Topological Mesoscopic Superfluidity

Superfluid 3He, supporting multiple phases with p-wave order parameter, provides a unique testbed for the study of topological superconductivity, and the surface and edge excitations which emerge through bulk-surface correspondence.

Topological phases of superfluid 3He

We have pioneered the approach of engineering the order parameter of superfluid 3He by confinement in a nanofabricated cavity of height comparable to the superfluid coherence length. The coherence length can be varied by the liquid pressure, while specular surface scattering of quasiparticles at surfaces can be achieved by plating with a superfluid 4He film.  A powerful tool is the ability to determine the order parameter of this neutral unconventional superfluid by NMR. We have developed SQUID NMR spectrometers of high sensitivity as a non-invasive probe.

In this way the relative stability under confinement of the chiral A-phase and time reversal invariant B-phase has been determined. Furthermore under such conditions new phases emerge; quasi-2D chiral A-phase and pair density wave states have already been identified. Stabilizing the polar phase (in the absence of disorder) and superfluid 3He in the fully 2D limit are on the horizon.

Surface, edge and interface states

Superfluid 3He supports a diverse range of topological states, and provides a model for topological superconductivity, yet to be firmly identified in any other condensed matter system. Furthermore the order parameter “sculpture” by symmetry-breaking confining geometries opens the door to engineered 3He hybrid nanostructures. Interfaces between two 3He quantum material phases can be stabilized by a step in cavity height. Superfluid meta-materials may also be fabricated by structured nanoscale confinement.

At a specular scattering (mirror-like) surface, superfluid 3He-B hosts mid-gap excitations related to Majorana fermions. The chiral superfluid 3He-A supports edge modes. We are developing NMR and transport methods to characterise these states.

Cosmological analogues

Superfluid 3He also provides a model system for laboratory-based insights into phase transitions in the early universe, relevant to future searches for gravitational wave signatures in space based detectors such as LISA (Laser Interferometer Space Antenna). The transition between the A and B phases, of distinct symmetry, in superfluid 3He is first order. Usually this transition is triggered by extrinsic factors, either internal in the sample chamber, or ionising radiation (cosmic rays or radiogenic background from cryostat materials. We are studying this phase transition in small isolated volumes of superfluid 3He, created by nanofabrication techniques, where NMR is used as a non-invasive probe, where the extrinsic factors can be essentially eliminated.

Dark Matter detection

The application of superfluid 3He as a detector of theoretically motivated dark matter candidates in the mass range 0.1 to 10 GeV, inaccessible to previous searches, is under development, and part of the QUEST-DMC project.

References

  1. Fragility of surface states in topological superfluid 3He J. Heikkinen, A. Casey, L. V. Levitin, X. Rojas, A. Vorontsov, P. Sharma, N. Zhelev, J. M. Parpia and J. Saunders Nature Communication, 1574 (2021)
  2. Comment on “Stabilized pair density wave in nanoscale confinement of superfluid 3He”. L. Levitin, X. Rojas, P. Heikkinen, A. Casey, J. Parpia, J. Saunders Phys. Rev. Lett. 125, 059601 (2020)
  3. Realizing quantum materials with Helium: Helium films at ultralow temperatures, from strongly correlated atomically layered films to topological superfluidity, J. Saunders in Topological Phase Transitions and New Developments, p. 165-196 (2019). Ed. Lars Brink, Mike Gunn, Jorge V Jose, John Michael Kosterlitz, Kok Phoo Phua (World Scientific). http://arxiv.org/abs/1910.01058
  4. Evidence for a Spatially Modulated Superfluid Phase of 3He under Confinement Lev V. Levitin, Ben Yager, Laura Sumner, Brian Cowan, Andrew J. Casey, John Saunders, Nikolay Zhelev, Robert G. Bennett, and Jeevak M. Parpia Phys. Rev. Lett. 122, 085301 (2019) PRL 122,08531 (2019) [Selected for Viewpoint: A Polka-Dot Pattern Emerges in Superfluid Helium]
  5. Fabrication of microfluidic cavities using Si-to-glass anodic bonding N Zhelev, TS Abhilash, RG Bennett, EN Smith, B Ilic, JM Parpia, LV Levitin, X Rojas, A Casey, J Saunders Review of Scientific Instruments 89, 073902 (2018) RSI 89 073902 (2018)
  6. Phase Diagram of the Topological Superfluid 3He Confined in a Nanoscale Slab Geometry. L. Levitin, R. Bennett, A. Casey, B. Cowan, J. Saunders, D. Drung, T. Schurig, J. Parpia Science 340, 841 (2013)
  7. Surface Induced Order Parameter Distortion in Superfluid 3He-B Measured by Non-Linear NMR, L. Levitin, R. Bennett, E. Surovtsev, J. Parpia, B. Cowan, A. Casey, J. Saunders. Phys. Rev. Lett. 111, 235304 (2013)
  8. Levitin, R. Bennett, A. Casey, B. Cowan, J. Saunders, D. Drung, Th. Schurig, J. Parpia, B. Ilic, N. Zhelev: Study of superfluid 3He under nanoscale confinement: A new approach to the investigation of superfluid 3He films. J. Low Temp. Phys. 175, 667-680 (2014) JLTP 175 667 (2014).
  9. A nuclear magnetic resonance spectrometer for operation around 1 MHz with a sub-10 mK noise temperature, based on a two stage DC SQUID sensor. LV Levitin, RG Bennett, A Casey, BP Cowan, CP Lusher, J Saunders, D Drung, Th Schürig. Applied Physics Letters 91, 262507 (2007) APL 91 262507 (2007)

Collaborative research at Cornell:

  1. Supercooling of the A phase of 3 Y. Tian, D. Lotnyk, A. Eyal, K. Zhang, N. Zhelev, T. Abilash, A. Chavez, E. Smith, M. Hindmarsh, J. Saunders, E. Mueller and J. Parpia. Nature Communications, 14, 148 (2023)
  2. Path dependent supercooling of the 3He superfluid A-B transition. Dmytro Lotnyk, Anna Eyal, Nikolay Zhelev, Abhilash Sebastian, Yefan Tian, Aldo Chavez, Eric Smith, John Saunders, Erich Mueller, Jeevak Parpia, Phys. Rev. Lett. 126, 215301 (2021)
  3. Thermal transport of helium-3 in a strongly confining channel.  Lotnyk, A, Eyal, N. Zhelev, T. Abhilash, E. Smith, M. Terilli, J. Wilson, E. Mueller, D. Einzel, J. Saunders, J. Parpia. Nature Communication, 4843 (2020).