### ITAMP Fellow | Harvard University

Imaging stress and magnetism at high pressures using a nanoscale quantum sensor | Francisco Machado

# Imaging stress and magnetism at high pressures using a nanoscale quantum sensor

S. Hsieh, P. Bhattacharyya, C. Zu, T. Mittiga, T. J. Smart, Francisco Machado, B. Kobrin, T. O. Höhn, N. Z. Rui, M. Kamrani, S. Chatterjee, S. Choi, M. Zaletel, V. V. Struzhkin, J. E. Moore, V. I. Levitas, R. Jeanloz, N. Y. Yao
Science (2019)
arXiv:1812.08796

#### Abstract

Pressure alters the physical, chemical and electronic properties of matter. The development of the diamond anvil cell (DAC) enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena ranging from the properties of planetary interiors to transitions between quantum mechanical phases. In this work, we introduce and utilize a novel nanoscale sensing platform, which integrates nitrogen-vacancy (NV) color centers directly into the culet (tip) of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging (~600 nm) of both stress fields and magnetism, up to pressures ~30 GPa and for temperatures ranging from $25-340~\mathrm{K}$. For the former, we quantify all six (normal and shear) stress components with accuracy $< 0.01~\mathrm{GPa}$, offering unique new capabilities for characterizing the strength and effective viscosity of solids and fluids under pressure. For the latter, we demonstrate vector magnetic field imaging with dipole accuracy $< 10^{−11}~\mathrm{emu}$, enabling us to measure the pressure-driven $\alpha \leftrightarrow$ phase transition in iron as well as the complex pressure-temperature phase diagram of gadolinium. In addition to DC vector magnetometry, we highlight a complementary NV-sensing modality using $T_1$ noise spectroscopy; crucially, this demonstrates our ability to characterize phase transitions even in the absence of static magnetic signatures. By integrating an atomic-scale sensor directly into DACs, our platform enables the in situ imaging of elastic, electric and magnetic phenomena at high pressures.