Exploring Quantum Sensing in the Megabar Range
In a groundbreaking development, a team of researchers has unveiled a revolutionary quantum sensing approach that is poised to transform our understanding of superconductivity at extreme pressures. Led by Prabudhya Bhattacharyya and colleagues, this innovative study has shed new light on the elusive Meissner effect in hydride superconductors, a long-standing challenge in the quest for room-temperature superconductivity.
The pursuit of high-temperature superconductors has taken a fascinating turn in recent years, with a growing focus on materials subjected to immense pressures. Theoretical predictions have suggested that the strong electron-phonon coupling and high characteristic phonon frequencies in hydrogen-rich compounds could stabilize superconducting states at temperatures as high as 300 Kelvin under megabar conditions.
However, probing the magnetic signatures of these superconducting phenomena has proven to be a daunting task for conventional experimental techniques. The sensitivity limitations of magnetic sensors at such extreme pressures have hindered the direct observation of the Meissner effect, a hallmark of superconductivity.
Bhattacharyya and colleagues have now overcome this challenge by harnessing the extraordinary sensitivity of nitrogen-vacancy (NV) centers – defects in the diamond lattice that are exquisitely responsive to magnetic field variations. By carefully protecting the intrinsic symmetry of the NV structure, the team has demonstrated enhanced sensitivity and high-contrast magnetic field measurements, even in the face of the extreme pressures involved.
Using this innovative quantum sensing approach, the researchers were able to directly monitor the local magnetic response in samples of a recently discovered cerium hydride superconductor at pressures up to 140 gigapascals (GPa). To their delight, they observed distinct local field expulsion signatures, clear evidence of the Meissner effect, and directly imaged the micron-scale inhomogeneities in the superconducting regions.
Complementary resistance measurements confirmed the bulk superconducting transition, and further exploration of magnetic field and thermal cycling unveiled temperature-dependent hysteresis and flux trapping behavior, reminiscent of a disordered superconductor. Interestingly, the team also observed differences from canonical expectations, such as a sharp transition for certain magnetic field amplitudes, hinting at the complexity of these high-pressure systems.
This groundbreaking work establishes NV-based quantum sensing as a powerful tool in the megabar frontier, paving the way for the optimization of superhydride synthesis and the nano-imaging of magnetism, charge, and lattice dynamics at unprecedented pressures. As the scientific community continues to push the boundaries of our understanding of superconductivity, this study stands as a shining example of the transformative potential of quantum sensing technologies.
Source: https://www.nature.com/articles/s41567-024-02485-1
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