Condensed Matter Seminar

Abstract: TBA

Abstract: TBA

Abstract: TBA

Beyond Conventional Spin Models

• Example: High-spin d^7 Co2+ as an example of spin-orbit-entangled magnetism in a 3d system.
• Example: Kramers and non-Kramers doublets; dipolar-octupolar degrees of freedom in quantum spin-ice pyrochlores.
• Special case: Spin-only moments (d^5, f^7); connections to altermagnets and spin-orbit-free magnetism.
• Special case: Spin-orbital models, Kugel-Khomskii models

From Electrons to Exchange Interactions

• Hubbard-like models and superexchange; degenerate perturbation theory.
• Orbital and Hund's-coupling effects; Goodenough-Kanamori rules.
• Ligands, covalency, and charge-transfer processes.
• Anisotropy from spin-orbit coupling: Heisenberg, Dzyaloshinskii–Moriya, and symmetric anisotropic exchange.

From Atoms to Magnetic Moments

• The three scales: Coulomb interactions, spin-orbit coupling, and crystal fields; multiplets, Hund's rules
• Hierarchy of energy scales in 3d, 4d/5d, and 4f systems.
• Low-energy degrees of freedom: downfolding into spin, spin-orbital, or effective-spin models.
• Orbital quenching, spin-orbit-entangled moments, and crystal-field doublets.

Abstract: Artificial Intelligence (AI) is rapidly reshaping almost every aspect of our life, just as how lithium-ion battery did about four decades ago. As a special application of AI, AI4Science represents a fundamental shift in how research is conducted, accelerating discoveries across nearly every scientific domain, from materials design to system data analysis, from image processing to manufacturing control, and eventually the fully autonomous laboratories.

Abstract: The driven-dissipative many-body systems remain one of the most challenging unsolved problems of quantum physics. When “body” is spin, such as of electrons or of engineered ones like qubits, these many-body systems underlie spintronics, magnonics and quantum computing technologies. In this talk, I first explain conditions [1] under which quantum spins interacting with a dissipative environment can transition toward classical dynamics governed by the celebrated Landau-Lifshitz-Gilbert (LLG) equation.

Abstract: In frustrated magnetic systems with a subextensive number of classical ground states, quantum zero-point fluctuations can select a unique long-range ordered state, a celebrated phenomenon referred to as order by quantum disorder (ObQD). For frustrated spin-1/2 models, unbiased numerical methods able to expose ObQD are necessary. We show that ObQD can be identified from exact diagonalization calculations through an analysis akin to the Anderson tower of states associated with spontaneous symmetry breaking.

Abstract: Geometrically frustrated antiferromagnets are leading candidates for realizing quantum spin liquid (QSL) states. While there is a consensus on the existence of a QSL phase, its precise nature remains largely under debate. In this talk, I will argue that the situation is more intricate: multiple competing states can arise in the QSL-relevant regime with distinct dynamical spectral signatures. This behavior is robust across different cluster sizes, suggesting the persistence of these competing states towards the thermodynamic limit.