arXiv subjects

Satoshi Tanda

Publications and source records attributed to Satoshi Tanda.

30 records · Page 2Linked to original sources

arXiv2016

Chiral Unitary Quantum Phase Transition in 2H-Fe$_x$TaSe$_2$

We have observed a metal-insulator transition of a quasi-two dimensional electronic system in transition metal dichalcogenide $2H$-TaSe$_2$ caused by doping iron. The sheet resistance of $2H$-Fe$_x$TaSe$_2$ ($0 \leq x \leq 0.120$) single crystals rises about $10^6$ times with the increasing of $x$ at the lowest temperature. We investigated the temperature dependence of the resistance and found a metal-insulator transition with a critical sheet resistance $11.7 \pm 5.4$ k$\rmΩ$. The critical exponent of the localization length $ν$ is estimated $0.31 \pm 0.18$. The values of the critical sheet resistance and $ν$ are accordant to those of the \textit{chiral unitary class} (less than $h/1.49e^2=17.3$ k$\rmΩ$ and $0.35 \pm 0.03$, respectively). We suggest that $2H$-Fe$_x$TaSe$_2$ is classified as the chiral unitary class, not as standard unitary class.

cond-mat.mes-hall↗

arXiv2016

Anisotropic magnetoresistance of charge-density wave in $o$-TaS$_3$

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 angle 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.

cond-mat.str-el↗

arXiv2015

Emergence of the Chern structure using Sr$_2$RuO$_4$ nanofilms

We discovered a fractional Chern structure in chiral superconducting Sr$_2$RuO$_4$ nanofilms by employing electric transport. By using Sr$_2$RuO$_4$ single crystals with nanoscale thickness, a fractional Hall conductance was observed without an external magnetic field. The Sr$_2$RuO$_4$ nanofilms enhanced the superconducting transition temperature to about 3 K. We found an anomalous induced voltage with temperature and thickness dependence, and the switching behavior of the induced voltage appeared when we applied a magnetic field. We suggest that there was fractional magnetic-field-induced electric polarization in the interlayer. These anomalous results are related to topological invariance. The fractional axion angle $θ=π/6$ is determined by observing the topological magneto-electric effect in Sr$_2$RuO$_4$ nanofilms.

cond-mat.str-el↗

arXiv2010

Effects of Chern-Simons Corrections on Conserved Quantities of Relativistic Fluid

We consider relativistic fluid flow under Chern-Simons modified Maxwell theory and under Chern-Simons modified gravity theory. We take account of the effects of Chern-Simons corrections on the quantities of fluid flow that are conserved without the Chern-Simons corrections. We find that the conservations of several quantities are generally broken by the Chern-Simons corrections.

gr-qc↗

arXiv2010

Nonlocal transport in the charge density waves of $o$-TaS$_3$

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 its 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.

cond-mat.mtrl-sci↗

arXiv2009

Rotating black hole in extended Chern-Simons modified gravity

We investigate a slowly rotating black hole in four-dimensional extended Chern-Simons modified gravity. We obtain an approximate solution that reduces to the Kerr solution when a coupling constant vanishes. The Chern-Simons correction effectively reduces the frame-dragging effect around a black hole in comparison with that of the Kerr solution.

gr-qc↗

arXiv2009

Aharonov-Bohm Effect at liquid-nitrogen temperature: Frohlich superconducting quantum device

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 the 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.

cond-mat.mes-hall↗

arXiv2009

Discovery of parity-violating Majorana fermions in a chiral superconductor Sr2RuO4

We found parity-violating Majorana fermions in a chiral superconductor Sr2RuO4. The current-voltage curves show an anomalous behavior: The induced voltage is an even function of the bias current. The magnetic field dependent results suggest the excitation of the Majorana fermions along the closed chiral edge current of the single domain under bias current. We also discuss the relationship between a change of the chirality and spontaneous magnetization of the single domain Sr2RuO4.

cond-mat.supr-con↗

arXiv2008

Flat rotation curves in Chern-Simons modified gravity

We investigate the spacetime of a slowly rotating black hole in the Chern-Simons modified gravity. The long range feature of frame-dragging effect under the Chern-Simon gravity well explains the flat rotation curves of galaxies which is a central evidence of dark matter. Our solution provides a different scenario of rotating space from Goedel's solution.

gr-qc↗

arXiv2007

Does a black hole rotate in Chern-Simons modified gravity?

Rotating black hole solutions in the (3+1)-dimensional Chern-Simons modified gravity theory are discussed by taking account of perturbation around the Schwarzschild solution. The zenith-angle dependence of a metric function related to the frame-dragging effect is determined from a constraint equation independently of a choice of the embedding coordinate. We find that at least within the framework of the first-order perturbation method, the black hole cannot rotate for finite black hole mass if the embedding coordinate is taken to be a timelike vector. However, the rotation can be permitted in the limit of $M/r \to 0$ (where $M$ is the black hole mass and $r$ is the radius). For a spacelike vector, the rotation can also be permitted for any value of the black hole mass.

gr-qc↗

arXiv2007

The effect of dissipation on quantum transmission resonance

Quantum transmissions of a free particle passing through a rectangular potential barrier with dissipation are studied using a path decomposition technique. Dissipative processes strongly suppress the transmission probability at resonance just above the barrier resulting in an unexpected reduction of the mean traversal time through the potential barrier.

quant-ph↗

arXiv2006

Topologically Linked Crystals

We discovered a new class of topological crystals, namely linked rings of crystals. Two rings of tantalum triselenide (TaSe3) single crystals were linked to each other while crystal growing. The topology of the crystal form is called a "Hopf link", which is the simplest link involving just two component unknots linked together exactly once. The feature of the crystals is not covered by the conventional crystallography.

cond-mat.mtrl-sci↗