Visualizing the magnetic-field induced melting of the charge density wave in UTe₂

UTe₂ is a heavy fermion superconductor that has gathered a lot of interest in the family of strongly correlated, unconventional superconductors in the recent years. Subsequent work on this material has shown the presence of a coexisting charge-density wave (CDW) order which is strongly intertwined with superconductivity (1,2). The charge density wave has an unconventional character due to its magnetic-field sensitivity, particularly the disappearance of the CDW order at superconducting H_c2. One possible explanation for this behavior invokes the presence of a pair density wave state (PDW). The PDW scenario suggests that any vortex in the uniform superconducting phase or the PDW phase will result in topological point defects i.e., dislocations in the CDW. In this talk, I will describe our work employing scanning tunneling microscopy (STM) to visualize the magnetic field induced melting of this unconventional CDW order through amplitude and phase maps from the Fourier transforms. Using the phase maps, we can identify the presence of topological defects (dislocations in the CDW) with opposite phase winding. We show that the number of these topological defects increases with increasing magnetic field and that these defects are directly responsible for destroying the CDW order. This is consistent with the existence of a PDW state in this strongly correlated superconductor.

References

1.Aishwarya, A. et al, Nature, 618, 7967 (2023).

2.Gu, Q. et al, Nature, 618, 7967 (2023).