S. Sahling

Interplay between phase defects and spin polarization in the specific heat of the spin-density-wave compound (TMTTF)2Br in a magnetic field.

Equilibrium heat relaxation experiments provide evidence that the ground state of the commensurate spin-density-wave compound (TMTTF)2Br after the application of a sufficient magnetic field is different from the conventional ground state. The experiments are interpreted on the basis of the local model of strong pinning as the deconfinement of soliton-antisoliton pairs triggered by the Zeeman coupling to spin degrees of freedom, resulting in a magnetic-field-induced density-wave glass for the spin carrying the phase configuration.

Spin dynamics in the presence of competing ferromagnetic and antiferromagnetic correlations in Yb2Ti2O7

In this work, we show that the zero field excitation spectra in the quantum spin ice candidate pyrochlore compound \ybti\ is a continuum characterized by a very broad and almost flat dynamical response which extends up to

Relaxation time spectrum of low-energy excitations in one- and two-dimensional materials with charge or spin density waves

1-1.5

Heat capacity of the 1D SDW system (TMTTF)2Br and 2D CDW system 1T-TaS2 in magnetic field

meV, coexisting or not with a quasi-elastic response depending on the wave-vector. The spectra do not evolve between 50 mK and 2 K, indicating that the spin dynamics is only little affected by the temperature in both the short-range correlated and ordered regimes. Although classical spin dynamics simulations qualitatively capture some of the experimental observations, we show that they fail to reproduce this broad continuum. In particular, the simulations predict an energy scale twice smaller than the experimental observations. This analysis is based on a careful determination of the exchange couplings, able to reproduce both the zero field diffuse scattering and the spin wave spectrum rising in the field polarized state. According to this analysis, \ybti\ lies at the border between a ferro and an antiferromagnetic phase. These results suggest that the unconventional ground state of \ybti\ is governed by strong quantum fluctuations arising from the competition between those phases. The observed spectra may correspond to a continuum of deconfined spinons as expected in quantum spin liquids.

Magnetic field influence on the low-temperature heat capacity of the CDW compounds TaS

The long-time thermal relaxation of (TMTTF)

_{3}

_2

and Rb

Br, Sr

_{0.3}

_{14}

MoO

Cu

_{3}

_{24}