We report the magnetoresistance of a charge-density wave (CDW) in $o$-TaS$_3$ whiskers at 4.2 K under a magnetic field up to 5.2 T. An anisotropic negative magnetoresistance is found in the nonlinear regime of current-voltage characteristics. The ang
le dependence of the magnetoresistance, studied by rotating the magnetic field upon the $c$-axis, exhibited a two-fold symmetry. The magnetoresistance amplitude exhibits maxima when the field is parallel to the $a$-axis, whereas it vanishes to the $b$-axis. The observed anisotropy may come from difference in interchain coupling of adjacent CDWs along the $a$- and $b$-axes. Comparison of the anisotropy to the scanning tunneling microscope image of CDWs allows us to provide a simple picture to explain the magnetoresistance in terms of delocalization of quantum interference of CDWs extending over the $b$-$c$ plane.
We studied the nonlocal transport of a quasi-one dimensional conductor $o$-TaS$_3$. Electric transport phenomena in charge density waves include the thermally-excited quasiparticles, and collective motion of charge density waves (CDW). In spite of it
s long-range correlation, the collective motion of a CDW does not extend far beyond the electrodes, where phase slippage breaks the correlation. We found that nonlocal voltages appeared in the CDW of $o$-TaS$_3$, both below and above the threshold field for CDW sliding. The temperature dependence of the nonlocal voltage suggests that the observed nonlocal voltage originates from the CDW even below the threshold field. Moreover, our observation of nonlocal voltages in both the pinned and sliding states reveals the existence of a carrier with long-range correlation, in addition to sliding CDWs and thermally-excited quasiparticles.
The Aharonov-Bohm (AB) effect has been accepted and has promoted interdisciplinary scientific activities in modern physics. To observe the AB effect in condensed matter physics, the whole system needs to maintain phase coherence, in a tiny ring of th
e diameter 1 micrometer and at low temperatures below 1 K. We report that AB oscillations have been measured at high temperature 79 K by use of charge-density wave (CDW) loops in TaS3 ring crystals. CDW condensate maintained macroscopic quantum coherence, which extended over the ring circumference 85 micrometer. The periodicity of the oscillations is h/2e in accuracy within a 10 percent range. The observation of the CDW AB effect implies Frohlich superconductivity in terms of macroscopic coherence and will provide a novel quantum interference device running at room temperature.
