arXiv subjects

Stanislau U. Piatrusha

Publications and source records attributed to Stanislau U. Piatrusha.

3 recordsLinked to original sources

arXiv2025

Wiedemann-Franz behavior at the Weyl points in compressively strained HgTe

Weyl semimetals, with their unique electronic band structure, have drawn significant interest for their potential to explore quantum anomalies in condensed matter systems. In this study, we investigate the large positive magneto-thermal conductance associated with the gravitational anomaly -- one of the predicted anomalies -- for a Weyl semimetal based on a compressively strained HgTe layer. We clearly identify the Weyl regime in our device and accurately extract the thermal conductance by performing thermometry measurements at liquid helium temperatures using fully electronic methods. We observe the anticipated increase in thermal conductance, and it perfectly matches the electrical conductance according to the Wiedemann-Franz law. This finding indicates that, despite the unique electronic spectrum of Weyl semimetals, the mechanism governing heat transport in this system is the same as that for electrical transport, with no additional violations of conservation laws.

cond-mat.mes-hall↗

arXiv2024

Phase-dependent supercurrent and microwave dissipation of HgTe quantum well Josephson junctions

We measured the microwave response of a HgTe quantum well Josephson junction embedded into an RF SQUID loop which is inductively coupled to a superconducting resonator. The side-contacted devices studied here operate in bulk transport mode, with a separation between the superconducting contacts smaller than both the estimated carrier mean free path and superconducting coherence length. We extract the current-phase relation and the phase-dependent microwave dissipation, that, at low temperature, primarily is related to photon-induced transitions between the Andreev bound states. We study the effects of gate voltage and temperature on our devices and compare the measurements with a tight-binding model based on the Bogoliubov-de Gennes equations. A combined analysis of both microwave admittance components allows us to confirm the presence of a small gap in the Andreev bound state spectrum at phase $π$, indicating high interface transparency, matching our observations in DC measurements of a similar device. Our work demonstrates the versatility of microwave measurements as a tool for Josephson junction characterization and highlights the importance of the interface properties for side-contacted Josephson devices.

cond-mat.supr-con↗

arXiv2024

Period-doubling in the phase dynamics of a shunted HgTe quantum well Josephson junction

The fractional AC Josephson effect is a discerning property of topological superconductivity in hybrid Josephson junctions. Recent experimental observations of missing odd Shapiro steps and half Josephson frequency emission in various materials have sparked significant debate regarding their potential origin in the effect. In this study, we present microwave emission measurements on a resistively shunted Josephson junction based on a HgTe quantum well. We demonstrate that, with significant spurious inductance in the shunt wiring, the experiment operates in a nonlinear dynamic regime characterized by period-doubling. This leads to additional microwave emission peaks at half of the Josephson frequency, $f_J/2$, which can mimic the $4π$-periodicity of topological Andreev states. The observed current-voltage characteristics and emission spectra are well-described by a simple RCLSJ model. Furthermore, we show that the nonlinear dynamics of the junction can be controlled using gate voltage, magnetic field, and temperature, with our model accurately reproducing these effects without incorporating any topological attributes. Our observations urge caution in interpreting emission at $f_J/2$ as evidence for gapless Andreev bound states in topological junctions and suggest the appropriate parameter range for future experiments.

cond-mat.mes-hall↗