Distinguishing dxz + idyz and dx2−y2 pairing in Sr2RuO4 by high magnetic field H-T phase diagrams

DOI: https://doi.org/10.1103/PhysRevB.106.115126 Employing a realistic tight-binding model describing the Fermi surface in the normal state ofSr2RuO4 we map out magnetic field versus temperature phase diagrams for dx2−y2 (B1g) and dxz +idyz (Eg) pairing types. Both produce (i) a similar Knight shift suppression of ∼ 80% and (ii) abicritical point at T = 0.88K separating low field second order phase transitions from high fieldPauli limiting first order transitions. We find, however, strikingly different phase behaviour withinthe high field Pauli limiting region. For dx2−y2 pairing symmetry an additional lower critical lineof first order transitions is found (terminating in a critical point at T = 0.09 − 0.22K dependingon the choice of Hubbard U parameters) while for dxz + idyz no such additional high field phasetransitions are found for any choice of Hubbard U. In conjunction with our earlier finding [PhysicalReview B 102 (23), 235203] for p-wave helical pairing of a still different high field phase structure (alower critical field line meeting the upper critical field line exactly at the bicritical point), we suggesthigh field Pauli limiting phase structure as a possible route to distinguish pairing symmetries in thismaterial.