Monthly Archives: November 2024

Andrea Maiani (26/11/24)

Sin categoría

Andrea Maiani

WINQ Postdoctoral fellow, Nordita.

 

Impurity States in Altermagnetic Superconductors

When: 12:00-13:00 CET, November 26th (Tuesday), 2024

Where: Sala de Seminarios (182), ICMM-CSIC, Campus de Cantoblanco, Madrid

 

Altermagnets are a novel class of magnetic materials distinct from ferromagnets and antiferromagnets, characterized by vanishing net magnetization and unique spin-split band structures – appealing features for exotic quantum phenomena and spintronics applications. This talk explores the interplay between altermagnetism and superconductivity, focusing on how impurities can serve as local probes of altermagnetic superconductors. I will briefly introduce altermagnetic materials, their interplay with superconductivity, and review the basic theory of impurity states in superconductors. I will then present our original theoretical work on the role of impurities in altermagnetic superconductors, predicting the emergence of spin-polarized subgap states that extend along the crystal axes. These states form degenerate doublets, which can be split by crystal symmetry breaking or a magnetic field aligned with the Néel vector. Their unique spatial and spin properties provide measurable signatures via scanning tunneling microscopy, serving as a hallmark for altermagnetic superconductivity. Finally, I will discuss the interaction between impurities, revealing a position-dependent, spin-selective coupling that enables in-situ control of devices crucial for quantum information processing and topological superconductivity.

Natalia Berloff (07/11/24)

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Natalia Berloff

Department of Applied Mathematics and Theoretical Physic, University of Cambridge, UK

Non-Hermitian Gain-Based Computing with Coupled Light-Matter Systems 

When: 12:00-13:00 CET, November 7th (Thursday), 2024

Where: Sala de Seminarios (182), ICMM-CSIC, Campus de Cantoblanco, Madrid

Gain-based computing utilizing non-Hermitian dynamics in light-matter interactions presents a novel approach to physics-based hardware and physics-inspired algorithms. By encoding complex optimization problems into the gain and loss rates of driven-dissipative systems, we leverage non-Hermiticity to destabilize non-optimal states and guide the system toward the global minimum. The incorporation of prior knowledge about ground state energies into the complex part of the energy enhances the system’s ability to navigate complex energy landscapes.
In this paradigm, the system undergoes symmetry-breaking transitions on a dynamically changing loss landscape, selecting modes that minimise losses and manifesting the optimal solutions to the original problems. This approach enables solving significant combinatorial optimization problems via mapping to Ising, XY, and k-local Hamiltonians, applicable across various physical platforms, including photonic, electronic, and atomic systems.
 Despite advancements, critical questions remain regarding scalability, the impact of phase space structures on system performance, and the identification of problems best suited for these unconventional computing architectures. I will address these challenges in my talk by understanding the dynamic behaviour during symmetry-breaking transitions, optimizing trajectories toward global minima, quantifying error probabilities, and using dissipation and nonlinearities to correct errors.