Superconducting vortices carrying a temperature-dependent fraction of the flux quantum

Yusuke Iguchi; Ruby A Shi; Kunihiro Kihou; Chul-Ho Lee; Mats Barkman; Andrea L Benfenati; Vadim Grinenko; Egor Babaev; Kathryn A Moler

doi:10.1126/science.abp9979

Superconducting vortices carrying a temperature-dependent fraction of the flux quantum

Science. 2023 Jun 23;380(6651):1244-1247. doi: 10.1126/science.abp9979. Epub 2023 Jun 1.

Authors

Yusuke Iguchi^{1

2}, Ruby A Shi^{1

2

3}, Kunihiro Kihou⁴, Chul-Ho Lee⁴, Mats Barkman⁵, Andrea L Benfenati⁵, Vadim Grinenko⁶, Egor Babaev⁵, Kathryn A Moler^{1

2

3

7}

Affiliations

¹ Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA.
² Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA.
³ Department of Physics, Stanford University, Stanford, CA 94305, USA.
⁴ National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan.
⁵ Department of Physics, Royal Institute of Technology, SE-106 91 Stockholm, Sweden.
⁶ Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 201210, China.
⁷ Department of Applied Physics, Stanford University, Stanford, CA 94305, USA.

PMID: 37262195
DOI: 10.1126/science.abp9979

Abstract

Magnetic field penetrates type-II bulk superconductors by forming quantum vortices that enclose a magnetic flux equal to the magnetic flux quantum. The flux quantum is a universal quantity that depends only on fundamental constants. In this study, we investigated isolated vortices in the hole-overdoped Ba_1-_xK_xFe₂As₂ (x = 0.77) by using scanning superconducting quantum interference device (SQUID) magnetometry. In many locations, we observed objects that carried only part of a flux quantum, with a magnitude that varied continuously with temperature. We demonstrated mobility and manipulability of these objects and interpreted them as quantum vortices with nonuniversally quantized (fractional) magnetic flux whose magnitude is determined by the temperature-dependent parameters of a multicomponent superconductor.