A5061776650- Physics of Superconductivity and Magnetism
- Topological Materials and Phenomena
- Quantum and electron transport phenomena
- Semiconductor Quantum Structures and Devices
- Surface and Thin Film Phenomena
- 2D Materials and Applications
- Graphene research and applications
- Electronic and Structural Properties of Oxides
- Advanced Electrical Measurement Techniques
- Nanowire Synthesis and Applications
- Advancements in Semiconductor Devices and Circuit Design
- Semiconductor materials and devices
- Magnetic properties of thin films
- Advanced Semiconductor Detectors and Materials
- Iron-based superconductors research
- Genetic diversity and population structure
- Turtle Biology and Conservation
- Superconductivity in MgB2 and Alloys
- Wildlife Ecology and Conservation
- Heusler alloys: electronic and magnetic properties
- Quantum Information and Cryptography
- Advanced Condensed Matter Physics
- Advanced Memory and Neural Computing
- Solar and Space Plasma Dynamics
- Microwave Engineering and Waveguides
University of California, Santa Barbara
2020-2025
Indiana University – Purdue University Fort Wayne
2023
University of Southern California
2021
The phenomenon of non-reciprocal critical current in a Josephson device, termed the diode effect, has garnered much recent interest. Realization effect requires inversion symmetry breaking, typically obtained by spin-orbit interactions. Here we report observation three-terminal device based upon an InAs quantum well two-dimensional electron gas proximitized epitaxial aluminum superconducting layer. We demonstrate that efficiency our devices can be tuned small out-of-plane magnetic field or...
Move aside, aluminum Some of the most promising schemes for quantum information processing involve superconductors. In addition to established superconducting qubits, topological qubits may one day be realized in semiconductor-superconductor heterostructures. The superconductor widely used this context is aluminum, which processes that cause decoherence are suppressed. Pendharkar et al. go beyond paradigm show tin can place (see Perspective by Fatemi and Devoret). authors grew nanowires...
We study Josephson junctions based on InSb nanowires with Sn shells. observe skewed critical current diffraction patterns: the maxima in forward and reverse bias are at different magnetic flux, a displacement of 20-40 mT. The skew is greatest when external field nearly perpendicular to nanowire, substrate plane. This orientation suggests that spin-orbit interaction plays role. develop phenomenological model perform tight-binding calculations, both methods reproducing essential features...
The Andreev bound state spectra of multi-terminal Josephson junctions form an artificial band structure, which is predicted to host tunable topological phases under certain conditions. However, the number conductance modes between terminals junction must be few in order for this spectrum experimentally accessible. In work we employ a quantum point contact geometry three-terminal devices. We demonstrate independent control each pair and access single-mode regime coexistent with presence...
We investigate the current-phase relations of Al/InAs-quantum well planar Josephson junctions fabricated using nanowire shadowing technique. Based on several experiments, we conclude that exhibit an unusually large second-order harmonic, $\sin(2\varphi)$ term. First, superconducting quantum interference devices (dc-SQUIDs) show half-periodic oscillations, tunable by gate voltages as magnetic flux. Second, junction kinks near half-flux in supercurrent diffraction patterns. Third, half-integer...
Rare-earth monopnictide (RE-V) semimetal crystals subjected to hydrostatic pressure have shown interesting trends in magnetoresistance, magnetic ordering, and superconductivity, with theory predicting pressure-induced band inversion. Yet, thus far, there been no direct experimental reports of interchanged order RE-Vs due strain. This work studies the evolution topology biaxially strained GdSb(001) epitaxial films using angle-resolved photoemission spectroscopy (ARPES) density functional...
\ensuremath{\alpha}-Sn, the inversion symmetric analogue of HgTe, can be tuned through various topologically non-trivial phases by a combination strain and/or confinement effects. In addition, thin films \ensuremath{\alpha}-Sn have demonstrated very efficient spin-charge conversion. However, grown on InSb been plagued heavy incorporation p-type dopant indium. To better study and make use topological in this indium doping must minimized. The authors realize reduction tuning surface...
The electronic structure of various (001), (110), and (111)B surfaces n-type InSb were studied with scanning tunneling microscopy spectroscopy. InSb(111)B (3x1) surface reconstruction is determined to be a disordered (3x3) reconstruction. Fermi-level the In rich equal In:Sb reconstructions was observed pinned near valence band edge. This pinning consistent charge neutrality level lying maximum. Sb termination shift position by up $254 \pm 35$ meV towards conduction on (001) $60 surface. can...
Superconductor-semiconductor nanowire hybrid structures are useful in fabricating devices for quantum information processing. While selective area growth (SAG) offers the flexibility to grow semiconductor nanowires arbitrary geometries, situ evaporation of superconductors ensures pristine superconductor-semiconductor interfaces, resulting strong induced superconductivity semiconducting nanowire. In this work, we used high-aspect-ratio SiOx dielectric walls evaporate islands superconductor...
We study a Cooper pair transistor realized by two Josephson weak links that enclose superconducting island in an InSb-Al hybrid nanowire. When the nanowire is subject to magnetic field, isolated subgap levels arise and, because of Coulomb blockade, mediate supercurrent coherent cotunneling pairs. show resulting from such events exhibits, for low moderate fields, phase offset discriminates even and odd charge ground states on island. Notably, this persists when state approaches zero energy...
Strain solitons are quasi-dislocations that form in van der Waals materials to relieve the energy associated with lattice or rotational mismatch. Novel electronic properties of strain were predicted and observed. To date, have been observed only exfoliated crystals mechanically strained crystals. The lack a scalable approach toward generation poses significant challenge study use their properties. Here, we report formation epitaxial growth bismuth on InSb(111)B by molecular beam epitaxy....
High In content InGaAs quantum wells (In $\ensuremath{\ge}$ 75%) are potentially useful for topological computing and spintronics applications. high-mobility wells, alloy disorder scattering is a limiting factor. this paper, we demonstrate that by growing the as digital alloy, or short period superlattice, can reduce within well increase peak 2 K electron mobility to $545\phantom{\rule{0.16em}{0ex}}000 {\mathrm{cm}}^{2}$/Vs, which highest reported high-In best of authors' knowledge. Our...
Hybrid superconductor-semiconductor materials are fueling research in mesoscopic physics and quantum technology. Recently demonstrated smooth $\beta$-Sn superconductor shells, due to the increased induced gap, expanding available parameter space new regimes. Fabricated on quasiballistic InSb nanowires, with careful control over hybrid interface, Sn shells yield critical current-normal resistance products exceeding temperature by at least an order of magnitude even when nanowire is...
The Blanding’s Turtle (Emydoidea blandingii) is a species in need of conservation across much its geographic range. A key aspect to conserving understanding the genetic diversity and population structure landscape. Several researchers have focused on E. blandingii northeastern United States, Canada, parts Midwestern States; however, little investigation has been carried out localities within Great Lakes region Indiana, Michigan, Ohio. Understanding trends this will assist with planning by...
We study a Cooper-pair transistor realized by two Josephson weak links that enclose superconducting island in an InSb-Al hybrid nanowire. When the nanowire is subject to magnetic field, isolated subgap levels arise and, due Coulomb blockade,mediate supercurrent coherent co-tunneling of Cooper pairs. show resulting from such events exhibits, for low moderate fields, phase offset discriminates even and odd charge ground states on island. Notably,this persists when state approaches zero energy...
Three-dimensional magnetic null points (3D nulls) are sites of dynamic activity in a wide range naturally-occurring and laboratory plasma environments. The topology 3D is defined by two-dimensional fan plane radial field lines one-dimensional, collimated spine axis. Here, we build on previous work that was able to form an extended using assembly circular conducting coils, with each coil carrying constant current. While design decayed from the mathematically pure away central null, this paper...
Strain solitons are quasi-dislocations that form in van der Waals materials to relieve the energy associated with lattice or rotational mismatch crystal. Novel and unusual electronic properties of strain have been both predicted observed. To date, only observed exfoliated crystals mechanically strained bulk crystals. The lack a scalable approach towards generation poses significant challenge study use solitons. Here we report formation epitaxial growth bismuth on an InSb (111)B substrate by...
The surface and bulk states in topological materials have shown promise many applications. Grey or $\alpha$-Sn, the inversion symmetric analogue to HgTe, can exhibit a variety of these phases. However there is disagreement both calculation experiment over exact shape bands number origin states. Using spin- angle-resolved photoemission we investigate electronic structure $\alpha$-Sn thin films on InSb(001) grown by molecular beam epitaxy. We find that no significant warping shapes bands. also...
InAs quantum wells (QWs) grown on InP substrates are interesting for their applications in devices with high spin-orbit coupling (SOC) and potential role creating topologically nontrivial hybrid heterostructures. The highest mobility QWs limited by interfacial roughness scattering alloy disorder the cladding buffer layers. Increasing QW thickness has been shown to reduce effect of both these mechanisms. However, current state-of-the-art As-based barrier layers, critical is $\leq7$ nm. In...
The interplay between half-metallic ferromagnetism and spin-orbit coupling within the inversion symmetry-broken structure of half Heuslers provides an ideal platform for various spintronics functionalities. Taking advantage good lattice matching, it is highly desired to epitaxially integrate promising into III-V semiconductor-based devices. PtMnSb one first predicted be above-room-temperature half-metal with large spin orbit coupling, however, its half-metallicity potential as a material has...
High In content InGaAs quantum wells (In $\geq$ 75%) are potentially useful for topological computing and spintronics applications. high mobility wells, alloy disorder scattering is a limiting factor. this report, we demonstrate that by growing the as digital alloy, or short period superlattice, can reduce within well increase peak 2 K electron to 545,000 cm^2/V s, which highest reported best of authors' knowledge. Our results approach be used in random ternary materials.