Dr. Pramodh Senarath Yapa

Mixed-symmetry superconductivity and the energy gap

Physica C: Superconductivity and its Applications 633, 1354719 – Published 15 June 2025

P. Senarath Yapa, X. Guo, J. Maciejko and F. Marsiglio

The symmetry of the superconducting order parameter, or simply the ``gap'', provides certain constraints on the actual mechanism that gives rise to pairing and ultimately to superconductivity. In this work we show how superconducting phases with mixed singlet-triplet symmetries can arise below Tc for a generic tight-binding model. We first examine the 1D case to better illustrate the prevalence of symmetry-breaking transitions below Tc, and then the more realistic 2D case. In both cases we illustrate the implication for spectroscopic investigations of the energy gap by calculating the density of states for different temperatures below Tc. We find that the structure of the density of states near Tc can vary dramatically from its form near T=0. A complete picture of the superconducting symmetry can only be attained if measurements are made over the entire temperature range.

Read the Physica C | Read the arXiv preprint

Supersonic shear waves in dipolar supersolids

ArXiv preprint (arXiv:2410.16060) – Posted 22 October 2024

P. Senarath Yapa, and T. Bland

Dipolar supersolids--quantum states which are simultaneously superfluid and solid--have had their superfluid nature rigorously tested, while its solid nature remains uncharted. Arguably, the defining characteristic of a solid is the existence of elastic shear waves. In this work, we investigate transverse wave packet propagation in dipolar supersolids with triangular and honeycomb structure. Remarkably, the honeycomb supersolid displays anomalous dispersion, supporting waves traveling faster than the transverse speed of sound: a supersonic shear wave. For both supersolid phases, we calculate the shear modulus, a key parameter that quantifies the material's rigidity. Our findings are pertinent to current experimental efforts scrutinizing the fundamental properties of supersolids.

Read the arXiv preprint

Triangular Pair-Density Wave in Confined Superfluid Helium-3

Physical Review Letters 128, 015301 – Published 7 January 2022

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 PRL | Read the arXiv preprint | Read my Twitter summary! | Watch my talk at APS March 2022!

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!

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

2023-Now
Universität Innsbruck, Innsbruck, Tyrol, Austria

Postdoctoral Researcher, Institut für Experimentalphysik

Focus: Solid properties of the Dipolar Supersolid

Co-supervised by Dr. Thomas Bland and Prof. Francesca Ferlaino
2018-2024
University of Alberta, Edmonton AB, Canada

PhD in Condensed Matter Theory, Department of Physics

Thesis: Unconventional Cooper Pairing and Confinement

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

APS March 2022: Triangular Pair-Density Wave in Confined Superfluid Helium-3

A 10-minute talk about my newest paper on the superfluid cystal phase of Helium-3 given at the American Physical Society (APS) March Meeting 2022.
VPC2020: Superfluid Helium Introduction

A 10-minute talk about my research on superfluid Helium-3 given at the TRU Virtual Physics Conference 2020. VPC2020 was a Virtual Conference that I co-organized shortly after the COVID19 shutdown (thus the funny virtual avatars), and was aimed at replacing the opportunities lost due to the cancellation of many conferences. This talk was aimed at an upper-year undergraduate level.
QFI2020 Superfluid Helium-3 Within The Confines

A 50-minute invited seminar about the physics of superfluid Helium-3 when confined to a thin slab, given at the Quantum Fluids in Isolation Seminar Series. This talk is aimed at active researchers within the Quantum Fluids community, but the first half should be accesible for most.

Science Telephone Podcast

The Science Telephone Podcast has a new take on the old game of 'Telephone'; what happens when you pass jargon-y scientific research through the minds of 3 comedians in turn? I was delighted to be the token scientist on this fun podcast, where my research into superfluids was somehow converted into a tale about the movie 'The Matrix'. Give 'er a listen!
Interview on the Nerdin' About Podcast

I was invited onto the Nerdin' About Podcast to talk about Quantum stuff, superfluids and SciComm! Thank you to Dr. Kaylee Byers and Michael Unger for having me on!
Interview about SciComm by the DSC at the University of Alberta

Hanne Pearce at the Digital Scholarship Centre at UAlberta interviewed me about my approach to Science Communcation! Listen in if you want to hear about why I think #SciComm is important, the ways to harnesss your inspiration to make creative science communcation pieces and obstacles that you may encounter while doing it!