Research

What Do We Do?

At the Spin+ Lab, we study how collective behavior emerges from interacting degrees of freedom in quantum materials.

Electron spin is at the center of much of our research. Yet in real materials, spin rarely acts alone. It interacts with charge, orbital, and lattice degrees of freedom, giving rise to complex magnetic structures, unconventional excitations, hybrid quasiparticles, and emergent phases。 The “+” in Spin+ represents these interactions. We use spin as a window into the broader many-body physics of quantum materials.

The physics we are interested in often becomes most interesting when spin interacts with something else.

Primary Experimental Probe: Neutron Scattering

In solids, multiple degrees of freedom—such as spin, charge, orbital, and lattice—are interrelated through electron correlations. To detect the emergent orders associated with these degrees of freedom, we must use probes that interact effectively with each. For example, the electronic band structure is commonly explored using ARPES, while neutron scattering is ideal for investigating magnetic structure and dynamics. Phonon excitations can be examined through techniques like neutron scattering, inelastic X-ray scattering (IXS), and Raman scattering. By combining these probes, we can gain a more comprehensive understanding of the electronic behaviors in strongly correlated systems.

Our primary focus is using neutron scattering spectroscopy to probe lattice and spin dynamics in these systems. Neutrons, having no charge and a spin of 1/2, are sensitive only to lattice vibrations (phonons) and magnetic excitations (magnons). Moreover, at typical interatomic distances (1Å–10Å), neutron energies are well-matched to the energy scales of these excitations (0.1~100meV), making them an ideal tool for such studies. Neutron interactions with matter are relatively weak and nearly linear, which has several important consequences:

1. The neutron cross-section directly reflects the internal correlations of the solid, modulated only by a constant related to neutron-matter interactions.

2. Neutron scattering minimally disturbs the system, such as avoiding significant sample heating, making it suitable for low-temperature measurements.

3. Neutrons penetrate deeply into materials, probing bulk properties rather than just surface layers, though this requires a significant amount of sample material.

Our neutron experiments range from diffraction measurements of magnetic order to inelastic measurements of spin and lattice excitations. We combine these measurements with theoretical modeling to extract microscopic interactions and understand the collective physics they generate.

Materials and Complementary Probes

Neutron experiments begin with the right material. Because many neutron measurements require sizable, high-quality single crystals, materials synthesis and characterization are an integral part of our research.

We combine neutron scattering with complementary experimental techniques—including optical spectroscopy, X-ray scattering, thermodynamic measurements, and magnetic and transport characterization—when they provide information inaccessible to neutrons alone.

Together, these approaches allow us to move from materials → microscopic interactions → collective excitations → emergent phenomena.