Josep Ingla-Aynés

Spin–charge interconversion provides the essential link between spin information and electrical signals in spintronic devices. In spin–orbit coupled systems, spin–charge interconversion can contain multiple components associated with different spin-polarization directions, reflecting the underlying spin texture. Tuning this spin texture, therefore, provides a way to control not only the magnitude of spin–charge interconversion but also the balance among its different components. Graphene-based van der Waals heterostructures provide an attractive platform for this purpose because interfacial spin–orbit coupling can host multiple spin–charge interconversion channels that couple to different spin-polarization directions. Here, we demonstrate electric-field control of spin texture in a dual-gated HfS2/graphene van der Waals heterostructure, where independent control of carrier density and vertical electric field allows us to disentangle electrostatic doping from electric field-induced spin–orbit effects. Nonlocal spin precession measurements show that, near zero vertical electric field, spin–charge interconversion is dominated by a spin Hall component with out-of-plane spins. Increasing the vertical electric field enhances additional in-plane spin components with Rashba–Edelstein-like character, including contributions both parallel and perpendicular to the charge current. These results provide experimental evidence that a vertical electric field can reconfigure the effective spin texture and control the corresponding spin–charge interconversion components, demonstrating electrical tunability of spin–orbit functionalities.

The interaction between itinerant electrons and localized spins is key to a wide range of electronic phenomena. We present conductance measurements of a quantum point contact (QPC) in bilayer graphene (BLG). Beyond the expected quantized conductance plateaus reflecting spin-and-valley degeneracy, we observe an additional plateau resembling the “0.7 anomaly”, exhibiting signatures of Kondo physics, with a Kondo temperature ranging from approximately 0.5 up to well above 5 K at zero magnetic field, corresponding to energies between 43 and 430 μeV. Because the QPC is spin-and-valley degenerate within our experimental resolution (110 μeV), according to the prevailing Kondo model, these results are consistent with a transition between 4-fold degenerate SU(4) and 2-fold degenerate spin-valley locked SU(2) interactions. Furthermore, we break the degeneracy of the lowest subband by an out-of-plane magnetic field and show that Kondo signatures remain, demonstrating the versatility of BLG QPCs.

Altermagnets featuring collinear magnetic order and momentum-space spin splitting are a newly identified class of magnetically ordered materials. Most studies so far on altermagnetism focus on quasi-3D (e.g., > 10 nm) systems with bulk symmetry-dominance, while the quasi-2D regime with symmetry-breaking remains largely unexplored. Here, we report a pronounced anomalous Hall effect and tunable spin anisotropy arising from symmetry-breaking of the altermagnetic order in CrSb (2.4 nm)/(Bi _{1- x} Sb _x ) ₂ Te ₃ heterostructures. The anomalous Hall effect strength, driven by the modulation of altermagnetic spin texture orientation, can be tuned through strain via controlling the thickness and Fermi level of the topological insulator (Bi _{1- x} Sb _x ) ₂ Te ₃ . The effective Hamiltonian model reveals that the exchange coupling between the altermagnetic order and topology can produce a unique hybrid anomalous Hall effect. Angle-dependent magneto-transport investigation uncovers the magnetic dynamics of altermagnetic moments with exchange coupling. Our strategy broadens the way to explore altermagnetic interfacial physics and topological spintronics in quasi-2D altermagnet/topological insulator heterostructures.

As computing power demands continue to grow, superconducting electronics present an opportunity to reduce power consumption by increasing the energy efficiency of digital logic and memory. A key milestone for scaling this technology is the development of efficient superconducting memories. Such devices should be nonvolatile, scalable to high integration density and memory capacity, enable fast and low-power reading and writing operations, and be compatible with the digital logic. We present a versatile device platform to develop such nonvolatile memory devices consisting of an exchange-coupled ultra-thin superconductor encapsulated between two ferromagnetic insulators (FIs). The superconducting exchange coupling, which is tuneable by the relative alignment between the FI magnetizations, enables the switching of superconductivity on and off. We exploit this mechanism to create a superconducting nonvolatile memory where single-cell writing is realized using heat-assisted magnetic recording, and explain how it can become a contender for state-of-the-art superconducting memories. Furthermore, below their critical temperatures, the memory elements show a marked nonreciprocity, with zero magnetic field superconducting diode efficiencies exceeding $\pm$60%, showing the versatility of the proposed devices for superconducting computing.

The interplay between magnetic order and electronic band structure in antiferromagnets has garnered increasing interest due to its potential for spintronic applications. While magnetic transitions have been shown to induce substantial band structure modifications in optical measurements, their influence on electronic transport remains poorly understood. In this work, we investigate the transport properties of CrSBr, a van der Waals antiferromagnetic semiconductor, over a wide range of carrier densities modulated by gate voltage. We observe a drastic contrast in magnetoresistance behavior between the low- and high-carrier density regimes. Through a combination of experiment and modeling, we identify magnetically driven carrier concentration modulation and mobility modulation as the dominant mechanisms governing magnetoresistance in the respective regimes. These findings advance the understanding of magnetoelectric transport in antiferromagnets and suggest promising routes for energy-efficient spintronic technologies in memory, logic, and sensing applications.

Van der Waals heterostructures (vdWHs) composed of transition-metal dichalcogenides (TMDs) and layered magnetic semiconductors offer great opportunities to manipulate the exciton and valley properties of TMDs. Here, we present magneto-photoluminescence (PL) studies in a WSe₂ monolayer (ML) on a CrSBr crystal, an anisotropic layered antiferromagnetic semiconductor. Our results reveal the unique behavior of each of the ML-WSe₂ PL peaks under a magnetic field that is distinct from the pristine case. An intriguing feature is the clear enhancement of the PL intensity that we observe each time the external magnetic field tunes the energy of an exciton in CrSBr into resonance with one of the optical states of WSe₂. This result suggests a magnetic field-controlled resonant energy transfer (RET) beyond other effects reported in similar structures. Our work provides deep insight into the importance of different mechanisms in magnetic vdWHs and underscores its great potential for light harvesting and emission enhancement of two-dimensional materials.

A promising approach to attain long-distance coherent spin propagation is accessing topological spin-polarized edge states in graphene. Achieving this without external magnetic fields necessitates engineering graphene band structure, obtainable through proximity effects in van der Waals heterostructures. In particular, proximity-induced staggered potentials and spin-orbit coupling are expected to form a topological bulk gap in graphene with gapless helical edge states that are robust against disorder. In this work, we detect the spin-polarized helical edge transport in graphene at zero external magnetic field, allowed by the proximity of an interlayer antiferromagnet, CrPS₄. We show the coexistence of the quantum spin Hall (QSH) states and magnetism in graphene, where the induced spin-orbit and exchange couplings also give rise to a large anomalous Hall (AH) effect. The detection of the QSH states at zero external magnetic field, together with the AH signal that persists up to room temperature, opens the route for practical applications of magnetic graphene in quantum spintronic circuitries.