Pramodh Senarath Yapa

PhD Student, Department of Physics, University of Alberta

Hello! My name's Pramodh (pronounced like Promote but with a d instead of a t ) and welcome to my mostly-about-research site! I study the physics of ultra-cold materials to understand how they tick at the quantum mechanical level; the specific systems I've looked at are superfluids, superconductors and Bose-Einstein condensates. You can find my CV here: download cv

I also spend a lot of time thinking about Science Communication and creative ways to reach the public (Hola, Dance Your PhD 2018!), so you can check that by navigating to the "SciComm" tab above or clicking HERE!

If you want a long - but very accessible - introduction to what I do every day, check out this video I made for the Morrin Centre in Quebec explaining the day-to-day of a theoretical condensed matter physicist:

Publications.

Triangular Pair-Density Wave in Confined Superfluid Helium-3

arXiv:2104.15125 – Submitted 30 April 2021

P. Senarath Yapa, R. Boyack, and J. Maciejko

Recent advances in experiment and theory suggest that superfluid 3He under planar confinement may form a pair-density wave (PDW) whereby superfluid and crystalline orders coexist. While a natural candidate for this phase is a unidirectional stripe phase predicted by Vorontsov and Sauls in 2007, recent nuclear magnetic resonance measurements of the superfluid order parameter rather suggest a two-dimensional PDW with noncollinear wavevectors, of possibly square or hexagonal symmetry. In this work, we present a general mechanism by which a PDW with the symmetry of a triangular lattice can be stabilized, based on a superfluid generalization of Landau's theory of the liquid-solid transition. A soft-mode instability at finite wavevector within the translationally invariant planar-distorted B phase triggers a transition from uniform superfluid to PDW that is first order due to a cubic term generally present in the PDW free-energy functional. This cubic term also lifts the degeneracy of possible PDW states in favor of those for which wavevectors add to zero in triangles, which in two dimensions uniquely selects the triangular lattice.

Read the arXiv preprint | Read my Twitter-poster summary of the results! | Watch my talk at CAP 2021!

Strong-coupling corrections to hard domain walls in superfluid 3He-B

Physical Review B 104, 094520 – Published 22 September 2021

M.J. Rudd, P. Senarath Yapa, A.J. Shook, J. Maciejko and J.P. Davis

Domain walls in superfluid 3He-B have gained renewed interest in light of experimental progress on confining helium in nanofabricated geometries. Here, we study the effect of strong-coupling corrections on domain wall width and interfacial tension by determining self-consistent solutions to spatially-dependent Ginzburg-Landau equations. We find that the formation of domain walls is generally energetically favored in strong coupling over weak coupling. Calculations were performed over a wide range of temperatures and pressures, showing decreasing interface energy with increasing temperature and pressure. This has implications for the observability of such domain walls in 3He-B, which are of both fundamental interest and form the basis for spatially-modulated pair-density wave states, when stabilized by strong confinement.

Read the PRB | Read the arXiv preprint | Read my Twitter summary of the paper!

Stabilized Pair Density Wave via Nanoscale Confinement of Superfluid 3-He

Physical Review Letters 124, 015301 – Published 3 January 2020

A.J. Shook, V. Vadakkumbatt, P. Senarath Yapa, C. Doolin, R. Boyack, P.H. Kim, G.G. Popowich, F. Souris, H. Christani, J. Maciejko, and J.P. Davis

Superfluid 3-He under nanoscale confinement has generated significant interest due to the rich spectrum of phases with complex order parameters that may be stabilized. Experiments have uncovered a variety of interesting phenomena, but a complete picture of superfluid 3-He under confinement has remained elusive. Here, we present phase diagrams of superfluid 3-He under varying degrees of uniaxial confinement, over a wide range of pressures, which elucidate the progressive stability of both the A phase, as well as a growing region of stable pair density wave state.

Read the PRL | Read the arXiv preprint | Read the Phys.org news release

Impact of Nonlocal Electrodynamics on the Flux Noise and Inductance of Superconducting Wires

Physical Review Applied 11, 024041 – Published 15 February 2019

P. Senarath Yapa, Tyler Makaro, and Rogério de Sousa

We present exact numerical calculations of the supercurrent density, inductance, and impurity-induced flux noise of cylindrical superconducting wires in the nonlocal Pippard regime, which occurs when the Pippard coherence length is greater than the London penetration depth. In this regime, the supercurrent density displays a peak away from the surface and changes sign inside the superconductor, signaling a breakdown of the usual approximation of local London electrodynamics with a renormalized penetration depth. Our calculations show that the internal inductance and the bulk flux noise power are enhanced in nonlocal superconductors. In contrast, the kinetic inductance is reduced and the surface flux noise remains the same. As a result, impurity spins in the bulk may dominate the flux noise in superconducting qubits in the Pippard regime, such as the ones using aluminum superconductors with a large electron mean free path.

Read the PRApplied | Read the arXiv preprint |
Read the Advances in Engineering article

Education.

  • 2018-Present

    University of Alberta, Edmonton AB, Canada

    PhD Student in Condensed Matter Theory, Department of Physics

    Thesis: Exotic Phases of Confined Superfluid 3-He Co-supervised by Prof. Joseph Maciejko and Prof. Frank Marsiglio

  • 2015-2018

    University of Victoria, Victoria BC, Canada

    MSc. in Condensed Matter Theory, Department of Physics

    Thesis: Non-Local Electrodynamics of Superconducting Wires: Implications for Flux Noise and Inductance supervised by Prof. Rogério de Sousa

  • 2010-2015

    Carleton University, Ottawa ON, Canada

    Honours BSc. in Theoretical Physics and Minor in Mathematics, Department of Physics

    Honours Thesis: Supersymmetry Phenomenology Supervised by Prof. Thomas Gregoire

Selected Presentations.

Contact.

pramodhsy(at)ualberta(dot)ca
  • 3-145,
  • Centennial Center for Interdisciplinary Science (CCIS),
  • Department of Physics,
  • University of Alberta
  • Edmonton, AB
  • Canada, T6H 2T5

The University of Alberta respectfully acknowledges that we are located on Treaty 6 territory, a traditional gathering place for diverse Indigenous peoples including the Cree, Blackfoot, Métis, Nakota Sioux, Iroquois, Dene, Ojibway/ Saulteaux/Anishinaabe, Inuit, and many others whose histories, languages, and cultures continue to influence our vibrant community.