Control of the electron spectrum of a quasi-one-dimensional conductor K0.3MoO3 with the use of a microcontact

When an electric field is applied to a Peierls quasi-one-dimensional conductor K_0.3MoO₃, a change in conductivity is observed in the vicinity of the point contact. This change is due to a strong local distortion of the charge density wave in the pinned state. In this case, the chemical potential can be varied over a wide range by changing the conductivity from the n type to the p type. The local position of the chemical potential can be determined by the method proposed; in particular, the low-temperature anomaly of conductivity is explained.     

Formal Mott transition between the one dimensional conductor K0.3MoO3 and the highly anisotropic semiconductor K0.33MoO3

The blue bronze K_0.3MoO₃ (1) is well known to have a 1-D character along the crystallographic b axis. The red bronze K_0.33MoO₃, instead, is a semiconductor with a 0.5 eV energy gap (2). The two bronzes have a different crystallographic configuration. In a microscopic model one can derive the red bronze structure from the one of the blue bronze and one can explain the metal semiconductor “transition” between K_0.3MoO₃ and K_0.33MoO₃ with a formal Mott transition of delocalized into localized states due to a critical overlap between cationanion-cation orbitals.     

Thermal conductivity of K0.3MoO3

Measurements of thermal conductivity of the blue bronze K_0.3MoO₃ are reported in the range 90–300K. A large anomaly at 183 K ascribed to the CDW transition and an overall good agreement of the experimental results with the estimations based on the Wiedemann-Franz are found.     

Intermittent impulsive oscillations in K0.3MoO3

The undamped oscillations observed just above the switching threshold was investigated in K_0.3MoO₃. Each oscillation is impulsive, and possibly represents the elementary process of the motion of the charge density waves (CDW's). Furthermore, intermittency is found in these impulsive oscillations, which is comfirmed to be the direct origin of the low-frequency broadband noise. The analysis of the noise indicates that the degree of freedom of the motion is almost unity which means that the motion of the CDW's is spatially coherent.     

Local spectroscopy of carrier reflection at the interface between a normal metal and the Peierls conductor K0.3MoO3

The nature of carrier reflection from a normal metal-Peierls conductor interface is clarified by studying the characteristics of point contacts formed with an intermediate metallic layer sputtered onto the (010) face of K_0.3MoO₃ crystals (injection along the chains) or the face (injection perpendicular to the chains). In the Peierls state, for bias voltages eV smaller than the Peierls gap Δ_P, an excess differential resistance is observed with a local minimum at V=0. The magnitude of the excess resistance is proportional to a ²/d ², where a is the contact diameter and d is the thickness of the metal film. The excess resistance is much higher for injection along the chains than for injection perpendicular to them. A comparative analysis of the data for different injection directions indicates that the dominant contribution to the excess resistance for injection along the chains is from normal reflection of carriers without changes in the sign of their charge and with a momentum transfer 2p _F to the condensate of electron-hole pairs carried away from the interface. Zh. éksp. Teor. Fiz. 113, 1830–1842 (May 1998)     

Size effects on the charge-density-wave pinning in the quasi-one-dimensional conductor K0.30MoO3

We report size effects on the charge-density-wave pinning in the quasi-one-dimensional conductor K_0.30MoO₃ in the temperature range 77 K-160 K. The threshold field is approximately one order of magnitude larger in needle-like samples than in bulk crystals, temperature independent and strongly dependent on the width of the sample. In addition, the nonlinear conductivity shows a maximum near 130 K. The results are discussed in relation with various pinning models and CDW dislocations.     

电荷密度波材料K0.3MoO3及W掺杂样品的红外光学响应的研究

研究了准一维材料K03MoO3以及掺杂了3%和15%的W的样品在TCDW=180K以上和以下的温度时的光反射谱和电导率谱.在此基础上讨论了伴随着Peierls相变产生的相声子和单粒子能隙,以及W掺杂对CDW凝聚的影响 关键词： 电荷密度波 Peierls相变     

Metastable state of sliding CDW in K0.3MoO3

The narrow band noise and the transient voltage oscillation were investigated in a k_0.3MoO₃ sample, which showed different I–V characteristics in the non-linear conductivity region for dc and pulse methods. For repeated current pulses, after a sufficiently long duration of dc current, the voltage response showed relaxation behavior with a relaxation time of about 30 min at 77 K. Similar relaxation was also observed for the opposite case of a dc current applied after repeated pulses. The slope of frequency of voltage oscillation against CDW current was constant through these relaxation process in both dc and pulse cases. But the peak of narrow band noise is larger and sharper after repeated pulses than in the dc stationary state. This result was understood as an enhancement of the coherent-phase region for voltage oscillation in the case of repeated pulses.