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1. Josephson Detection of Time Reversal Symmetry Breaking s +/- is Superconductivity in SnTe Nanowires

   Trimble, C.; Wei, M. T.; Kalantre, S. S.; Yuan, N. F.; Liu, P.; Cha, J. J.; Fu, L.; Williams, J. R. (January 2019, ArXiv.org)

   Exotic superconductivity, such as high TC, topological, and heavy-fermion superconductors, often rely on phase sensitive measurements to determine the underlying pairing. Here we investigate the proximity-induced superconductivity in nanowires of SnTe, where a s±is′ superconducting state is produced that lacks the time-reversal and valley-exchange symmetry of the parent SnTe. A systematic breakdown of three conventional characteristics of Josephson junctions -- the DC Josephson effect, the AC Josephson effect, and the magnetic diffraction pattern -- fabricated from SnTe nanowire weak links elucidates this novel superconducting state. Further, the AC Josephson effect reveals evidence of a Majorana bound state, tuned by a perpendicular magnetic field. This work represents the definitive phase-sensitive measurement of novel s±is′ superconductivity, providing a new route to the investigation of fractional vortices, topological superconductivity, topological phase transitions, and new types of Josephson-based devices. 

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2. Superfluid helium-4 in porous structures of neon-nitrogen nanoclusters as a target for low-mass dark matter detector

   https://doi.org/10.3389/fdest.2025.1585561  

   Boltnev, R E; Khmelenko, V V (July 2025, Frontiers in Detector Science and Technology)

   Borghesani, Armando F (Ed.)

   A new concept of three-phase projection chamber filled with a collection of neon-nitrogen nanoclusters immersed in superfluid helium-4 is proposed for detection light dark matter particles with low masses (0.1–10 Gev/c²). Such a time projection chamber includes a drift region within aerogel-like structure formed by neon-nitrogen nanoclusters filled by superfluid helium and a gas phase camera where electroluminescence takes place. The proposed concept combines the promising properties of liquid helium as a target material for direct detection of light dark matter particles such as high quenching factor, substantial scintillation light, high radiopurity, and high impedance to external vibration noise with the new ones determined by the properties of solid neon and nitrogen. The presence of highly porous impurity structure will enhance the primary scintillation signal (S1) due to light emission stimulated by interactions of metastable He₂(a³Σ_u) molecules and He⁺ions with impurity nanoclusters. The signal of electrons produced by the recoil event (S2) and drifting in external electric field will get additional input due to energy stored in nitrogen atoms stabilized on the nanoclusters’ surface. 

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3. Nature of the spin resonance mode in CeCoIn5

   https://doi.org/10.1038/s42005-020-0365-8  

   Song, Yu; Wang, Weiyi; S. Van Dyke, John; Pouse, Naveen; Ran, Sheng; Yazici, Duygu; Schneidewind, A.; Čermák, Petr; Qiu, Y.; Maple, M. B.; et al (May 2020, Communications Physics)

   Abstract Spin-fluctuation-mediated unconventional superconductivity can emerge at the border of magnetism, featuring a superconducting order parameter that changes sign in momentum space. Detection of such a sign-change is experimentally challenging, since most probes are not phase-sensitive. The observation of a spin resonance mode (SRM) from inelastic neutron scattering is often seen as strong phase-sensitive evidence for a sign-changing superconducting order parameter, by assuming the SRM is a spin-excitonic bound state. Here we show that for the heavy fermion superconductor CeCoIn₅, its SRM defies expectations for a spin-excitonic bound state, and is not a manifestation of sign-changing superconductivity. Instead, the SRM in CeCoIn₅likely arises from a reduction of damping to a magnon-like mode in the superconducting state, due to its proximity to magnetic quantum criticality. Our findings emphasize the need for more stringent tests of whether SRMs are spin-excitonic, when using their presence to evidence sign-changing superconductivity. 

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4. Dual-phase superconductivity in high-pressure high-temperature synthesized TaNbZrHfTi

   https://doi.org/10.1063/5.0214797  

   Sereika, Raimundas; Iwan, Seth; Baker, Paul_A; Bi, Wenli; Vohra, Yogesh_K (June 2024, AIP Advances)

   We report on a novel TaNbZrHfTi-based high entropy alloy (HEA) which demonstrates distinctive dual-phase superconductivity. The HEA was synthesized under high pressures and high temperatures starting from a ball milled mixture of elemental metals in a large-volume Paris–Edinburgh cell with P ≈ 6 GPa and T = 2300 K. The synthesized HEA is a phase mixture of BCC (NbTa)0.45(ZrHfTi)0.55 with Tc1 = 6 K and FCC (NbTa)0.04(ZrHfTi)0.96 with Tc2 = 3.75 K. The measured magnetic field parameters for the HEA are lower critical field, Hc1(0) = 31 mT, and a relatively high upper critical field, Hc2(0) = 4.92 T. This dual-phase system is further characterized by the presence of a second magnetization peak, or the fishtail effect, observed in the virgin magnetization curves. This phenomenon, which does not distort the field-dependent magnetization hysteresis loops, suggests intricate pinning mechanisms that could be potentially tuned for optimized performance. The manifestation of these unique features in HEA superconductivity reinforces phase-dependent superconductivity and opens new avenues in the exploration of novel superconducting materials. 

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5. Unconventional superconducting phase diagram of monolayer ${\mathrm{WTe}}_2$

   https://doi.org/10.1103/PhysRevResearch.7.013224  

   Song, Tiancheng; Jia, Yanyu; Yu, Guo; Tang, Yue; Uzan, Ayelet J; Zheng, Zhaoyi Joy; Guan, Haosen; Onyszczak, Michael; Singha, Ratnadwip; Gui, Xin; et al (February 2025, Physical Review Research)

   The existence of a quantum critical point (QCP) and fluctuations around it are believed to be important for understanding the phase diagram in unconventional superconductors such as cuprates, iron pnictides, and heavy fermion superconductors. However, the QCP is usually buried deep within the superconducting dome and is difficult to investigate. The connection between quantum critical fluctuations and superconductivity remains an outstanding problem in condensed matter. Here combining both electrical transport and Nernst experiments, we explicitly demonstrate the onset of superconductivity at an unconventional QCP in gate-tuned monolayer tungsten ditelluride $\left({\mathrm{WTe}}_2\right)$, with features incompatible with the conventional Bardeen-Cooper-Schrieffer scenario. The results lead to a superconducting phase diagram that is distinguished from other known superconductors. Two distinct gate-tuned quantum phase transitions are observed at the ends of the superconducting dome. We find that quantum fluctuations around the QCP of the underdoped regime are essential for understanding how the monolayer superconductivity is established. The unconventional phase diagram we report here illustrates a previously unknown relation between superconductivity and QCP. Published by the American Physical Society2025 

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