APS March Meeting Student Practice Talk Session
Silicon MOSFET quantum dots with simplified metal-gate geometry
Eduardo Barrera
Silicon (Si) CMOS spin qubits have become a promising platform for a future quantum information processor due to recent demonstrations of high fidelity single and two qubit gates [Veldhorst et. al., Nature 526.7573 (2015)], compatibility with industrial CMOS process and promising prospects for scalability. Typical Si spin qubits devices consist of gate-defined quantum dots, each defined by several metal gates, which pose a challenge to scaling the technology up. Hence, future designs of Si spin qubits will need to reduce the fabrication complexity and adopt a scalable design.
Here, we introduce a two metal-layer MOSFET quantum dot device that reduces the number of metal gates and simplifies the dot tune-up procedure. By performing electron counting measurements with a charge sensor, we determine that the accumulation gate defining the electron reservoir can tune the dot-reservoir tunnel rate by about 10 decades/V. Magnetospectroscopy measurements up to 6 T reveal electron spin filling in the few electron regime from which we estimate a valley splitting of about 290 μeV.
Probing interlayer magnetism and magnons in two-dimensional chromium trihalides
Bowen Yang
Probing interlayer magnetism and magnons in two-dimensional chromium trihalides
We study CrX3 (X =I, Br, Cl) in the atomically thin limit by incorporating them in vertical tunnel junctions with graphene electrodes. In this device geometry, we are able to characterize the interlayer magnetic coupling, tunnel magnetoresistance, magnetic anisotropy, as well as magnon excitations. I will discuss the results of these studies and show how the magnetic properties of 2D CrX3 are modified when changing the halogen atom.
Pump-probe spectroscopy of ultrathin 1T'-MoTe2
Tina Dekker
Type II Weyl semimetal candidate MoTe2 in bulk form undergoes a transition at ~250 K from the monoclinic phase (1T’-MoTe2) to the inversion-symmetry breaking, orthorhombic phase (Td-MoTe2). Previous transport and Raman measurements on thin MoTe2 flakes have shown a dimensionally driven transition to the orthorhombic phase at room temperature for flakes less than ~12 nm. Using femtosecond broadband pump-probe spectroscopy, we impulsively excited MoTe2 flakes of varying thickness that are protected from oxidation. The temporal evolution of the vibrational wave packet causes spectral modulations of electronic transitions. A probe pulse following the pump reveals any pump-induced time dependence of these signals, including oscillations of the initially excited coherent nuclear motion. Using some novel data analysis tools, and after background subtraction, we were able to follow characteristic phonon modes of each phase resolved in time and frequency domains.
If you are coming from the Laziridis Centre, take the 11:35am shuttle to RAC 1 and return on the 1:15pm shuttle. There will be a light lunch served.