Stress dependence of the charge-density-wave transitions in NbSe3 and TaS3

We have measured the change in the charge-density-wave (CDW) transitions in monoclinic NbSe3 and orthorhombic TaS3 caused by stress applied along the high-symmetry (growth) axis. For the upper transition in NbSe3, dT1d=-4.4 K/GPa for stresses up to 5 GPa, the increase in the resistance due to the transition, R, is almost unaffected, and the critical field for motion of the CDW, Ec, increases with stress. For the lower transition in NbSe3, dT2d=-0.4 K/GPa, R more than doubles at 5 GPa, and Ec is relatively unaffected. The 222-K transition in TaS3 decreases at a rate of -15 K/GPa for low stresses. At stresses above 2.5 GPa the resistance of TaS3 begins to increase again, possibly due to a second stress-induced CDW transition. Both thermal hysteresis and stress hysteresis are seen in TaS3 between about 100 and 200 K.