Placement Information
Year you started your placement
2014
Placement period
May – August, September – December
Supervisor’s name
Alexander Boris
Project Details
Overview
Many fundamental questions remain open about the mechanism of high temperature superconductivity (HTS) in layered copper oxides. One of the challenges is to understand the competition and coexistence of HTS with other broken symmetry ground states. An increasing amount of experimental data obtained in recent years can be regarded as strong evidence for spontaneous symmetry breaking in the pseudogap phase of the cuprates and indicates that the charge density wave instability competes with HTS.
Cation disorder adds a degree of complexity which makes it very hard to compare experimental results with theoretical models which typically ignore any form of disorder. Oxide Molecular Beam Epitaxy (MBE) provides thin films of HTS which can be grown in a layer-by-layer fashion and doped with atomically controlled distribution of cations. These asymmetrically delta-doped SLs have inherent broken inversion symmetry and substantially reduced Sr disorder, and hence could serve as the described HTS model system. We investigate samples with the composition [(LaO-SrO-CuO2)+N×(LaO-LaO-CuO2)]×M (δS-LCON), where N = 3…12 was chosen, and M was fixed such that the overall thickness of these superlattices (SLs) grown on (001) oriented SrLaAlO4 substrates is ~ 50 nm.
Project objectives
We apply terahertz (THz) transmittance spectroscopy to study charge carrier dynamics in δS-LCON. Our experimental approach is based on measurements of both the transmission coefficient and phase shift of the transmitted radiation. The Mach-Zehnder sub-mm interferometer utilizes powerful backward-wave oscillators (BWOs) and allows to determine the spectra of conductivity and permittivity of SLs in the frequency range 2 – 40 cm-1 at temperatures T = 2 – 300 K, and in an external magnetic field of up to 9T (Oxford Spectromag 4000). These measurements can provide necessary information about the superconducting state of δS-LCON (the superconducting gap energy and the superfluid density) at various periodicities of the SrO δ-doping atomic monolayers. At the same time the magnetic and structural properties of this system will be studied by low-energy muon spin rotation (LE-μSR), x-ray diffraction and reflectivity, resonant inelastic x-ray scattering (RIXS), and electron microscopy. Our concerted efforts might shed light on the proximity effects between the superconducting and antiferromagnetic CuO2 planes at the atomic level.
Research outcomes
Project status
Completed
Expected completion date
12/31/2014
AndrewYao – 2014 – Presentation
My Co-op Experience at MPI
Why did you apply for a placement with Max Planck Institute?
MPI is a very prestigious research institute. And working and living Europe is a great experience in itself.
What recommendations do you have for students who wish to participate in MPI-UBC exchange program?
Get prepared academically at school and embrace life in Europe with an open mind.
Tell us about your travels and cultural experiences in Germany and the rest of the Europe
In addition to a few cities in Germany, I’ve also traveled to Switzerland, Italy, the Czech Republic, and the Netherlands. I’ve also be learning German.
