(T)≃M∕B shows a broad maximum around 2.8 K characteristic of short-range antiferromagnetic correlations and the overall temperature dependence is well described by high temperature series expansion calculations for the partially frustrated triangular lattice with J=4.46 K and J′∕J=1∕3. At much lower temperatures (⩽0.4 K) and in in-plane field (along b and c axes) several new intermediate-field ordered phases are observed in between the low-field incommensurate spiral and the high-field saturated ferromagnetic state. The ground state energy extracted from the magnetization curve shows strong zero-point quantum fluctuations in the ground state at low and intermediate fields.Physical Review B 01/2006; 73(13). · 3.66 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We present a pedagogical overview of recent theoretical work on unconventional quantum phases and quantum phase transitions in condensed matter systems. Strong correlations between electrons can lead to a breakdown of two traditional paradigms of solid state physics: Landau's theories of Fermi liquid and phase transitions. We discuss two resulting “exotic” states of matter: topological and critical spin liquids. These two quantum phases do not display any long-range order even at zero temperature. In each case, we show how a gauge theory description is useful to describe the new concepts of topological order, fractionalization and deconfinement of excitations which can be present in such spin liquids. We make brief connections, when possible, to experiments in which the corresponding physics can be probed. Finally, we review recent work on deconfined quantum critical points. The tone of these lecture notes is expository: focus is on gaining a physical picture and understanding, with technical details kept to a minimum.Physica A: Statistical Mechanics and its Applications 11/2005; · 1.68 Impact Factor

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