Gap Structure of the Spin-Triplet Superconductor Sr2RuO4 Determined from the Field-Orientation Dependence of Specific Heat

TL;DR

This study investigates the superconducting gap structure of Sr2RuO4 by measuring specific heat under different magnetic field orientations, revealing 4-fold oscillations and evidence of multi-band superconductivity.

Contribution

First precise measurement of field-orientation dependent specific heat in Sr2RuO4 revealing detailed gap structure and multi-band effects.

Findings

Observed 4-fold oscillations in density of states

Identified gap modulation with a minimum along [100] direction

Provided evidence for multi-band superconductivity

Abstract

We report the field-orientation dependent specific heat of the spin-triplet superconductor Sr2RuO4 under the magnetic field aligned parallel to the RuO2 planes with high accuracy. Below about 0.3 K, striking 4-fold oscillations of the density of states reflecting the superconducting gap structure have been resolved for the first time. We also obtained strong evidence of multi-band superconductivity and concluded that the superconducting gap in the active band, responsible for the superconducting instability, is modulated with a minimum along the [100] direction.