arXiv subjects

Jae-Hyuk Choi

Publications and source records attributed to Jae-Hyuk Choi.

5 recordsLinked to original sources

arXiv2017

Precision determination of a fluxoid quantum's magnetic moment in a superconducting micro-ring

Using dynamic cantilever magnetometry and experimentally determining the cantilever's vibrational mode shape, we precisely measured the magnetic moment of a lithographically defined micron-sized superconducting Nb ring, a key element for the previously proposed subpiconewton force standard. The magnetic moments due to individual magnetic fluxoids and a diamagnetic response were independently determined at T = 4.3 K, with a subfemtoampere-square-meter resolution. The results show good agreement with the theoretical estimation yielded by the Brandt and Clem model within the spring constant determination accuracy.

cond-mat.mes-hall↗

arXiv2010

Superconducting Qubits Coupled to Torsional Resonators

We propose a scheme of strong and tunable coupling between a superconducting phase qubit and nanomechanical torsional resonator. In our scheme the torsional resonator directly modulates the largest energy scale (the Josephson coupling energy) of the phase qubit, and the coupling strength is very large. We analyze the quantum correlation effects in the torsional resonator as a result of the strong coupling to the phase qubit.

cond-mat.mes-hall↗

arXiv2006

Quantum-based Mechanical Force Realization in Pico-Newton Range

We propose mechanical force realization based on flux quantization in the pico-Newton range. By controlling the number of flux quantum in a superconducting annulus, a force can be created as integer multiples of a constant step. For a 50 nm-thick Nb annulus with the inner and outer radii of 5 $μ$m and 10 $μ$m, respectively, and the field gradient of 10 T/m the force step is estimated to be 184 fN. The stability against thermal fluctuations is also addressed.

cond-mat.mes-hall↗

arXiv2001

Superconducting properties of well-shaped MgB2 single crystal

We report measurements of the transport and the magnetic properties of high-quality, sub-millimeter-sized MgB2 single crystals with clear hexagonal-plate shapes. The low-field magnetization and the magnetic hysteresis curves show the vortex pinning of these crystals to be very weak. The Debye temperature of $Θ_{D}\sim 1100$ K, obtained from the zero-field resistance curve, suggests that the normal-state transport properties are dominated by electron-phonon interactions. The resistivity ratio between 40 K and 300 K was about 5, and the upper critical field anisotropy ratio was 3 $\pm$ 0.2 at temperatures around 32 K.

cond-mat.supr-con↗

arXiv2001

Three-Dimensional Superconductivity in the Infinite-Layer Compound Sr_{0.9}La_{0.1}CuO_2 in Entire Region below $T_c$

The infinite-layer compound ACuO$_{2}$ (A $=$ alkaline-earth ions) is regarded as the most suitable material for exploring the fundamental nature of the CuO$_2$ plane because it does not contain a charge-reservoir block, such as a rock-salt or a fluorite like block. We report that superconductivity in the infinite-layer compound Sr$_{0.9}$La$_{0.1}$CuO$_2$ is of a three-dimensional nature, in contrast to the quasi two-dimensional superconducting behavior of all other cuprates. The key observation is that the $c$-axis coherence length is longer than the $c$-axis lattice constant even at zero temperature. This means that the superconducting order parameter of one CuO$_{2}$ plane overlaps with those of neighboring CuO$_{2}$ planes all the temperatures below the $T_c$. Among all cuprates, only the infinite-layer superconductor shows such a feature.

cond-mat.supr-con↗