arXiv subjects

X. Y. Tee

Publications and source records attributed to X. Y. Tee.

6 recordsLinked to original sources

arXiv2021

Skyrmion-(Anti)Vortex Coupling in a Chiral Magnet-Superconductor Heterostructure

We report experimental coupling of chiral magnetism and superconductivity in [IrFeCoPt]/Nb heterostructures. The stray field of skyrmions with radius ~50nm is sufficient to nucleate antivortices in a 25nm Nb film, with unique signatures in the magnetization, critical current and flux dynamics, corroborated via simulations. We also detect a thermally-tunable Rashba-Edelstein exchange coupling in the isolated skyrmion phase. This realization of a strongly interacting skyrmion-(anti)vortex system opens a path towards controllable topological hybrid materials, unattainable to date.

cond-mat.supr-con↗

arXiv2021

A perpendicular field electromagnet with a 250mm access bore

We present a laboratory electromagnet capable of generating magnetic fields up to $\pm$0.48T, specifically designed as a perpendicular flux source for thin film samples in an ambient environment. The magnet features a 250mm diameter clear access bore above the sample plane, thus offering compatibility with a wide variety of experimental apparatus. Despite its generous size, the magnet thermally dissipates less than 1kW at maximum field. A shaped ferromagnetic core is used to amplify and homogenize the field $\mathbf{B}$, leading to an estimated uniformity of $\pm$1.5mT ($\lesssim$0.3%) in $\left|\mathbf{B}\right|$ within a 28mm$^2$ zone at maximum field. The sample stage is thermally regulated and isolated from the magnet, enabling temperature control with $\pm$5mK precision even at elevated magnetic fields.

physics.ins-det↗

arXiv2020

An Ultra-High-Vacuum Rotating Sample Manipulator with Cryogenic Cooling

We report a homebuilt ultra-high-vacuum (UHV) rotating sample manipulator with cryogenic cooling. The sample holder is thermally anchored to a built-in cryogenic cold head through flexible copper beryllium strips, permitting continuous sample rotation. A similar contact mechanism is implemented for the electrical wiring to the sample holder for thermometry. The apparatus thus enables continuous sample rotation at regulated cryogenic temperatures in a UHV environment. We discuss the potential applications of this apparatus for cryogenic sputtering.

physics.ins-det↗

arXiv2016

Two Superconducting Transitions in Single Crystal La$_{2-x}$Ba$_x$CuO$_4$

We use spatially-resolved transport techniques to investigate the superconducting properties of single crystals La$_{2-x}$Ba$_x$CuO$_4$. We find a new superconducting transition temperature $T_{cs}$ associated with the ab-plane surface region which is considerably higher than the bulk $T_c$. The effect is pronounced in the region of charge carrier doping $x$ with strong spin-charge stripe correlations, reaching $T_{cs}=36$ K or 1.64$T_c$.

cond-mat.supr-con↗

arXiv2015

Multiple Broken Symmetries in Striped La$_{2-x}$Ba$_{x}$CuO$_{4}$ detected by the Field Symmetric Nernst Effect

We report on a thermoelectric investigation of the stripe and superconducting phases of the cuprate La$_{2-x}$Ba$_{x}$CuO$_{4}$ near the $x=1/8$ doping known to host stable stripes. We use the doping and magnetic field dependence of field-symmetric Nernst effect features to delineate the phenomenology of these phases. Our measurements are consistent with prior reports of time-reversal symmetry breaking signatures above the superconducting $T_{\rm c}$, and crucially detect a sharp, robust, field-invariant peak at the stripe charge order temperature, $T_{\rm {\scriptscriptstyle CO}}$. Our observations suggest the onset of a nontrivial charge ordered phase at $T_{\rm {\scriptscriptstyle CO}}$, and the subsequent presence of spontaneously generated vortices over a broad temperature range before the emergence of bulk superconductivity in LBCO.

cond-mat.supr-con↗

arXiv2012

Penetration depth study of LaOs$_4$Sb$_{12}$: Multiband s-wave superconductivity

We measured the magnetic penetration depth $λ(T)$ in single crystals of LaOs$_{4}$Sb$_{12}$ ($T_c$=0.74 K) down to 85 mK using a tunnel diode oscillator technique. The observed low-temperature exponential dependence indicates a s-wave gap. Fitting the low temperature data to BCS s-wave expression gives the zero temperature gap value $Δ(0)= (1.34 \pm 0.07) k_B T_c$ which is significantly smaller than the BCS value of 1.76$k_B T_c$. In addition, the normalized superfluid density $ρ(T)$ shows an unusually long suppression near $T_c$, and are best fit by a two-band s-wave model.

cond-mat.supr-con↗