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A. Ariando

Publications and source records attributed to A. Ariando.

At least 19 recordsLinked to original sources
arXiv2026

Ni-O hybridization-driven electronic reconstruction across the superconducting dome in an infinite-layer nickelate

Superconductivity in infinite-layer nickelates has drawn wide interest as a cuprate analogue, yet how the electronic structure evolves with hole doping remains unsettled. Here we map the doping- and temperature-dependent unoccupied states of the La-based infinite-layer nickelate La1-xCaxNiO2 using O K-edge and Ni L-edge x-ray absorption spectroscopy. Superconductivity occurs for 0.18<=x<=0.27. Near x~0.20-0.23, low-energy spectral weight redistributes: Ni3d-dominated states decrease while O2p-hybridized states increase, indicating an orbital-selective crossover in Ni-O covalency. This crossover coincides with a sign reversal of the Hall coefficient and precedes the reduction of the superconducting critical temperature at higher doping. By directly linking transport anomalies and the superconducting dome to a measurable Ni-O orbital reorganization, our results provide a key step toward a unified, orbital-resolved phase diagram for infinite-layer nickelates and a practical route to engineer superconductivity via hybridization control.

cond-mat.supr-con↗
arXiv2026

Hole-doped superconductivity above 100 K in infinite-layer cuprate thin films

Since the discovery of superconductivity in (La,Ba)2CuO2 (Ref.~\cite{bednorz1986possible}), a broad family of structurally distinct cuprate superconductors has been proposed or engineered to elucidate the physics of high-temperature superconductivity~\cite{chu2015hole,plakida2010high}. Among them, the infinite-layer cuprate has the simplest structure, consisting only of the essential ingredients for superconductivity: CuO$_2$ square planes separated by spacer ions~\cite{siegrist1988parent}. Despite being proposed nearly 40 years ago, the hole-doped superconductivity via chemical substitution in this compound has not yet been achieved, a fundamental open question in the field. Here, we report the observation of superconductivity in the hole-doped infinite-layer cuprate thin film. Measurements of resistivity and magnetic-field response in Sr1-xRbxCuO2 single-crystal thin films show superconducting transitions with a high onset temperature of 100 K. Hole doping is achieved via the synergistic effect of rubidium substitution and apical oxygen incorporation, as evidenced by structural analysis and transport measurements. As the parent structure of the cuprate family~\cite{chu2015hole}, hole-doped infinite-layer cuprate provides a unique platform for revisiting key puzzles in cuprate superconductors~\cite{keimer2015quantum,tsuei2000pairing,armitage2010progress,dagotto1994correlated}, including strange metal~\cite{proust2019remarkable,taillefer2010scattering} and electron-hole symmetry~\cite{tohyama2004asymmetry,segawa2010zero,lee2014asymmetry}, while bridging to cuprate-nickelate symmetry~\cite{li2019superconductivity,zeng2022superconductivity,chow2025bulk,lechermann2020late}.

cond-mat.supr-con↗
arXiv2026

Thickness-driven crossover from conventional to chiral nonreciprocal superconductivity in kagome metal CsV3Sb5

Superconductivity and its potential applications are governed by the symmetry of the superconducting order parameter. In the kagome metal CsV3Sb5, most bulk studies indicate conventional s-wave pairing. However, ultrathin flakes exhibit nonreciprocal transport, in particular a zero-field superconducting diode effect, which requires broken inversion and time-reversal symmetries. Here, using thickness dependent transport measurements, we observe the emergence of non-reciprocal second-harmonic magnetotransport signals and a zero-field superconducting diode effect, accompanied by a pronounced reduction of the out-of-plane coherence length with decreasing thickness. Upper critical field measurements further reveal a dimensional crossover from three-dimensional superconductivity in bulk to two-dimensional superconductivity in thin flakes. These findings indicate a thickness-induced chiral superconducting phase that breaks both inversion and time-reversal symmetries in the two-dimensional limit. Our work not only clarifies long-standing controversies regarding the pairing symmetry in CsV3Sb5, but also establishes thin-flake kagome superconductors as a versatile platform for engineering nonreciprocal quantum devices and exploring emergent topological phases.

cond-mat.supr-con↗
arXiv2025

Modulation of Quantum Transport in Complex Oxide Heterostructures with Proton Implantation

The interfacial electronic properties of complex oxides are governed by a delicate balance between charge transfer, lattice distortions, and electronic correlations, posing a key challenge for controlled tunability in materials research. Here, we demonstrate that proton implantation serves as a precise tool for modulating interfacial transport in SrTiO3-based heterostructures. By introducing protons into the SrTiO3 substrate beneath an amorphous (La,Sr)(Al,Ta)O3 capping layer, we uncover a competition between disorder and charge doping induced by implantation. At low implantation fluences below 1x1015 protons/cm2 (1E15), charge doping dominates, leading to an increase in carrier density and mobility, analogous to electrostatic gating effect. This enables the emergence of quantum transport oscillations at low temperature. Conversely, at higher fluences (above 1E15), disorder scattering prevails, suppressing carrier mobility and inducing an insulating state. The nonmonotonic evolution of transport with implantation fluence underscores the critical interplay between electronic correlations and disorder, offering a new paradigm for the controlled engineering of interfacial quantum states in SrTiO3-based oxide heterostructures.

cond-mat.mtrl-sci↗
arXiv2025

High-field-stabilized reentrant superconductivity in infinite-layer nickelate thin films

Magnetic fields typically suppress superconductivity through Pauli and orbital limiting effects. However, there are rare instances of magnetic-field-induced superconductivity, as seen in Chevrel phase compounds [1], organic conductors [2], uranium-based heavy-fermion systems [3, 4], and moire graphene [5], though these materials possess inherently low superconducting transition temperatures (Tc). Here, we demonstrate high field-stabilized superconductivity in a class of materials with a significantly higher Tc (up to 40 K): the infinite-layer nickelates [6]. Both low-field and high-field superconducting states can be plausibly explained by a compensation mechanism akin to the Jaccarino-Peter effect. These findings demonstrate the possibility of achieving substantially enhanced upper critical fields in high-temperature superconductors.

cond-mat.supr-con↗
arXiv2025

Electrostatic gate-controlled quantum interference in a high-mobility two-dimensional electron gas at the (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)O$_3$/SrTiO$_3$ interface

We report quantum oscillations in magnetoresistance that are periodic in magnetic field ($B$), observed at the interface between (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)O$_3$ and SrTiO$_3$. Unlike Shubnikov-de Haas oscillations, which appear at magnetic fields $ > 7$ T and diminish quickly as the temperature rises, these $B$-periodic oscillations emerge at low fields and persist up to 10 K. Their amplitude decays exponentially with both temperature and field, specifying dephasing of quantum interference. Increasing the carrier density through electrostatic gating results in a systematic reduction in both the amplitude and frequency of the oscillations, with complete suppression beyond a certain gate voltage. We attribute these oscillations to the Altshuler-Aronov-Spivak effect, likely arising from naturally formed closed-loop paths due to the interconnected quasi-one-dimensional conduction channels along SrTiO$_3$ domain walls. The relatively long phase coherence length ($\sim$ 1.8 $\mu$m at 0.1 K), estimated from the oscillation amplitude, highlights the potential of complex oxide interfaces as a promising platform for exploring quantum interference effects and advancing device concepts in quantum technologies, such as mesoscopic interferometers and quantum sensors.

cond-mat.mes-hall↗
arXiv2025

Persistent paramagnons in high-temperature infinite-layer nickelate superconductors

The recent discovery of high-temperature superconductivity in hole-doped SmNiO$_2$, exhibiting the record-high transition temperature $T_c$ among infinite-layer (IL) nickelates, has opened a new avenue for exploring design principles of superconductivity. Experimentally determining the electronic structure and magnetic interactions in this new system is crucial to elucidating the mechanism behind the enhanced superconductivity. Here, we report a Ni $L$-edge resonant inelastic x-ray scattering (RIXS) study of superconducting Sm-based IL nickelate thin films Sm$_{1-x-y-z}$Eu$_x$Ca$_y$Sr$_z$NiO$_2$ (SECS). Dispersive paramagnonic excitations are observed in both optimally and overdoped SECS samples, supporting a spin-fluctuation-mediated pairing scenario. However, despite the two-fold enhancement of $T_c$ in the Sm-based nickelates compared to their Pr-based counterparts, the effective exchange coupling strength is reduced by approximately $20\%$. This behavior contrasts with hole-doped cuprates, where magnetic interactions correlate positively with $T_c$, highlighting essential differences in their superconducting mechanisms.

cond-mat.supr-con↗
arXiv2024

High-temperature Superconducting Oxide without Copper at Ambient Pressure

The discovery of superconductivity in the Ba-La-Cu-O system (the cuprate) at the 30 K range in 1986 marked a significant breakthrough, as it far exceeded the highest known critical temperature ($T_c$) at the time and surpassed the predicted 30 K limit, which was thought to be the maximum before phonon-mediated electron pairing would break down due to thermal excitation. Despite recent successful observations of superconductivity in nickel-oxide-based compounds (the nickelate), superconductivity above 30 K at ambient pressure in a system that is isostructural and isoelectronic to the cuprate but without copper has remained elusive. Here, we report a superconducting $T_c$ above 35 K under ambient pressure in hole-doped, late rare-earth infinite-layer nickel oxide (Sm-Eu-Ca-Sr)NiO$_2$ thin films. Electron microscopy reveals a small thickness of ~2 nm of infinite-layer phase stabilised at present, which indicates a higher temperature superconductivity should be observable in clean bulk crystals.

cond-mat.supr-con↗
arXiv2024

Hydrogen is not necessary for superconductivity in topotactically reduced nickelates

A key open question in the study of layered superconducting nickelate films is the role that hydrogen incorporation into the lattice plays in the appearance of the superconducting state. Due to the challenges of stabilizing highly crystalline square planar nickelate films, films are prepared by the deposition of a more stable parent compound which is then transformed into the target phase via a topotactic reaction with a strongly reducing agent such as CaH$_2$. Recent studies, both experimental and theoretical, have introduced the possibility that the incorporation of hydrogen from the reducing agent into the nickelate lattice may be critical for the superconductivity. In this work, we use secondary ion mass spectrometry to examine superconducting La$_{1-x}$X$_x$NiO$_2$ / SrTiO$_3$ (X = Ca and Sr) and Nd$_6$Ni$_5$O$_{12}$ / NdGaO$_3$ films, along with non-superconducting NdNiO$_2$ / SrTiO$_3$ and (Nd,Sr)NiO$_2$ / SrTiO$_3$. We find no evidence for extensive hydrogen incorporation across a broad range of samples, including both superconducting and non-superconducting films. Theoretical calculations indicate that hydrogen incorporation is broadly energetically unfavorable in these systems, supporting our conclusion that hydrogen incorporation is not generally required to achieve a superconducting state in layered square-planar nickelates.

cond-mat.supr-con↗
arXiv2024

On the origin of topotactic reduction effect for superconductivity in infinite-layer nickelates

Topotactic reduction utilizing metal hydrides as reagents emerges as an effective approach to achieve exceptionally low oxidization states of metal ions and unconventional coordination networks. This method opens avenues to the development of entirely new functional materials, with one notable example being the infinite-layer nickelate superconductors. However, the reduction effect on the atomic reconstruction and electronic structures -- crucial for superconductivity -- remains largely unresolved. We design two sets of control Nd$_{0.8}$Sr$_{0.2}$NiO$_2$ thin films and implement secondary ion mass spectroscopy to highlight the absence of reduction-induced hydrogen intercalation. X-ray absorption spectroscopy shows a significant linear dichroism with dominant Ni 3d$_{x2{-}y2}$ orbitals on superconducting samples, indicating a Ni single-band nature of infinite-layer nickelates. Consistent with the superconducting $T_c$, the Ni 3d orbitals asymmetry manifests a dome-like reduction duration dependence. Our results unveil the critical role of reduction in modulating the Ni-3d orbital polarization and its impact on the superconducting properties.

cond-mat.supr-con↗
arXiv2023

Holographic imaging of antiferromagnetic domains with in-situ magnetic field

Lensless coherent x-ray imaging techniques have great potential for high-resolution imaging of magnetic systems with a variety of in-situ perturbations. Despite many investigations of ferromagnets, extending these techniques to the study of other magnetic materials, primarily antiferromagnets, is lacking. Here, we demonstrate the first (to our knowledge) study of an antiferromagnet using holographic imaging through the "holography with extended reference by autocorrelation linear differential operation" technique. Energy-dependent contrast with both linearly and circularly polarised x-rays are demonstrated. Antiferromagnetic domains and topological textures are studied in the presence of applied magnetic fields, demonstrating quasi-cyclic domain reconfiguration up to 500 mT.

cond-mat.mes-hall↗
arXiv2023

Tunable Magnetic Properties in Sr$_2$FeReO$_6$ Double-Perovskite

Double-perovskite oxides have attracted recent attention due to their attractive functionalities and application potential. In this paper, we demonstrate the effect of dual controls, i.e., the deposition pressure of oxygen (P$_O2$) and lattice mismatch ($\epsilon$), on tuning magnetic properties in epitaxial double-perovskite Sr$_2$FeReO$_6$ films. In a nearly-lattice-matched Sr$_2$FeReO$_6$/SrTiO$_3$ film, the ferrimagnetic-to-paramagnetic phase transition occurs when P$_O2$ is reduced to 30 mTorr, probably due to the formation of Re$^{4+}$ ions that replace the stoichiometric Re$^{5+}$ to cause disorders of $B$-site ions. On the other hand, a large compressive strain or tensile strain shifts this critical P$_O2$ to below 1 mTorr or above 40 mTorr, respectively. The observations could be attributed to the modulation of $B$-site ordering by epitaxial strain through affecting elemental valence. Our results provide a feasible way to expand the functional tunability of magnetic double-perovskite oxides that hold great promise for spintronic devices.

cond-mat.str-el↗
arXiv2023

Scanning SQUID-on-tip microscope in a top-loading cryogen-free dilution refrigerator

The scanning superconducting quantum interference device (SQUID) fabricated on the tip of a sharp quartz pipette (SQUID-on-tip) has emerged as a versatile tool for nanoscale imaging of magnetic, thermal, and transport properties of microscopic devices of quantum materials. We present the design and performance of a scanning SQUID-on-tip microscope in a top-loading probe of a cryogen-free dilution refrigerator. The microscope is enclosed in a custom-made vacuum-tight cell mounted at the bottom of the probe and is suspended by springs to suppress vibrations caused by the pulse tube cryocooler. Two capillaries allow in-situ control of helium exchange gas pressure in the cell that is required for thermal imaging. A nanoscale heater is used to create local temperature gradients in the sample, which enables quantitative characterization of the relative vibrations between the tip and the sample. The spectrum of the vibrations shows distinct resonant peaks with maximal power density of about 27 nm/Hz$^{1/2}$ in the in-plane direction. The performance of the SQUID-on-tip microscope is demonstrated by magnetic imaging of the MnBi$_2$Te$_4$ magnetic topological insulator, magnetization and current distribution imaging in a SrRuO$_3$ ferromagnetic oxide thin film, and by thermal imaging of dissipation in graphene.

cond-mat.mes-hall↗
arXiv2023

High-quality NiFe thin films on oxide/non-oxide platforms via pulsed laser deposition at room temperature

Soft ferromagnetic NiFe thin films are promising for applications in spintronic devices because of their constituent electrical and magnetic properties. Electron beam evaporation and sputtering techniques have been used to deposit NiFe thin films. For in-situ stacking of NiFe with functional complex oxides, the pulsed laser deposition (PLD) method is highly desirable. However, the growth of high-quality NiFe (and non-oxide thin films in general) by PLD remains a formidable task. Here, we report high-quality NiFe thin films of various thicknesses on oxide/non-oxide substrates with desirable magnetic properties by PLD at room temperature. The magnetic properties are found to be strongly dependent on the laser fluence of the deposition process. The laser fluence of 4 Joule/cm$^2$ produces the highest magnetization of ~547 emu/cc. The small coercivity (few Oersted) and sharp ferromagnetic switching behaviour indicate uniaxial anisotropy with an easy axis along the in-plane direction. In addition, thickness-dependent magnetodynamics characterizations are studied via ferromagnetic resonance. Our findings indicate the ferromagnetic characteristics are sensitive to the quality of the oxide/non-oxide substrate surface. These results offer significant insight into the PLD-based development of thin metal magnetic films.

cond-mat.mtrl-sci↗
arXiv2023

Magnetic proximity effect at the interface of two-dimensional materials and magnetic oxide insulators

Two-dimensional (2D) materials provide a platform for developing novel spintronic devices and circuits for low-power electronics. In particular, inducing magnetism and injecting spins in graphene have promised the emerging field of graphene spintronics. This review focuses on the magnetic proximity effect at the interface of 2D materials and magnetic oxide insulators. We highlight the unique spin-related phenomena arising from magnetic exchange interaction and spin-orbital coupling in 2D materials coupled with magnetic oxides. We also describe the fabrication of multifunctional hybrid devices based on spin transport. We conclude with a perspective of the field and highlight challenges for the design and fabrication of 2D spintronic devices and their potential applications in information storage and logic devices.

cond-mat.mtrl-sci↗
arXiv2023

A Robust High-temperature Multiferroic Device with Tunable Topological Hall Effect

We fabricated Pt/La0.5Ba0.5MnO3 ultrathin films with integration to the PbZr0.2Ti0.8O3 ferroelectric. Strong Topological Hall Effect can be measured across a wide temperature range, which can be turned on and off corresponding to the ferroelectric polarization switching driven by short voltage pulses, indicating creation and annihilation of magnetic Skyrmions. However, its magnetoelectric coupling polarity was found to be opposite to the earlier consensus, which involves a phase transition between ferromagnetic and A-type antiferromagnetic in manganites due to electrostatic doping into the eg-orbitals by the ferroelectric bound charges. In our case, we propose a novel yet complementary picture where the transition occurs between C-type antiferromagnetic and ferromagnetic. The distinction between the earlier consensus and our picture lies at the tetragonal distortion of the manganite unit cell, resulting in an opposite magnetoelectric coupling polarity. We support the perceived relationship between the phase transition and tuning of Topological Hall Effect by micromagnetic simulations.

cond-mat.mtrl-sci↗
arXiv2023

Dimensionality control and rotational symmetry breaking superconductivity in square-planar layered nickelates

The interplay between dimensionality and various phases of matter is a central inquiry in condensed matter physics. New phases are often discovered through spontaneously broken symmetry. Understanding the dimensionality of superconductivity in the high-temperature cuprate analogue $-$ layered nickelates and revealing a new symmetry-breaking state are the keys to deciphering the underlying pairing mechanism. Here, we demonstrate the highly-tunable dimensionality and a broken rotational symmetry state in the superconductivity of square-planar layered nickelates. The superconducting state, probed by superconducting critical current and magnetoresistance within superconducting transition under direction-dependent in-plane magnetic fields, exhibits a $C_2$ rotational symmetry which breaks the $C_4$ rotational symmetry of the square-planar lattice. Furthermore, by performing detailed examination of the angular dependent upper critical fields at temperatures down to 0.5 K with high-magnetic pulsed-fields, we observe a crossover from two-dimensional to three-dimensional superconducting states which can be manipulated by the ionic size fluctuations in the rare-earth spacer layer. Such a large degree of controllability is desired for tailoring strongly two/three-dimensional superconductors and navigating various pairing landscapes for a better understanding of the correlation between reduced dimensionality and unconventional pairing. These results illuminate new directions to unravel the high-temperature superconducting pairing mechanism.

cond-mat.supr-con↗
arXiv2022

Ionic modulation at the LaAlO$_3$/KTaO$_3$ interface for extreme high-mobility two-dimensional electron gas

Due to the coexistence of many emergent phenomena, including 2D superconductivity and a large Rashba spin-orbit coupling, 5d transition metal oxides based two-dimensional electron systems (2DESs) have been prospected as one of the potential intrants for modern electronics. However, despite the lighter electron mass, the mobility of carriers, a key requisite for high-performance devices, in 5d-oxides devices remains far behind their 3d-oxides analogs. The carriers mobility in these oxides is significantly hampered by the inevitable presence of defects generated during the growth process. Here, we report very high mobility ($\sim$ 22650 cm$^2$V$^{-1}$s$^{-1}$) of 5d-2DES confined at the LaAlO$_3$/KTaO$_3$ interface. The high mobility, which is beyond the values observed in LaAlO$_3$/SrTiO$_3$ and $\gamma$-Al$_2$O$_3$/SrTiO$_3$ systems in the same carrier-density range, is achieved using the ionic-liquid gating at room temperature. We postulate that the ionic-liquid gating affects the oxygen vacancies and efficiently reduces any disorder at the interface. Investigating density and mobility in a broad range of back-gate voltage, we reveal that the mobility follows the power-law $\mu \propto n^{1.2}$, indicating the very high quality of ionic-liquid-gated LaAlO$_3$/KTaO$_3$ devices, consistent with our postulate. Further, the analysis of the quantum oscillations measured in high magnetic fields confirms that the high-mobility electrons occupy the electronic sub-bands emerging from the Ta:5d orbitals of KTaO$_3$.

cond-mat.mtrl-sci↗