Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session K44: 2D Materials: SuperconductorsFocus
|
Hide Abstracts |
Sponsoring Units: DMP Chair: Yang Liu; Salvador Barraza-Lopez, University of Arkansas Room: Room 316 |
Tuesday, March 7, 2023 3:00PM - 3:36PM |
K44.00001: Superconductivity and Ferroelectricity Few-Layer Td-MoTe2 Invited Speaker: Daniel Rhodes I will discuss how the influence of an electrostatic gate allows us to identify a unique superconducting state in bilayer Td-MoTe2 and its profound influence even when no change in the chemical potential is made. Our results indicate that superconductivity in bilayer Td-MoTe2 can be completely quenched by an electrostatic gate, and that the superconducting behavior is connected to Fermi surface nesting between electron and hole pockets. In addition, due to the noncentrosymmetric crystal structure of bilayer Td-MoTe2 ferroelectric behavior, as a result of interlayer sliding, is established. This behavior, concomitant with superconductivity, allows for the first investigations of how internal polarization might conflict with or enhance superconductivity in the two-dimensional limit. |
Tuesday, March 7, 2023 3:36PM - 3:48PM |
K44.00002: Understanding pseudogaps in high Tc materials Eric J Heller, Alhun Aydin, Donghwan Kim, Joonas Keski-Rahkonen, Zunqi Li, Hongkun Chen, Anton Graf We begin with the observation that acoustic bands and carrier bands cross on an interesting 1D manifold for 2D materials. The reason is that the acoustic band rises linearly from the Gamma point k=0, while the carrier band rises quadratically. The carrier band catches up to the phonon dispersion at higher k. The existence of this intersection is apparently missing in the literature. It is also buried deep in the Fermi sea for normal metals and unimportant. However this crossing becomes important for the emerging carrier bands in low doped cuprates. At every point on the intersection manifold, both phonon and carrier have the same frequency (energy) and the same wavelength, setting up a strong resonance. This resonance disrupts the carrier bands wherever this 1D track crosses them, causing gaps. Wherever the "gap track", as we call it, crosses the Fermi surface, probes like ARPES will find the carrier density simply missing - a gap. The rest of the Fermi surface not crossed by the gap track survives. Thus the Fermi arcs are naturally surviving segments of the usual Fermi surface. The spectral intensitiy is conserved, but cast far and wide, and the gap gives the appearance of being uncompensated. This talk will present strong evidence that these gap tracks agree with and explain the gap patterns seen in photoemission and ARPES. The phonon-carrier intersection gives rise to an avoided crossing and a new quasiparticle which we call a "vibron". The whole scenario is in perfect analogy to polariton physics, with the role of photon being played by the phonon. The mechanism we find also strongly suggests a path to incommensurate charge density waves. |
Tuesday, March 7, 2023 3:48PM - 4:00PM |
K44.00003: Theoretical determination of the effect of a screening gate on the superconductivity in twisted bilayer graphene Shaffique Adam, Giovanni Vignale, Liangtao Peng, Indra Yudhistira Motivated by recent experiments in twisted bilayer graphene with an additional screening layer [Stepanov et al. Nature 583 375 (2020); Saito et al. Nature Physics 926 (2020); Science 371 1261 (2021)], we study theoretically the effect of a screening layer on the superconducting transition temperature. It is widely believed that a plasmonic origin, but not a phononic origin of superconductivity will be strongly suppressed by a screening gate. We find that the situation is more complicated: For a plasmonic pairing mechanism [1], we find a metallic screening gate has only a weak effect on superconducting transition for distances larger than 10 nm. At short screening distances, we find that the transition temperature has a non-monotonic dependence on the screening layer carrier density which provides a clear experimental signature to test for a plasmonic origin of the observed superconductivity. |
Tuesday, March 7, 2023 4:00PM - 4:12PM |
K44.00004: Effect of electron doping in AV3Sb5 kagome superconductor system Andrea N Capa Salinas The kagome structure embodies a most promising playground for the realization of emergent phenomena. The recently discovered kagome metals of the family AV3Sb5 (A=K,Rb,Cs) have renewed an interest into the exciting dynamics of the kagome structure, for they exhibit electronic and structural instabilities like charge fractionalization, superconductivity, and charge density waves. Our particular focus is to understand the apparent competition between the latter two phenomena. Namely, we studied the effect of electron doping in powders and single crystal versions of our system and observed a suppression of the charge density wave transition temperature and superconducting transition temperature with small electron doping concentrations. These results, complementary with hole doping analysis of the system, lay the foundation for the exploration of the complex interplay between charge density wave and superconducting states in this material. |
Tuesday, March 7, 2023 4:12PM - 4:24PM |
K44.00005: Examining the role of spin-orbit coupling in superconducting Bernal bilayer graphene Chennan He, Aravind Devarakonda, Joshua Swann, Song Liu, Kenji Watanabe, Takashi Taniguchi, James C Hone, Cory R Dean Ultra-clean, moiré-less Bernal bilayer graphene (BLG) exhibits a variety of emergent ground states driven by strong electron-electron interactions [1–3]. The observation of spin-polarized superconductivity is of particular interest. Recent work has shown that the superconducting transition temperature Tc in BLG is an order-of-magnitude higher when spin-orbit coupling is induced by proximity to the transition metal dichalcogenide H-WSe2 [4]. We fabricate WSe2-BLG heterostructures to explore the interplay between twist angle and pressure and their effects on electronic properties [5]. |
Tuesday, March 7, 2023 4:24PM - 4:36PM |
K44.00006: Diamagnetic response and phase stiffness for interacting isolated narrow bands Dan Mao, Debanjan Chowdhury Superconductivity in electronic systems, where the non-interacting bandwidth for a set of isolated bands is small compared to the scale of the interactions, is a non-perturbative problem. Here we present a theoretical framework for computing the electromagnetic response in the limit of zero frequency and vanishing wavenumber for the interacting problem, which controls the superconducting phase stiffness, without resorting to any mean-field approximation. Importantly, the contribution to the phase stiffness arises from (i) ``integrating-out" the remote bands that couple to the microscopic current operator, and (ii) the density-density interactions projected on to the isolated bands. We also obtain the electromagnetic response directly in the limit of an infinite gap to the remote bands, using the appropriate ``projected" gauge-transformations. These results can be used to obtain a conservative upper bound on the phase stiffness, and relatedly the superconducting transition temperature, with a few assumptions. We apply this formalism to a host of topologically (non-)trivial ``flat-band" systems, including twisted bilayer graphene. |
Tuesday, March 7, 2023 4:36PM - 4:48PM |
K44.00007: Spin-valley polarization in NbSe2 at van der Waals interface Hideki Matsuoka, Tetsuro Habe, Yoshihiro Iwasa, Mikito Koshino, Masaki Nakano Van der Waals materials attract growing interest as a site for the emergence of various two-dimensional (2D) properties, including luminescence properties, 2D superconductivity, 2D magnetism, and topological quantum conduction. One of the essential factors that have supported the development of vdW materials research is the symmetry breaking of the crystal structure unique to vdW materials. Among them, transition metal dichalcogenides (TMDs) with H-type polymorphism have a unique Zeeman-type spin-orbit interaction (SOI), which reflects the broken spatial inversion symmetry in the monolayer limit. A variety of novel properties coupled to the Zeeman-type SOI have been reported, such as valley-polarized luminescence and transport properties in semiconductor TMDs such as MoS2 and WSe2, and unconventional superconductivity in metal TMDs such as NbSe2 and TaS2. Here, we have focused on the effect of Zeeman-type SOI on magnetic properties and have reported the ferromagnetic modulation by Zeeman-type SOI in the heterostructure of NbSe2 with Zeeman-type SOI and ferromagnetic vanadium selenide1. |
Tuesday, March 7, 2023 4:48PM - 5:00PM |
K44.00008: Superconductivity in cleavable, van der Waals layered crystals Michael A McGuire, Jiaqiang Yan, Robert G Moore, Satoshi Okamoto, Andrew F May, Xiaoping Wang, Matthew Brahlek, Yun-Yi Pai, Heda Zhang, Clement Girod, Sean Thomas, Filip Ronning I will present results of our recent studies of superconductivity in pseudo-2D cleavable compounds, specifically in PtTe and in the GeAs2Te4 family. PtTe is the only reported non-halide adopting the layered ZrCl structure type and contains double layers of Pt between Te layers with the Te-Pt-Pt-Te slabs separated by a van der Waals gap. Electronic structure calculations indicate PtTe is a topological semimetal. The platelike crystals grown from a Pt flux show type-II superconductivity with Tc = 0.57 K. The well-known GeAs2Te4 structure type is adopted by the intrinsic antiferromagnetic topological insulator MnBi2Te4 and many other candidate topological materials. In this family we induce superconductivity in SnBi2Te4 by alloying and find Tc up to 1.85 K. The presence of both superconductivity and topological surface states may present an opportunity to realize topological superconductivity through an intrinsic proximity effect in this material. |
Tuesday, March 7, 2023 5:00PM - 5:12PM |
K44.00009: Probing the electronic structure of chemically-induced van der Waals heterostructures in VxTaS2 Wojciech R Pudelko, Huanlong Liu, Karin von Arx, Qisi Wang, Julia Küspert, Eduardo Bonini-Guedes, Hang Li, Francesco francesco.petocchi, Philipp Werner, Andreas J Schilling, Johan Chang, Nicholas C Plumb Layered transition metal dichalcogenides exhibit numerous exotic electronic phases, and their heterostructures are seen as promising platforms for quantum materials investigations and technologies. We found that dilute intercalation of vanadium into the 2H structural phase of TaS2 (VxTaS2) leads to intriguing changes in the electronic properties, including nearly a factor-of-3 enhancement of optimal superconducting Tc near x = 0.05.Using ARPES, we observe significant changes in the electronic structure with increasing x: The system evolves from the pure 2H band structure known for its charge density wave (CDW) and superconducting phases to a pure 1T electronic structure characterized by CDW and Mott interactions, as well as possible quantum spin glass behavior. Along the way, at intermediate x near the optimal Tc, the in-plane electronic structure is comprised of both 2H- and 1T-like bands. The weak out-of-plane electronic dispersion shows a distinct change in periodicity, indicating that these polymorphs are indeed stacked, rather than arranged side-by-side. By exploiting V intercalation as a means to assemble 2H/1T van der Waals heterostructures, we are granted an exceptionally clear spectroscopic window into each layer type, as well as the interplay between their electronic phases. |
Tuesday, March 7, 2023 5:12PM - 5:24PM |
K44.00010: Overdamped Phase Diffusion in hBN Encapsulated Graphene Josephson Junctions Amis Sharma, Jiayin Tang, Ethan G Arnault, Ming Tso Wei, Andrew M Seredinski, Yash Mehta, Kenji Watanabe, Takashi Taniguchi, Francois Amet, Ivan V Borzenets Hexagonal Boron-Nitride encapsulated Graphene based Josephson junctions (SGS) are in an active stage for studying superconducting phenomena and applications. As such, it is necessary to study how interaction with the environment affects junction behavior. This work characterizes damping behavior by experimentally investigating the phase diffusion mechanism. At non-zero temperature, the SGS can be briefly excited above its superconducting state by thermal noise, the state is quickly recovered, albeit with a net phase shift. The phase shift results in a measurable voltage, even at zero bias current. Josephson junctions can be underdamped or overdamped regime as dictated by the interaction with its environment. Vast majority of previous experimental studies have shown SGS devices to be slightly-to moderately under damped[1]. Here, we conclusively demonstrate overdamped behavior in a SGS, characterized via phase diffusion[2]. Moreover, we present a framework in order to design future underdamped devices. Our results have relevance for SGS-based quantum information devices. |
Tuesday, March 7, 2023 5:24PM - 5:36PM |
K44.00011: Superconductivity in Twisted Double Bilayer Graphene Stabilized by WSe2 Ruiheng Su, Manabendra Kuiri, Kenji Watanabe, Takashi Taniguchi, Joshua Folk Twisted double bilayer graphene (TDBG) provides a fascinating platform to study correlated electron physics, where the bandwidth and band topology can be tuned by gate voltages. Although correlated insulating states, anomalous hall effect, and signatures of non-trivial band topology have been realized, superconductivity has not, despite its appearance in other graphene-based van der Waals heterostructures. Here, we report on the observation of superconductivity in TDBG proximitized with semiconducting WSe2, based on two WSe2/TDBG samples with twist angles of 1.24 and 1.37 degrees. Superconductivity emerged in the first moiré valence band for the 1.24 degree sample, and in the conduction band for the 1.37 degree sample, both with a small critical temperature of ~100 mK. Superconductivity was confirmed by non-linear current-voltage characteristics, and suppression of critical current with perpendicular magnetic field showing phase coherent Fraunhofer-like patterns. In both cases, low-field Hall measurements reveal that superconductivity emerges from a spin-valley degenerate metal, but close to a van Hove singularity and adjacent to a region susceptible to interaction-induced spin polarization. These results highlight the correlation between a high density of states and the emergence of superconductivity in TDBG while indicating a possible role for spin fluctuations in the pairing. |
Tuesday, March 7, 2023 5:36PM - 5:48PM |
K44.00012: Fabricating quantum point contact in monolayer WTe2 Yue Tang, Yanyu Jia, Tiancheng Song, Pengjie Wang, Guo Yu, Ratnadwip Singha, Xin Gui, Kenji Watanabe, Takashi Taniguchi, Robert Cava, Leslie M Schoop, Sanfeng Wu Quantum point contact (QPC), which explores one-dimensional electronic transport channel, has attracted a lot of interests for engineering quantum devices and exploring low-dimensional quantum physics. Exploring the effects of QPC in systems that combine superconductivity and topology is promising to reveal new phenomena in previously unexplored regime. In this talk, I will present our effort in creating QPC device in a topologically non-trivial 2D crystal, the monolayer tungsten ditelluride (WTe2), which has been established as a quantum spin hall insulator and a gate-induced superconductor in a single material. I will describe our fabrication process of a QPC device in WTe2 monolayer and the experimental data that paves the way for the further exploration. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700