Summer projects 2023
These projects are suitable for undergraduate students after their 3rd year once they have studied condensed matter physics concepts. To apply for these projects please send your CV and a cover letter to justify your interest in the proposed topic to amalia.coldea@physics.ox.ac.uk. Please also organize a letter of support from your tutor as part of your application.Funding will be sought as part of the EPSRC Vacation Internships. Students are always encouraged to find alternative sources of funding towards their summer projects.
Deadline: 7 March 2023
We are looking for enthusiastic students with good computational skills (Python, Matlab) and good understanding of condensed matter physics concepts. Good communication and time management skills are another important part for a successful interaction and progress in research. The experience gained during the summer project is transferrable to future projects towards MPhys and PhD projects in the area of Superconductivity and Quantum Materials. The projects will be performed in the new Oxford Centre for Applied Superconductivity (CfAS).
A. Torque magnetometry of novel superconductors
Torque magnetometry is a powerful technique to detect phase transitions and anisotropy of quantum materials and to investigate quantum oscillations in high magnetic fields which originated from their Fermi surface. Torque magnetometry uses highly sensitive piezocantilevers in which the change in the bending of the lever is related to the change in their resistance. These piezocantilevers are the most sensitive magnetometers that can probe very small changes in the magnetic moment up to a factor of 1000 smaller than any commercial magnetometer. In this project the student will perform torque measurements to characterize the behaviour of novel iron-based superconductors. The experiments will be performed as a function of temperature and in high magnetic fields up to 16T and the upper critical field phase diagram can be constructed. The student will perform data analysis using available Matlab software.
For further readings see:
https://aip.scitation.org/doi/10.1063/1.1491999
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.101.216402
https://arxiv.org/abs/2001.02434
B. Modelling vortex dynamics inside novel superconductors in magnetic fields
This project aims to understand the complex vortex dynamics inside two-dimensional superconductors in the presence of different defects and impurities. This is crucial for the implementation of high-temperature superconductors in applications as the vortex pinning on defects help to maintain very large critical currents. Simulations will rely on time-dependent Ginzburg Landau theory, which is already implemented in the commercial software package COMSOL Multiphysics. In this project, simulations of vortex lattice and relevant superconducting parameters will be perform using realistic parameters in order to understand the presence of large critical currents in novel iron-based superconductors. This project will be performed in the new Oxford Centre for Applied Superconductivity (CfAS).
A suitable candidate should have a strong background in condensed matter physics and strong computational skills, such as COMSOL, Matlab or Python. We are looking for candidates interested to pursue further projects in condensed matter physics.
To apply for this project please send your CV and a cover letter to justify your interest in the proposed topic to amalia.coldea@physics.ox.ac.uk.
For further reading see:
1.COMSOL Multiphysics https://www.comsol.com/comsol-multiphysis
2.https://www.comsol.com/blogs/modeling-superconductivity-ybco-wire/
4. See also the video of simulations on http://www.cfas.ox.ac.uk/discover
C. Critical currents of high-temperature superconductors
Superconductivity has a very large number of practical applications from superconducting magnets used in MRI scanners to levitating trains and its ultimate use is for reduction of the energy consumption as superconductors have zero resistance. To test realistic materials for potential applications one needs to know their phase diagrams, in particular of the critical current and the critical magnetic field. This project will explore the critical current as determined from magnetization measurements as well as from direct transport studies in high magnetic fields and at very low temperatures. The project aims to be able to predict superconducting phase diagrams of new superconductors based on the input parameters of different materials. This project can also make use of finite element software COMSOL to compare with experimental results.
For further information, please read:
Critical‐state magnetization of type‐II superconductors in rectangular slab and cylinder geometries Journal of Applied Physics 77, 3945 (1995)
http://dx.doi.org/10.1063/1.358576
Magnetization of Hard Superconductors,
Phys. Rev. Lett. 8, 250 (1962) https://doi.org/10.1103/PhysRevLett.8.250
Critical current and critical magnetic field in hard superconductors,
http://jetp.ac.ru/cgi-bin/dn/e_018_05_1368.pdf
D. Experimental studies and Instrument control using Python for experiments at ultra-low temperatures and high magnetic fields
This project aims to integrate new instrumentation and scripts for performing experiments as a function of temperature and high magnetic fields. We have developed over the years software both in Python or Matlab to run novel experiments on quantum materials. The next step is to intergate our software with the 21T magnet and Heliox eperiments to be able to perform experiments to probe novel states of quantum matter in high magnetic fields fdown to 0.3K and 21T. These systems will also be intergated with two-axis rotators for study of anisotropic properties of transport and thermodynamic properties.
E. Fermi surface topography of novel quantum materials
A Fermi surface is an essential concept to understand metallic and unconventional electronic states. Fermi surface can display beautiful and complex geometrical shapes that contains important information about the physical phenomena displayed by real materials. Among these, superconductivity is an instability of the Fermi surface in the presence of unconventional attractive interactions that cause pairing of electrons. The resulting superconducting gaps or the type of pairing is strongly linked to the details of the Fermi surface. Thus, in order to develop new models for superconductivity as well as to predict superconductivity at high temperatures one needs to be able to understand all essential ingredients of the electronic structure of a material.
This project is a computational and analytic study of the electronic structure of quantum materials in order to determine the exact topography of its Fermi surface. The student will use existing software in Matlab and further develop functions to predict the angular dependence of the Fermi surface and compare to available quantum oscillations data. Once the Fermi surface is fully determined the project can be extended to include predictions about the magnetotransport behaviour and specific heat.
For further details, please read:
The Key Ingredients of the Electronic Structure of FeSe
https://arxiv.org/abs/1706.00338, Annual Review of Condensed Matter Physics, Vol 9 (2018)
Emergence of the nematic electronic state in FeSe,
Phys. Rev. B 91, 155106 (2015), https://arxiv.org/abs/1502.02917
Detailed Topography of the Fermi Surface of Sr2RuO4,
Phys. Rev. Lett. 84, 2662 (2000), https://doi.org/10.1103/PhysRevLett.84.2662
https://arxiv.org/abs/0905.4844