Magnetic-field-induced phase transition and sliding motion of charge-density waves in η-Mo4O11

Abstract

Transverse magnetoresistance and Hall effect of the charge-density-wave ͑CDW͒ material -Mo 4 O 11 have been measured at 4.2 K ͑second CDW state͒ by dc and ac methods over the frequency range 50-500 kHz in pulsed magnetic fields up to 40 T. These quantities are both reversible and frequency independent for a low-field sweep up to near 10 T ͑ϭH c ͒, beyond which an appreciable frequency-dependent hysteresis effect appears. The Cole-Cole plots of the real versus imaginary parts of the magnetoresistance at high magnetic fields show a monodispersion. The magnetic-field dependence of the real part of the ac Hall resistivity shows interesting behaviors, peaking near H c , followed by a decrease with H and a leveling off at high fields, while the imaginary components are very small and less frequency dependent. Using a multicarrier model consisting of the remaining and nested electron and hole bands, we have performed computer simulations for these dc and ac magnetotransport quantities, in satisfactory agreement with the observations. We have taken into account ͑1͒ the Zeeman effect for two types of the remaining hole and electron bands, ͑2͒ the CDW-gap narrowing of the nested electron and hole bands, ͑3͒ magnetic-field-induced CDW-to-normal phase transition in part of these nested bands, and ͑4͒ the magnetic-field-induced ''CDW oscillation'' around some mean position of the CDW condensates ͑or thermal excitation of the CDW phasons over a pinning potential͒, according to the existing CDW model.