Novel quantum state on the verge of destruction of the lower charge-density-wave phase in NbSe 3

Abstract

We report the results of the resistance ( R) and magnetoresistance (MR) measurements in NbSe 3 near the critical pressure ( P c), where the lower charge-density-wave (CDW) phase is on the verge of destruction. Near P c, the temperature dependence of d R/d T exhibits a weak anomaly at T ∗=15 K. MR gradually increases with decreasing temperature down to T ∗, and then rises sharply below T ∗. Comparing this sharp rise in MR with the large magnetoresistance (LMR) in the lower CDW phase reported previously, we find that there exists the lower CDW phase below T ∗. However, MR does not follow Kohler's rule even at T< T ∗/2, where the temperature dependence of the CDW gap is very little. Moreover, detailed analysis of the temperature dependence of R and d R/d T show that the weak anomaly of d R/d T at T ∗ yields an excess conductance below T ∗ in spite of the formation of the CDW gap. The violation of Kohler's rule and the excess conductance below T ∗ are discussed in terms of the quantum fluctuation of the CDW phase near P c.