A Study of Magnetism and Possible Mixed-State Superconductivity in Phosphorus-Doped Graphene

Authors

Julian E. Gil Pinzon, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Electrical and Computer Engineering

First Advisor's Name

Grover Larkins

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Jean Andrian

Second Advisor's Committee Title

Co-Committee chair

Third Advisor's Name

Yuriy Vlasov

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Nezih Pala

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Pete Markowitz

Fifth Advisor's Committee Title

committee member

Keywords

Phosphorus-doped graphene, Mixed-state superconductivity, High-temperature superconductivity, Hysteresis

Date of Defense

6-29-2021

Abstract

Evidence of superconducting vortices, and consequently mixed-state superconductivity, has been observed in phosphorus-doped graphene at temperatures as high as 260 K. The evidence includes transport measurements in the form of resistance versus temperature curves, and magnetic measurements in the form of susceptibility and magnetic Nernst effect measurements. The drops in resistance, periodic steps in resistance, the appearance of Nernst peaks and hysteresis all point to phosphorus-doped graphene having a broad resistive region due to flux flow as well as a Berezinskii-Kosterlitz-Thouless (BKT) transition at lower temperatures.

The observation of irreversible behavior in phosphorus-doped graphene under the influence of a thermal gradient and an orthogonal applied magnetic field is a direct sign of mixed-state superconductivity, as it demonstrates the presence of vortices. The observations are based on cyclic Nernst measurements that show clear hysteresis that diminishes as the sample is warmed to temperatures higher than 200 K; voltage steps and anomalous structures related to field screening are observed at temperatures below 70 K; and finally, smaller Nernst peaks are seen at temperatures near 230 K pointing to vortex stacks having a high depinning and thermal energies.

Identifier

FIDC010270

Previously Published In

Sornkhampan N., Gil-Pinzon J., Ponce-Zuniga J., Woods A., Vlasov Y., Larkins G., (2021). Evidence of vortices and mixed-state superconductivity in phosphorus-doped graphene. Part I (Nernst). Superconductor Science and Technology 34 035022

Gil-Pinzon J., Sornkhampan N., Woods A., Vlasov Y., Larkins G., (2021). Evidence of vortices and mixed-state superconductivity in phosphorus-doped graphene. Part II (Hysteresis). Superconductor Science and Technology 34 03502

K. Holland, "Doping as a Possible Means to create Superconductivity in Graphene," 2016.

N. Sornkhampan, "Study of Charge Carrier Transport in Graphene and Graphite as Two Dimensional and Quasi-Two Dimensional Materials and Their Interfaces," 2019.

Recommended Citation

Gil Pinzon, Julian E., "A Study of Magnetism and Possible Mixed-State Superconductivity in Phosphorus-Doped Graphene" (2021). FIU Electronic Theses and Dissertations. 4744.
https://digitalcommons.fiu.edu/etd/4744