Recently, gate-defined Josephson junctions based on magic-angle twisted bilayer graphene (MATBG) have been fabricated. In such a junction, local electrostatic gating can create two superconducting regions connected by an interaction-driven valley-polarized state as the weak link. Due to the spontaneous time-reversal and inversion symmetry breaking, novel phenomena such as the Josephson diode effect have been observed with zero external magnetic fields. Importantly, when the so-called nonreciprocity efficiency (which measures the sign and strength of the Josephson diode effect) changes sign, the energy-phase relation of the junction is approximately F(ϕ) ∝ cos(2ϕ)where F is the free energy and ϕ is the phase difference of the two superconductors. In this work, we show that such a MATBG-based Josephson junction, when shunted by a capacitor, can be used to realize the long-sought-after 0-πqubits which are protected from local perturbation-induced decoherence. Interestingly, by changing the junction parameters to the regime where a large nonreciprocity efficiency is obtainable, transmon-like qubits with large anharmonicity can also be realized. The gate-defined Josephson junctions can be employed as platforms for realizing qubits that are protected from local perturbations.

Negative Differential Conductance (NDC) is a hallmark anomalous phenomenon in transport measurements, which is relatively rare in scanning tunneling microscopy due to its direct association with the local density of states. In this work, we constructed an ultrathin two-dimensional metal/semiconductor heterostructure by epitaxially growing a bilayer bismuth (Bi) film on a tin selenide (SnSe) substrate, revealing a unique moiré pattern arising from lattice mismatch. Spatially resolved tunneling spectroscopy detected a prominent NDC feature at approximately -650 meV. Both the energy position and depth of the NDC dip are strictly modulated by the periodicity of the moiré pattern. Our work not only establishes a novel Bi/SnSe material platform exhibiting NDC but also reports the visualization of NDC spatially modulated by a two-dimensional moiré superlattice, providing insight for the moiré electronics.

Topological wave-packet dynamics provide a powerful framework for studying quantum transport in topological materials. However, extending this approach to non-Hermitian quantum systems presents several important challenges, primarily due to ambiguities in defining the Berry phase and the non-unitary evolution of the wave-packets when symmetry is broken. In this work, we adopt the complex Berry phase definition using the bi-orthogonal formalism and derive the semiclassical equations of motion (EOM) for a wave-packet in a non-Hermitian topological system. Interestingly, we find that the complex Berry curvature introduces both an anomalous velocity and a non-Hermitian Hall-like force into the semiclassical EOM. To validate the derived EOM, we design a non-Hermitian Haldane model featuring non-reciprocal next-nearest-neighbor (NNN) hopping, where the imbalance in the NNN hopping amplitudes gives rise to an emergent 'complex chirality'. We reveal that the real and imaginary components of the complex chirality dictate the signs of both the real and imaginary parts of the complex Berry curvature, as well as the direction and dissipation rate of the edge states. Our analytical findings are confirmed by direct numerical simulations of the wave-packet dynamics. Finally, we suggest a potential experimental realization of this complex Haldane model using a non-Hermitian optical chiral cavity, providing a promising platform for testing our theoretical predictions.

Strong electron correlation drives 1T-TaS₂ from a half-filled metallic state into a Mott insulating phase, coexisting with a charge density wave at low temperatures. Under external stimuli such as pressure or ionic gating, superconductivity emerges in 1T-TaS₂, exhibiting an intricate relationship of competition and coexistence with the charge density wave order. In the two-dimensional (2D) limit, enhanced quantum fluctuations can stabilize a quantum spin liquid (QSL) state in the Mott insulator. This review summarizes recent advances in understanding these quantum states in 2D 1T-TaS₂ from the perspective of angle-resolved photoemission spectroscopy (ARPES)and scanning tunneling microscopy (STM), with a focus on the dimensionality effect on its electronic structure. We outline the signatures of QSL state in electronic spectra and discuss how this state can be revealed in the family of this material through experimental approaches beyond conventional probes such as neutron scattering. The role of Kondo effect in detecting spinon excitations is further discussed. Finally, we suggest future experimental directions and highlight how external perturbations such as gating and light excitation offer versatile pathways to control and exploit these intertwined quantum states.

Kagome materials have recently emerged as a versatile platform for exploring the intricate interplay among lattice, charge, spin, and orbital degrees of freedom, giving rise to a rich variety of quantum phenomena. While early studies predominantly focused on bulk kagome crystals, recent efforts have increasingly shifted toward their thin-film counterparts, motivated by the pursuit of enhanced tunability and potential device integration. Compared to bulk crystals, thin films offer distinct advantages such as precise control over strain, substrate-induced interactions, and reduced dimensionality, which together enable the modulation of electronic structures and the stabilization of emergent states. In particular, the ability to fine-tune key band features relative to the Fermi level provides a powerful route for engineering exotic states, including flat-band-driven magnetism, topological phases, and correlated electron phenomena. In this review, we provide a comprehensive overview of recent advances in the synthesis, characterization, and electronic structure studies of kagome thin films. We highlight key experimental breakthroughs that reveal how their topological and correlated properties evolve and discuss their broader significance within the landscape of quantum materials. Given the rapid convergence of experimental observations across diverse kagome systems, this review aims to offer timely guidance for future efforts toward unraveling the microscopic mechanisms of these unconventional electronic states.