Big data, bigger magnets, and tiny high-temperature superconducting cuprates

This work focuses on high magnetic field studies of the high-temperature cuprate superconductor YBa₂Cu₃O_y (YBCO) and associated data processing. YBCO is of much interest due to its high critical temperature (>90 K) and complex phase diagram containing many exotic phases. This work makes use of high magnetic fields (>30 T) to suppress the superconductivity and access under-explored parts of this phase diagram. The region of particular interest in this work is around 12 % hole doping where there is the charge density wave (CDW) region. The CDW is an ordered electronic state which has a large overlap with the high-temperature superconducting dome. In this region and on its periphery there are non-ohmic, quantum critical, and phase competition behaviours. To explore and disentangle these various effects, many high-field measurements have been taken over a range of temperatures, magnetic fields, applied currents, and hole dopings. The main focus of this work is developing and applying data processing methods to collate and explore these measurements to the fullest. Through the collection of many analysis steps and their visualisation into a single pipeline, synergies appear allowing consistent treatment across large datasets. From this, contour maps can be produced allowing mapping of the phase diagram using a variety of metrics. From the application of these techniques, three areas of enquiry stand out. Firstly, the superconductivity in YBCO extends to unexpectedly high applied magnetic fields at the lowest temperatures, and this is examined by studying the non-ohmic behaviour to understand the vortex dynamics. Secondly, the extent of the CDW in YBCO seems to vary on measurement technique indicating changing dynamics with temperature. Finally, the end of the CDW dome has been associated with quantum criticality and is further explored with magnetotransport measurements.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2022

Author dc:creator

• Hickey, Alexander

Advisor dc:contributor.advisor

• Grosche, Malte

• Data Processing
• High magnetic field
• High-temperature supercondtor
• Magnet
• Python
• YBCO

Licence

• https://www.repository.cam.ac.uk/bitstreams/bd751541-5d5e-4407-bd93-cca309103089/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.105672

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/363748