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Poniatowski, Nicholas R.

Publications and source records attributed to Poniatowski, Nicholas R..

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Stabilizing Fluctuating Spin-Triplet Superconductivity in Graphene via Induced Spin-Orbit Coupling

A recent experiment showed that a proximity-induced Ising spin-orbit coupling enhances the spin-triplet superconductivity in Bernal bilayer graphene. Here, in this work, we show that, due to the nearly perfect spin rotation symmetry of graphene, the fluctuations of the spin orientation of the triplet order parameter suppress the superconducting transition to nearly zero temperature. Our analysis shows that both an Ising spin-orbit coupling and an in-plane magnetic field can eliminate these low-lying fluctuations and can greatly enhance the transition temperature, consistent with the recent experiment. Our model also suggests the possible existence of a phase at small anisotropy and magnetic field which exhibits quasilong-range ordered spin-singlet charge 4⁢e superconductivity, even while the triplet 2⁢e superconducting order only exhibits short-ranged correlations. Finally, we discuss relevant experimental signatures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Surface Cooper-Pair Spin Waves in Triplet Superconductors

Here, we study the electrodynamics of spin triplet superconductors including dipolar interactions, which give rise to an interplay between the collective spin dynamics of the condensate and orbital Meissner screening currents. Within this theory, we identify a class of spin waves that originate from the coupled dynamics of the spin-symmetry breaking triplet order parameter and the electromagnetic field. In particular, we study magnetostatic spin wave modes that are localized to the sample surface. We show that these surface modes can be excited and detected using experimental techniques such as microwave spin wave resonance spectroscopy or nitrogen-vacancy magnetometry, and propose that the detection of these modes offers a means for the identification of spin triplet superconductivity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Proximity-induced collective modes in an unconventional superconductor heterostructure

Unconventional superconductors have been long sought for their potential applications in quantum technologies and devices. A key challenge impeding this effort is the difficulty associated with probing and characterizing candidate materials and establishing their order parameter. Here we present a platform that allows one to spectroscopically probe unconventional superconductivity in thin-layer materials via the proximity effect. Here we show that inducing an s-wave gap in a sample with an intrinsic d-wave instability leads to the formation of bound states of quasiparticle pairs, which manifest as a collective mode in the d-wave channel. This finding provides a way to study the underlying pairing interactions vicariously through the collective mode spectrum of the system. Upon further cooling of the system we observe that this mode softens considerably and may even condense, signaling the onset of time-reversal symmetry-breaking superconductivity. Therefore, our proposal also allows for the creation and study of these elusive unconventional states.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Spectroscopic signatures of time-reversal symmetry breaking superconductivity

The collective mode spectrum of a symmetry-breaking state, such as a superconductor, provides crucial insight into the nature of the order parameter. In this work, we study two collective modes which are unique to unconventional superconductors that spontaneously break time reversal symmetry. We show that these modes are coherent and underdamped for a wide variety of time-reversal symmetry breaking superconducting states. By further demonstrating that these modes can be detected using a number of existing experimental techniques, we propose that our work can be leveraged as a form of “collective mode spectroscopy” that drastically expands the number of experimental probes capable of detecting time-reversal symmetry breaking in unconventional superconductors.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Hidden strange metallic state in underdoped electron-doped cuprates

The low-temperature linear-in-T resistivity of “strange metals,” such as the metallic state of the cuprate high-temperature superconductors, has long been thought to be associated with a quantum critical point. However, recent transport studies of the cuprates have found this behavior persists over a finite range of overdoping. Here, in this work, we report magnetoresistance and Hall effect results for electron-doped films of the cuprate superconductor La 2-x ⁢ Ce x CuO 4 (LCCO) for temperatures from 0.7 to 45 K and magnetic fields up to 65 T. For x = 0.12 and 0.13, just below the Fermi surface reconstruction (FSR) at x = 0.14, the normal state in-plane resistivity exhibits a well-known upturn at low temperature. Our new results show that this resistivity upturn is eliminated at high magnetic field and the resistivity becomes linear-in-temperature from ~40 K down to 0.7 K. The magnitude of the linear coefficient scales with Tc and doping, as found previously for dopings above the FSR. This striking observation suggests that the strange metal is not confined to a single “critical point” in the phase diagram, but rather is a robust universal feature of the metallic ground state of the cuprates.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗