Looking Forward

Conclusion

In this experiment, the Integer Quantum Hall effect was measured in bilayer graphene. Although plateaus in the Hall resistance were observed, they were impossible to analyzed because non-integer plateau values were observed. The two wire measurement configuration used limited the accuracy of the measurement, because a combination of the Hall resistance and the longitudinal resistance were measured. A better configuration is a four point measurement that separates the the Hall and longitudinal resistance. Raw data from four point measurements of the Integer Quantum Hall effect in monolayer graphene were provided by graduate student's in Ke Wang's lab. We analyzed this data, and extracted a value for Planck's constant of:

This was 0.4% off from the accepted value of Planck's constant. The difference in standard deviations was 5.3 . It is possible that systematic errors introduced by assuming the current through the sample was 10 nA.

Improvements for Future Projects

The most obvious improvement is to do the four point measurement as part of the experiment. The two point measurement was chosen because it was took less time to prepare the contacts. Although there is a limited amount of time in the semester, a four point measurement could be prepared. We thought we behind when the sample was prepared, but we ended up having data well before the end of the semester.

Another idea is to try to observe the Quantum Hall effect in other materials. Graphene is a simple 2D material, which is why it was chosen, but it is also possible to observe the Quantum Hall effect in other 2D materials.

Acknowledgements

Many thanks to Professor Ke Wang for advising us on this project, and to Kan-Ting Tsai and Yujie Luo for their invaluable assistance throughout the semester. We would also like to thank Professor Crowell for allowing us to use his PPMS in this project.

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