Topics

Quantum materials represent a very broad and fast-moving field, with new properties being discovered every day. At QuILL, we focus on quantum materials that exhibit unusual topology, quantum magnetism, and quantum transport of electrons.

Electronic Band Topology: Topology is a mathematical concept that categorizes objects by their geometrical properties (e.g., number of holes). Similarly, topological band theory categorizes electronic bands in materials by global quantum geometric invariants. We investigate topological materials including topological insulators, Dirac semimetals, and Weyl semimetals, where non-trivial topology yields quantized electrical conductance, robust boundary states, and protected surface Fermi arcs.

Quantum Magnetism: We explore the rich interplay between electronic topology and broken time-reversal or inversion symmetries. In non-centrosymmetric magnetic Weyl semimetals, for example, chiral Weyl electrons can mediate unconventional Ruderman–Kittel–Kasuya–Yosida (RKKY) exchange interactions, stabilizing chiral magnetic textures.

Quantum Transport: Coupling topology with lattice vibrations and electronic correlations can lead to unconventional collective behaviors. When momentum-conserving electron-phonon or electron-electron scattering dominates over momentum-relaxing mechanisms, electrons flow collectively like a viscous fluid, leading to exotic hydrodynamic transport behavior (Nat. Commun. 12, 5292).

Scaling quantum computers and next-generation high-performance computing requires a robust cryogenic electronics infrastructure. We develop energy-efficient cryogenic electronic devices designed for quantum information processing, data storage, and extreme environments such as outer space.

Superconducting Diode & Non-Reciprocal Electronics: Standard semiconductor electronics generate substantial thermal loads that overwhelm cryogenic systems. Analogous to semiconductor p-n diodes, superconducting diodes break spatial inversion and time-reversal symmetries to rectify supercurrents. This asymmetry yields non-reciprocal critical currents, allowing zero-resistance, dissipationless current flow in the forward direction while resisting transport in the other. The non-reciprocity forms the foundation for cryogenic rectifiers, switches, and non-volatile memory using superconducting diodes.

Multiferroic Josephson junction: Our recent work highlights the importance of improving functionalities in supercurrent diodes. By integrating 2D multiferroics into Josephson junctions, we realize field-resilient, non-volatile superconducting diodes (Nat. Commun. 16, 9287).

Topological quantum computing leverages the non-local properties of topological states to store and process quantum information with built-in protection against decoherence. We design and fabricate hybrid van der Waals heterostructures to realize and manipulate topologically protected quantum states.

Hardware-Level Topological Protection: Unlike conventional superconducting or semiconductor qubits that store state variables locally, topological qubits encode quantum information non-locally across spatially separated pairs of Majorana zero modes (MZMs). Because local environmental perturbations cannot alter this non-local state, topological qubits possess fundamentally enhanced coherence times without massive error-correction overhead. Moreover, since quantum logic operations in topological platforms are executed by exchanging ("braiding") the real-space positions of MZMs, these operations are also intrinsically resilient to control errors.

Zero-Field Topological Platforms: A longstanding bottleneck in topological quantum hardware is the requirement of high external magnetic fields, which degrade superconductivity and hinder scaling. By coupling topological superconductor candidates with ferromagnetism at atomically sharp interfaces, our work establishes a route to potentially induce MZMs under zero external magnetic field (Nat. Commun. 14, 6691).