Agenda

Next Quantum Material Seminar:

Thursday, November 10th 2022 at 2pm

Klaus Hasselbach  (Institut Néel)

“Chiral Superconductivity in UPt3 observed by scanning SQUID Microscopy”

To access this seminar:

Institut Néel CNRS, Building E, 3rd floor, Room Louis Weil (E424)

Abstract:

Symmetry and topology are tools to describe states of quantum matter. A long sought after indication for unconventional pairing of superconducting electrons is the breaking of additional symmetries other than gauge symmetry.

UPt3 undergoes at low temperatures a strong electron mass renormalization (more than 100 times the free electron mass). These heavy fermions form Cooper pairs in the superconducting phase below 0.55 K. Superconductivity is expected to be mediated by spin fluctuations. UPt3 presents at ambient pressure three different superconducting phases A,B,C, each with an order-parameter of different symmetry. Upon cooling in zero applied magnetic field the frontier between the A and the predicted chiral B phase (breaking time reversal symmetry) is crossed at 0.5 K. In the B phase, energetically degenerate chiral domains are expected to appear. Theory foresees the existence of fractional vortices and an unusual magnetic flux distribution at the domain wall separating chiral domains.

With our scanning SQUID microscope we could observe in the B phase of UPt 3 magnetic flux aligning with domain walls and detect half-Ф0 vortices. Half-Ф0 vortices are not observed in the A phase. These direct observations are a strong indication for time reversal symmetry breaking and chiral superconductivity in UPt3.

The organizers:

Elsa Lhotel (elsa.lhotel@neel.cnrs.fr)
Florence Levy-Bertrand (florence.levy-bertrand@neel.cnrs.fr)