arXiv subjects

Aeron McConnell

Publications and source records attributed to Aeron McConnell.

7 recordsLinked to original sources

arXiv2026

Persistent Interfacial Topological Hall Effect Demonstrating Electrical Readout of Topological Spin Structures in Insulators

Conventional topological Hall effects (THE) require conducting magnets, leaving insulating systems largely inaccessible. Here we introduce the interfacial topological Hall effect (ITHE), where the noncoplanar spin textures of insulating magnets are imprinted onto an adjacent heavy metal via the magnetic proximity effect (MPE) and detected electrically. In Pt/h-LuFeO3 bilayers, h-LuFeO3 hosts a topological spin structure robust against high magnetic fields, arising from a 120° triangular spin lattice with small spin canting that yields nontrivial topology but minimal magnetization. This generates a giant Hall response in Pt up to 0.5% of the longitudinal resistivity and a Hall-conductivity/magnetization ratio above 2 V^{-1}, clearly distinguishable from the spin Hall Hanle effect background. Field- and temperature-dependent analysis further reveals that Pt nanoclusters inherit topological textures from h-LuFeO3 via MPE. Unlike the conventional THE narrow peak-and-dip features, ITHE in Pt/h-LuFeO3 persists across a broad magnetic field range up to 14 T, demonstrating the exceptional stability of the underlying topological spin structure. This establishes ITHE as a powerful and sensitive probe for topological magnetism in ultrathin insulating films and paves the way for new spintronic applications.

cond-mat.mtrl-sci↗

arXiv2025

Chirality-induced magnetoresistance in hybrid organic-inorganic perovskite semiconductors

The combination of semiconducting properties and synthetically tunable chirality in chiral metal halide semiconductors (CMHS) offer a compelling platform for room temperature control over electronic spin properties, leveraging effects such as chirality-induced spin selectivity (CISS) for the development of new opto-spintronic functionalities. We report room-temperature CISS-induced magnetoresistance (CISS-MR) exceeding 100% for spin valves in a configuration consisting of a ferromagnet (FM), tunneling barrier, and CMHS. The high CISS-MR is attributed to interfacial spin-selective tunneling barrier induced by the chirality, which can produce current dissymmetry factors that surpass the limit imposed by the Jullière model governed by the intrinsic spin polarization of the adjacent FM contact. The CISS-MR exhibits a strong dependence on the CMHS composition, revealing a structure-property relationship between CISS and structural chirality. The observed exceptionally large tunneling MR response differentiates from a subtle anisotropic MR arising from the proximity effect at the FM/CMHS interface in the absence of a tunneling barrier. Our study provides insights into charge-to-spin interconversion in chiral semiconductors, offering materials design principles to control and enhance CISS response and utilize it in functional platforms.

cond-mat.mtrl-sci↗

arXiv2023

Giant interfacial spin-Hall angle from Rashba-Edelstein effect revealed by the spin-Hall Hanle processes

The Rashba-Edelstein effect (REE), which generates interfacial spin polarization and subsequent spin current, is a compelling spin-charge conversion mechanism for spintronics applications, since it is not limited by the elemental spin-orbit coupling. In this work, we demonstrate REE at Pt/ferroelectric interfaces using the recently elucidated spin-Hall Hanle effects (SHHE), in which a Larmor precession of spin polarization in a diffusion process from the interface manifest as magnetoresistance and Hall effect. We show that REE leads to a three-fold enhancement of the effective spin Hall angle in ferroelectric interface Pt/h-LuFeO3 compared to that of Pt /Al2O3, although the difference in the spin relaxation time is negligible. Modeling using SHHEs involving REE as an additional source of interfacial polarization suggests that REE can lead to an interfacial spin Hall angle (~0.3) that is one order of magnitude larger than the bulk value of Pt. Our results demonstrate that a ferroelectric interface can produce large spin-charge conversion and that SHHEs are a sensitive tool for characterizing interfacial spin transport properties.

cond-mat.mes-hall↗

arXiv2022

Phase dynamics in an AC driven multiterminal Josephson junction analogue

In the presence of an AC drive, multiterminal Josephson junctions exhibit the inverse AC Josephson effect, where the oscillations of the superconducting phase of each junction can lock onto one another or onto the external drive. The competition between these different phase locked states results in a complex array of quantized voltage plateaus whose stability strongly depend on the circuit parameters of the shunted junctions. This phase diagram cannot be explored with low temperature transport experiments alone, given the breadth of the parameter space, so we present an easily tunable analog circuit whose dynamical properties emulate those of a three terminal junction. We focus on the observation of the multiterminal inverse AC Josephson effect, and we discuss how to identify Shapiro steps associated with each of the three junctions as well as their quartet states. We only observe integer phase locked states in strongly overdamped networks, but fractional Shapiro steps appear as well when the quality factor of the junctions increases. Finally, we discuss the role of transverse coupling in the synchronization of the junctions.

cond-mat.supr-con↗

arXiv2022

Dynamical Stabilization of Multiplet Supercurrents in Multi-terminal Josephson Junctions

The dynamical properties of multi-terminal Josephson junctions have recently attracted interest, driven by the promise of new insights into synthetic topological phases of matter and Floquet states. This effort has culminated in the discovery of Cooper multiplets, in which the splitting of a Cooper pair is enabled via a series of Andreev reflections that entangle four (or more) electrons. In this text, we show conclusively that multiplet resonances can also emerge as a consequence of the three terminal circuit model. The supercurrent appears due to the correlated phase dynamics at values that correspond to the multiplet condition $nV_1 = -mV_2$ of applied bias. The emergence of multiplet resonances is seen in i) a nanofabricated three-terminal graphene Josephson junction, ii) an analog three terminal Josephson junction circuit, and iii) a circuit simulation. The mechanism which stabilizes the state of the system under those conditions is purely dynamical, and a close analog to Kapitza's inverted pendulum problem. We describe parameter considerations that best optimize the detection of the multiplet lines both for design of future devices. Further, these supercurrents have a classically robust $\cos2ϕ$ energy contribution, which can be used to engineer qubits based on higher harmonics.

cond-mat.mes-hall↗

arXiv2021

Phase locking and noise driven dynamics in a Josephson junction electronic analog

We present an electronic circuit whose dynamical properties emulate those of a resistively and capacitively shunted Josephson junction (RCSJ). We show how it reproduces the switching properties of a shunted junction and its dependence on the quality factor. A thermal noise source is then used to characterize the temperature dependence of the phase dynamics. In the presence of an AC drive, phase locking is observed at integer and rational multiples of the drive frequency, and it competes with chaotic behavior when the quality factor of the junction exceeds unity. We characterize the stability of phase-locked and chaotic states in the presence of thermal noise.

cond-mat.supr-con↗

arXiv2021

The Multi-terminal Inverse AC Josephson Effect

When a Josephson junction is exposed to microwave radiation, it undergoes the inverse AC Josephson effect - the phase of the junction locks to the drive frequency. As a result, the I-V curves of the junction acquire "Shapiro steps" of quantized voltage. If the junction has three or more superconducting contacts, coupling between different pairs of terminals must be taken into account and the state of the junction evolves in a phase space of higher dimensionality. Here, we study the multi-terminal inverse AC Josephson effect in a graphene sample with three superconducting terminals. We observe robust fractional Shapiro steps and correlated switching events, which can only be explained by considering the device as a completely connected Josephson network. We successfully simulate the observed behaviors using a modified two-dimensional RCSJ model. Our results suggest multi-terminal Josephson junctions are a playground to study highly-connected nonlinear networks with novel topologies.

cond-mat.mes-hall↗