Measuring superconducting arcs by angle-resolved photoemission spectroscopy

Angle-resolved photoemission spectroscopy is the leading tool for studying the symmetry and structure of the order parameter in superconductors. The recent improvement of the technique made it possible to detect the superconducting energy gap at the surface of topological t- <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:msub> <a:mi mathvariant="normal">PtBi</a:mi> <a:mn>2</a:mn> </a:msub> </a:math> via observation of the record-breaking narrow line shapes. The promising new physics uncovered requires further investigation of the spectral and gap functions of t- <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:msub> <c:mi mathvariant="normal">PtBi</c:mi> <c:mn>2</c:mn> </c:msub> </c:math> , but the challenging experimental conditions severely limit the application of conventional ARPES setups. In this work, we use synchrotron-based measurements and show that the gap at the surface Fermi arc in t- <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:msub> <e:mi mathvariant="normal">PtBi</e:mi> <e:mn>2</e:mn> </e:msub> </e:math> can be detected even with more relaxed experimental conditions than in our previous laser-based studies. At the same time, using simple model of ARPES spectra, we identify the minimum requirements to detect the gap and consider cases where the gap cannot be resolved.