Field Angle Tuned Metamagnetism and Lifschitz Transitions in UPt3

Magneto Acoustic Quantum Oscillations in High Fields and the Fermi Surface of UPt$_3$

“…The small size of this FS leads to large MAQO in the ultrasound data for reasons discussed above. As explained in our previous work 13 , the change of this tiny pocket of the FS is responsible for the LT at 24.8 T and 30 T. Although the most significant difference between low and high field measurements is seen for the δ and γ orbit, we observe most other orbits predicted by existing band structure calculations on both sides. These orbits along the a-axis as well as the c-axis show no significant change with field, although some of the orbits appear at a slightly different frequency.…”

“…The low field dip at 8 T was assigned by Bruls et al 18 to a spin-density wave (SDW) transition. The high field dip at 30 T recently discovered by us can similarly be attributed as a transition to another SDW state 13 . As discussed in that work a separate background subtraction procedure is employed to make the MAQO stand out for this orientation.…”

“…We also observe the orbits seen in previous dHVa and Shubnikov de Haas measurements [10][11][12] . In addition, a change in the FS related to the metamagnetic transition in UPt 3 at 20 T along the a-axis is seen as well as changes in frequency across the Lifshitz transitions at 24.8 T and 30 T along the c-axis discovered by us recently 13 . The measurements we report were performed on zone refined single crystals of approximately 3 mm x 3mm x 2.5 mm grown at Argonne National Labs and of the same quality as those employed in previous ultrasound work 14 .…”

“…8. The MMT is not crossed here 13 and hence the orbit survives in the highest fields. Therefore, the disappearance of this sheet of the FS is the primary cause of the metamagnetism in UPt 3 .…”