Effect of pressure on the quantum spin ladder material IPA-CuCl3
  Inelastic neutron scattering and bulk magnetic susceptibility studies of the quantum S=1/2 spin ladder system IPA-CuCl3 are performed under hydrostatic pressure. The pressure dependence of the spin gap $\Delta$ is determined. At $P=1.5$ GPa it is reduced to $\Delta=0.79$ meV from $\Delta=1.17$ meV at ambient pressure. The results allow us to predict a soft-mode quantum phase transition in this system at P$_\mathrm{c}\sim 4$ GPa. The measurements are complicated by a proximity of a structural phase transition that leads to a deterioration of the sample. 
Tao Hong, V. O. Garlea, A. Zheludev, J. Fernandez-Baca, H. Manaka, S.   Chang, J. B. Leao, and S. J. Poulton