arXiv subjects

Angela Moskal

Publications and source records attributed to Angela Moskal.

2 recordsLinked to original sources

arXiv2026

Energy-Resolved Cross-Correlation of THz Field Emission of Electrons from a Metal Nanotip

Intense THz pulses, combined with the lightning-rod field enhancement at metal nanotips, can drive field emission of keV-energy, femtosecond-duration electron bunches, yet the dynamics governing this emission remain largely unexplored. Here we probe these dynamics by cross-correlating the energy-resolved emission driven by two independently generated single-cycle THz pulses focused onto a tungsten nanotip, scanning their relative delay over 160 ps. At total bunch charges approaching $10^6$ e$^-$, the delay-energy emission map near zero delay reveals electrons accelerated up to 2.1 keV, with a cross-correlation width of ~210 fs full width at half maximum at the highest energies. Apart from replicas caused by optical reflections in the setup, no emission echoes are observed over the full delay range, ruling out long-lived antenna resonances such as Sommerfeld-wave reflections along the tip shaft. A 1D Fowler-Nordheim model incorporating a low-$Q$, sub-picosecond antenna response for the local field enhancement reproduces the peak electron energies and the asymmetry of the delay-energy map. Our results indicate that each THz pulse produces a single, isolated electron burst, and that energy filtering can select its shortest, highest-energy component.

cond-mat.mes-hall↗

arXiv2025

Competing Pair Density Wave and Uniform $d$-wave Superconductivity in Phase Separated 214 Cuprates at the 1/8 Anomaly

Compelling evidence exists for electronic phase separation in cuprate high-$T_c$ superconductors, emerging near 1/8 hole doping. At these dopings and low temperatures, intertwined charge and spin stripes coexist with more uniformly doped regions in the two-dimensional (2$D$) copper-oxide planes. Each region is capable of developing superconducting pairing, either as a pair density wave (PDW) within the stripes or as a uniform $d$-wave condensate ($d$-SC) in the more homogeneous regions. Using neutron scattering on single crystals of La$_{1.875-y}$Nd$_{y}$Sr$_{0.125}$CuO$_4$, we demonstrate that the onset temperatures for spin stripe order ($T_N$) and superconductivity ($T_c$) merge as the average ordered moment vanishes in LSCO ($y = 0$), whereas Nd doping stabilizes static stripe order and suppresses $T_c$. Because the spin stripes possess the same in-plane periodicity (8$a$) as the PDW and establish the framework in which the PDW resides, the stabilization of spin stripe order enhances PDW correlations. Thus, the competition between $d$-wave pairing in the uniform regions and PDW pairing in the stripe-ordered regions can be controlled by the Nd concentration in La$_{1.875-y}$Nd$_{y}$Sr$_{0.125}$CuO$_4$, allowing the superconducting $T_c$ to vary by nearly an order of magnitude at a fixed 1/8 hole doping.

cond-mat.str-el↗