Theoretical studies for identifying horizontal line nodes via angle-resolved density-of-states measurements: Application to Sr2RuO4

Abstract

On the basis of the microscopic quasi-classical Eilenberger theory, we analyze the recent angle-resolved specific heat experiment carried out at low temperature for Sr 2 RuO 4 to identify the superconducting gap symmetry, comprising either horizontal or vertical line nodes relative to the tetragonal crystal symmetry. Several characteristics, in particular, the landscape of the in-plane oscillation amplitude A 4 (B, T) with a definite sign for almost the entire B-T plane are best explained by the horizontal line node symmetry, especially when the multiband effect and Pauli paramagnetic effect are taken into account. The present analysis of A 4 (B, T) with definite sign points to the presence of an anomalous field region at a lower temperature in the experimental data, whose origin is investigated. Our theory demonstrates the application and uniqueness of the field-rotating thermodynamic measurements in uncovering the precise gap structure for target materials.

Horizontal Line Nodes in Sr2RuO4 Proved by Spin Resonance

“…2e). We address that the observed L modulated intensity cannot be explained by the superconducting gaps with the vertical line nodes 29 . On the other hand, any pronounced L modulation at higher energy transfers are observed neither in the experiment (Fig.…”

“…L dependence of the low-energy IC magnetic fluctuations provides us the compelling evidence to clarify the line nodes at the superconducting gaps 29 . Contour maps of the INS intensities in the (HHL) plane at 0.3 K with the energies 0.35, 0.56, and 0.74 meV are illustrated in Fig.…”

“…Recently, time-reversal invariant superconductivity in Sr2RuO4 is proposed by the Josephson effects 42 . Combined with the time-reversal invariant superconductivity and the horizontal line nodes, dwave 𝑑 3𝑘 𝑧 2 −1 29 or nodal s' is proposed for the candidate for the pairing symmetry of Sr2RuO4.…”

“…vertical or horizontal, are not uncovered yet. The thermal conductivity measurements reported vertical line nodes on the superconducting gaps 27 , whereas field-angle-dependent specific heat capacity measurements reported the horizontal line nodes 28,29 . Since the complete information of the superconducting gaps can shed light on the pairing symmetry, exclusive determination of the direction of the line nodes in Sr2RuO4 is now called for.…”

Microscopic Eilenberger theory of Fulde-Ferrell-Larkin-Ovchinnikov states in the presence of vortices

“…(5) Sr 2 RuO 4 , which was a prime candidate of a chiral p wave superconductor 28,29 , but recent various theoretical and experimental studies [30][31][32] indicate now that it is most likely to be a spin singlet superconductor. Since the system well satisfies the necessary conditions for the LO to appear.…”