arXiv subjects

Toru Matsuura

Publications and source records attributed to Toru Matsuura.

4 recordsLinked to original sources

arXiv2024

Efficiency of negative-illumination photovoltaic energy conversion

Infrared diodes generate electricity from thermal radiation emitted from themselves. The negative process of photovoltaic effect has been expected for application to energy harvesting systems converting from terrestrial radiation. However, its energy conversion efficiency has been known to be very low. In this paper, we investigate energy conversion efficiency and external quantum efficiency for the negative-illumination photovoltaic effect with a systematic measurement for infrared diodes faced to a sufficiently cold surface. We find that the external quantum efficiency reaches 60\ \% for a diode at a temperature, while the energy conversion efficiency stays below 10^-4 %. We indicate dominant parameters for the efficiencies and propose how to improve energy conversion efficiency.

physics.app-ph↗

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↗

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↗