2 research outputs found
Direct observation of altermagnetic band splitting in CrSb thin films
Altermagnetism represents an emergent collinear magnetic phase with
compensated order and an unconventional alternating even-parity wave spin order
in the non-relativistic band structure. We investigate directly this
unconventional band splitting near the Fermi energy through spinintegrated soft
X-ray angular resolved photoemission spectroscopy. The experimentally obtained
angle-dependent photoemission intensity, acquired from epitaxial thin films of
the predicted altermagnet CrSb, demonstrates robust agreement with the
corresponding band structure calculations. In particular, we observe the
distinctive splitting of an electronic band on a low-symmetry path in the
Brilliouin zone that connects two points featuring symmetry-induced degeneracy.
The measured large magnitude of the spin splitting of approximately 0.6 eV and
the position of the band just below the Fermi energy underscores the
signifcance of altermagnets for spintronics based on robust broken time
reversal symmetry responses arising from exchange energy scales, akin to
ferromagnets, while remaining insensitive to external magnetic fields and
possessing THz dynamics, akin to antiferromagnets.Comment: 10 pages, 7 figures (including supplementary information
Optical Trapping and Manipulation of Superparamagnetic Beads Using Annular-Shaped Beams
We propose an optical tweezers setup based on an annular-shaped laser beam that is efficient to trap 2.8 μ m-diameter superparamagnetic particles. The optical trapping of such particles was fully characterized, and a direct absolute comparison with a geometrical optics model was performed. With this comparison, we were able to show that light absorption by the superparamagnetic particles is negligible for our annular beam tweezers, differing from the case of conventional Gaussian beam tweezers, in which laser absorption by the beads makes stable trapping difficult. In addition, the trap stiffness of the annular beam tweezers increases with the laser power and with the bead distance from the coverslip surface. While this first result is expected and similar to that achieved for conventional Gaussian tweezers, which use ordinary dielectric beads, the second result is quite surprising and different from the ordinary case, suggesting that spherical aberration is much less important in our annular beam geometry. The results obtained here provide new insights into the development of hybrid optomagnetic tweezers, which can apply simultaneously optical and magnetic forces on the same particles