Figure - available from: Nature Physics
This content is subject to copyright. Terms and conditions apply.
Two-dimensional superconductivity in few-layer 2M-WS2
a,b, Temperature dependence of the normalized resistance of a 2M-WS2 device (device 01, thickness approximately 4 nm) measured under various out-of-plane and in-plane (along the a axis of the 2M-WS2 crystal) magnetic fields, (a), under out-of-plane magnetic fields. (b), under in-plane magnetic fields. Under zero magnetic field, the device goes to superconducting at TC = 7.6 K, where TC is defined as the temperature corresponding to 50% RN. Inset in (b): schematic configuration of the angular-dependent magnetoresistance measurement. θ denotes the angle between the out-of-plane magnetic field and the positive direction of x axis (the magnetic field rotates in the x–z plane, and the x axis is also the a axis of the 2M-WS2 crystal). γ is defined as the angle between the in-plane magnetic field and the positive direction of the x axis. c, Temperature-dependent critical magnetic field BC2 of the device for the magnetic field along the out-of-plane (BC2⊥\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$B_{{\mathrm{C2}}}^ \bot$$\end{document}, θ = 90°) and in-plane directions (BC2∣∣\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$B_{{\mathrm{C2}}}^{||}$$\end{document}, θ = 0°, γ = 0°). The violet dashed line is the linear fit to BC2⊥=Φ0/2πξ021−T/TC\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$B_{{\mathrm{C2}}}^ \bot = {{{{{\varPhi}}}}}_0/2\uppi \xi \left( 0 \right)^2\left( {1 - T/T_{\mathrm{C}}} \right)$$\end{document}. The pink dashed line is the theoretical fit to BC2∥=Φ012/2πξ0dSC1−T/TC\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$B_{{\mathrm{C2}}}^\parallel = {{{{{\varPhi}}}}}_0\sqrt {12} /2\uppi \xi \left( 0 \right)d_{{\mathrm{SC}}}\sqrt {1 - T/T_{\mathrm{C}}}$$\end{document}. d, Normalized magnetoresistance of the device with the magnetic field direction rotating from in-plane to out-of-plane direction (θ varies from 0° to 90°, T = 7.2 K). e, The extracted angular dependence of BC2 fitted by both 2D Tinkham model BC2θsinθ/BC2∥2+BC2θsinθ/BC2⊥=1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left( {\left( {B_{{\mathrm{C2}}}\left( \theta \right)\sin \theta } \right)/B_{{\mathrm{C2}}}^\parallel } \right)^2 + \left| {\left( {B_{{\mathrm{C2}}}\left( \theta \right)\sin \theta } \right)/B_{{\mathrm{C2}}}^ \bot } \right| = 1$$\end{document} (red) and the 3D anisotropic GL model BC2θsinθ/BC2∥2+BC2θsinθ/BC2⊥2=1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left( {\left( {B_{{\mathrm{C2}}}\left( \theta \right)\sin \theta } \right)/B_{{\mathrm{C2}}}^\parallel } \right)^2 + \left( {\left( {B_{{\mathrm{C2}}}\left( \theta \right)\sin \theta } \right)/B_{{\mathrm{C2}}}^ \bot } \right)^2 = 1$$\end{document} (green). Inset: a magnified view of the region around θ = 0°. f, Current–voltage relation of a 2D 2M-WS2 device (device 02, thickness approximately 4 nm) at various temperatures plotted on a logarithmic scale. The solid black line corresponds to V ∝ I³. Inset: power-law exponent α (extracted by fitting the data in e to the power law V ∝ Iα) as a function of temperature, where a BKT transition temperature TBKT = 5 K is obtained.
Source data

Two-dimensional superconductivity in few-layer 2M-WS2 a,b, Temperature dependence of the normalized resistance of a 2M-WS2 device (device 01, thickness approximately 4 nm) measured under various out-of-plane and in-plane (along the a axis of the 2M-WS2 crystal) magnetic fields, (a), under out-of-plane magnetic fields. (b), under in-plane magnetic fields. Under zero magnetic field, the device goes to superconducting at TC = 7.6 K, where TC is defined as the temperature corresponding to 50% RN. Inset in (b): schematic configuration of the angular-dependent magnetoresistance measurement. θ denotes the angle between the out-of-plane magnetic field and the positive direction of x axis (the magnetic field rotates in the x–z plane, and the x axis is also the a axis of the 2M-WS2 crystal). γ is defined as the angle between the in-plane magnetic field and the positive direction of the x axis. c, Temperature-dependent critical magnetic field BC2 of the device for the magnetic field along the out-of-plane (BC2⊥\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$B_{{\mathrm{C2}}}^ \bot$$\end{document}, θ = 90°) and in-plane directions (BC2∣∣\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$B_{{\mathrm{C2}}}^{||}$$\end{document}, θ = 0°, γ = 0°). The violet dashed line is the linear fit to BC2⊥=Φ0/2πξ021−T/TC\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$B_{{\mathrm{C2}}}^ \bot = {{{{{\varPhi}}}}}_0/2\uppi \xi \left( 0 \right)^2\left( {1 - T/T_{\mathrm{C}}} \right)$$\end{document}. The pink dashed line is the theoretical fit to BC2∥=Φ012/2πξ0dSC1−T/TC\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$B_{{\mathrm{C2}}}^\parallel = {{{{{\varPhi}}}}}_0\sqrt {12} /2\uppi \xi \left( 0 \right)d_{{\mathrm{SC}}}\sqrt {1 - T/T_{\mathrm{C}}}$$\end{document}. d, Normalized magnetoresistance of the device with the magnetic field direction rotating from in-plane to out-of-plane direction (θ varies from 0° to 90°, T = 7.2 K). e, The extracted angular dependence of BC2 fitted by both 2D Tinkham model BC2θsinθ/BC2∥2+BC2θsinθ/BC2⊥=1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left( {\left( {B_{{\mathrm{C2}}}\left( \theta \right)\sin \theta } \right)/B_{{\mathrm{C2}}}^\parallel } \right)^2 + \left| {\left( {B_{{\mathrm{C2}}}\left( \theta \right)\sin \theta } \right)/B_{{\mathrm{C2}}}^ \bot } \right| = 1$$\end{document} (red) and the 3D anisotropic GL model BC2θsinθ/BC2∥2+BC2θsinθ/BC2⊥2=1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left( {\left( {B_{{\mathrm{C2}}}\left( \theta \right)\sin \theta } \right)/B_{{\mathrm{C2}}}^\parallel } \right)^2 + \left( {\left( {B_{{\mathrm{C2}}}\left( \theta \right)\sin \theta } \right)/B_{{\mathrm{C2}}}^ \bot } \right)^2 = 1$$\end{document} (green). Inset: a magnified view of the region around θ = 0°. f, Current–voltage relation of a 2D 2M-WS2 device (device 02, thickness approximately 4 nm) at various temperatures plotted on a logarithmic scale. The solid black line corresponds to V ∝ I³. Inset: power-law exponent α (extracted by fitting the data in e to the power law V ∝ Iα) as a function of temperature, where a BKT transition temperature TBKT = 5 K is obtained. Source data

Source publication
Article
Full-text available
The investigation of two-dimensional atomically thin superconductors—especially those hosting topological states—attracts growing interest in condensed-matter physics. Here we report the observation of spin–orbit–parity coupled superconducting state in centrosymmetric atomically thin 2M-WS2, a material that has been predicted to exhibit topological...

Similar publications

Article
Full-text available
Layered α-RuCl3 is a promising material to potentially realize the long-sought Kitaev quantum spin liquid with fractionalized excitations. While evidence of this state has been reported under a modest in-plane magnetic field, such behaviour is largely inconsistent with theoretical expectations of spin liquid phases emerging only in out-of-plane fie...

Citations

... [1][2][3][4] In two-dimensional (2D) superconductors, however, spin-orbit coupling becomes more significant, accompanied by stronger quantum fluctuations. [5][6][7] In onedimensional (1D) superconductors, electron correlations are further enhanced, deviating from the quasiparticle behavior described by Fermi liquid theory and instead being characterized by Luttinger liquid theory, where the electron pairing mechanism is strongly influenced by Umklapp scattering. [8][9][10] As the dimensionality of superconductivity is lowered from 3D to 1D, both the pairing mechanism and key superconducting parameters are altered, which significantly affect their performance in application. ...
Article
Full-text available
The interplay between dimensionality and superconductivity is a central theme in understanding the behavior of low-dimensional superconductors. In this work, we investigate the dimensional crossover from quasi-two-dimensional (quasi-2D) to three-dimensional (3D) superconductivity in (Li,Fe)OHFeSe1−xSx single crystals driven by sulfur doping. Through detailed structural, electrical, and magnetic characterization, we identify a critical doping level (x = 0.53) where the system transitions from quasi-2D to 3D superconducting behavior. Reduced superconducting fluctuations and non-Fermi liquid behavior near this critical point suggest the presence of competition between intralayer and interlayer pairing mechanisms. Fluctuation conductivity analysis reveals that the coherence length along the c-axis, ζc(0), and the interlayer coupling strength, Γ, increase significantly at x = 0.53, marking the onset of 3D superconductivity. These findings provide new insights into the role of dimensionality and interlayer coupling in modulating superconducting properties, positioning (Li,Fe)OHFeSe1−xSx as a unique platform for exploring crossover physics in iron-based superconductors.
... In the past two decades, 2D materials have attracted significant attention following the discovery of graphene and its exceptional properties [22]. These materials, known for their high surface area, electronic activity, and unique characteristics compared to bulk materials, are ideal for nanostructured modifications. ...
Article
Full-text available
The emergence of two-dimensional transition metal carbides/nitrides (MXene) has attracted extensive research interest. With a unique two-dimensional layered structure, MXene has a large specific surface area, excellent electrical conductivity, high mechanical strength and good stability, which make it highly promising in hydrogen storage and catalysis. It acts as a promising hydrogen storage material and improves the hydrogen storage capacity of metallic substrates, thus advancing the development of efficient and safe hydrogen storage systems. This review focuses on the structural features of MXene and clarifies their effects on hydrogen storage and catalytic performance. The preparation methods of MXene and its applications in hydrogen storage are also discussed. Moreover, the future prospects for MXene-based hydrogen storage materials are outlined, and the current bottlenecks and challenges in the development of MXene for hydrogen storage are explored. The insights from this review highlight the potential of MXene to address critical issues in hydrogen storage, such as low capacity and poor cycling stability, and provide guidance for future research to optimize synthesis processes and enhance the performance of MXene-based materials for practical applications.
... Its close relative, 2M-WS 2 , which has undergone more extensive studies, harbors topological surface states 26,27 as well as Majorana-bound states within its vortex cores 28,29 . Additionally, 2M-WS 2 was identified as an exotic spin-orbit-parity coupled superconductor 25 , responsible for features such as a two-fold symmetric superconducting state and an exceptionally high upper critical magnetic field, i.e., that surpasses the Pauli paramagnetic limit. These unique attributes have spurred immense interest in transition metal dichalcogenides at the intersection of topology and superconductivity 21,22 . ...
Article
Full-text available
Transition metal dichalcogenides display a high technological potential due to their wide range of electronic ground states. Here, we unveil that by tuning hydrostatic pressure P, a cascade of electronic phase transitions can be induced in the few-layer transition metal dichalcogenide 1T’-WS2. As P increases, we observe the suppression of superconductivity with the concomitant emergence of an anomalous Hall effect (AHE) at P1.15P\approx 1.15 GPa. Above 1.6GPa, we uncover a reentrant superconducting state emerging from a state still exhibiting AHE. This superconducting state competes with the AHE state and shows a marked increase in superconducting anisotropy with respect to the ambient pressure phase, suggesting a distinct pairing symmetry. We demonstrate that 1T’-WS2 concomitantly transitions into a strong topological phase with different band orbital characters and Fermi surfaces contributing to the superconductivity. These findings position 1T’-WS2 as a tunable superconductor, wherein superconductivity, AHE, and band features can be tuned reversibly.
... Historically, research on cold atom optical lattices has primarily focused on atoms in the s-band of optical lattices due to experimental limitations [9][10][11][12][13][14][15][16][17][18][19][20][21][22]. However, recent advances have allowed the exploration of atoms in higher bands, such as p-and d-bands, opening new avenues for studying quantum phenomena like orbital physics [23][24][25][26][27], unconventional superfluidity [28][29][30], complex interaction dynamics [31][32][33] and superconductivity [34][35][36][37][38]. ...
Preprint
Full-text available
We propose an experimental scheme to load ultracold Fermi gases from the ground orbital band of a one-dimensional optical lattice into the first excited orbital band. Unlike the narrow momentum distribution of a Bose-Einstein Condensate, Fermi gases exhibit a broad momentum distribution. To address this, we define the average loading efficiency across all quasi-momentum states and theoretically perform the loading operation simultaneously for each Bloch state. Using a multiparameter global optimization method, we determine the loading efficiency at various lattice depths. We can enhance the loading efficiency by adjusting the phase of the lattice, which leverages the different symmetries of Bloch wavefunctions in various optical lattice orbitals. We also identified that the primary factor hindering higher loading efficiency in the Fermi gas is the multiple occupancy of the quasi-momentum states. Our simulations of various occupancies revealed a decreasing trend in mean loading efficiency as the number of occupied quasi-momentum states increases. Finally, we compare our method with other loading techniques and assess its experimental feasibility.
... Since the spin texture in Fig. 1(b) Hc if vortices move freely, the observed results in EuOx/KTO are independent of the current direction (Fig. S9). More recently, two-fold Hc modulations have been ascribed to anisotropic spin susceptibilities that result from 3D spin textures of the Fermi surface due to broken mirror symmetries, and the interplay of parity with spin-orbit coupling near band-inversion points in reciprocal space [36][37][38] . However, experimental evidence for these spin textures in the normal state is not well established. ...
Preprint
Full-text available
Two-dimensional superconductors with spin-textured Fermi surfaces can be a platform for realizing unconventional pairing and are of substantial interest in the context of quantum information science, and superconducting spintronics/orbitronics. We find that the superconducting 2D electron gas (2DEG) formed at EuOx/KTaO3 (110) interfaces, where the EuOx is magnetic, has a spin-texture with an unusual in-plane Ising like uniaxial anisotropy that is revealed in measurements of the in-plane critical field in the superconducting state, as well as from quantum corrections to the magnetoresistance in the normal state. This spin texture is not evident in AlOx/KTaO3 (110) where the overlayer is non-magnetic. Our results are consistent with a highly anisotropic spin-textured Fermi surface in 2DEGs formed at the KTaO3 (110) interface that is hidden from external magnetic fields due to a near cancellation between orbital and spin moments but revealed by exchange interactions of the electrons in the 2DEG with Eu moments near the EuOx/KTaO3 (110) interface. Our findings demonstrate that magnetic overlayers provide a unique probe of spin textures and related phenomena in heterostructures.
... 11,12 Thus, anisotropic TMDs with low symmetry in crystal structure represent a promising platform for investigating novel phenomena such as charge density waves 13 and topological phases. 14,15 Recently, 2M phase WS 2 (2M-WS 2 ), [16][17][18][19][20][21][22][23][24] characterized by its monoclinic crystal structure, exhibits remarkable anisotropic properties. For instance, vortex structures in 2M-WS 2 are highly elongated along W-W zigzag chains, with Majorana bound states exhibiting significant directional anisotropy. ...
... 24 Magnetotransport further highlights a strong anisotropic superconducting gap depending on the magnetic field direction. 23 Additionally, in-plane anisotropic plasmons have been detected in the far-and mid-infrared regimes. 18 Despite these advances, the anisotropic properties of 2M-WS 2 , particularly in electron-phonon coupling and lattice vibration modes, being critical factors 22 in understanding its unconventional superconductivity, remain underexplored. ...
Preprint
Full-text available
Anisotropic materials with low symmetries hold significant promise for next-generation electronic and quantum devices. 2M-WS2, a candidate for topological superconductivity, has garnered considerable interest. However, a comprehensive understanding of how its anisotropic features contribute to unconventional superconductivity, along with a simple, reliable method to identify its crystal orientation, remains elusive. Here, we combine theoretical and experimental approaches to investigate angle- and polarization-dependent anisotropic Raman modes of 2M-WS2. Through first-principles calculations, we predict and analyze phonon dispersion and lattice vibrations of all Raman modes in 2M-WS2. We establish a direct correlation between their anisotropic Raman spectra and high-resolution transmission electron microscopy images. Finally, we demonstrate that anisotropic Raman spectroscopy can accurately determine the crystal orientation and twist angle between two stacked 2M-WS2 layers. Our findings provide insights into the electron-phonon coupling and anisotropic properties of 2M-WS2, paving the way for the use of anisotropic materials in advanced electronic and quantum devices.
... In recent years, many two-dimensional (2D) superconductors (SCs) have been shown to substantially exceed the Pauli limit (H p ). However, the primary mechanisms governing these enhancements are difficult to assign, as many different mechanisms are possible, including Ising spinorbit coupling (SOC) types I (intervalley [1][2][3]) and II (interorbital [4][5][6]), tilted Ising SOC [7,8], dynamic spinmomentum locking [9], as well as the recently proposed spin-orbit parity coupling (SOPC) [10,11]. For few-layer MoTe 2 , evidence for either SOPC [10] or tilted Ising SOC has been reported [7,8]. ...
... The zero-temperature upper critical fields extracted from the I c data are H kb c2 ð0Þ ¼ 28.9 T, H ka c2 ð0Þ ¼ 14.7 T, consistent with the values extracted from the temperature-dependent critical field data. We note that the anisotropy of the superconducting behavior persists for I c , suggesting an anisotropic response of the superconducting gap with in-plane magnetic field, similar to 2M-WS 2 [11]. ...
Article
Noncentrosymmetric two-dimensional superconductors with large spin-orbit coupling offer an opportunity to explore superconducting behaviors far beyond the Pauli limit. One such superconductor, few-layer T_{d}-MoTe_{2}, has large upper critical fields that can exceed the Pauli limit by up to 600%. However, the mechanisms governing this enhancement are still under debate, with theory pointing toward either spin-orbit parity coupling or tilted Ising spin-orbit coupling. Moreover, ferroelectricity concomitant with superconductivity has been recently observed in the bilayer, where strong changes to superconductivity can be observed throughout the ferroelectric transition pathway. Here, we report the superconducting behavior of bilayer T_{d}-MoTe_{2} under an in-plane magnetic field, while systematically varying magnetic field angle and out-of-plane electric field strength. We find that superconductivity in bilayer MoTe_{2} exhibits a twofold symmetry with an upper critical field maxima occurring along the b axis and minima along the a axis. The twofold rotational symmetry remains robust throughout the entire superconducting region and ferroelectric hysteresis loop. Our experimental observations of the spin-orbit coupling strength (up to 16.4 meV) agree with the spin texture and spin splitting from first-principles calculations, indicating that tilted Ising spin-orbit coupling is the dominant underlying mechanism.
... Ising superconductivity in TMDs, such as 2H-MoS 2 , is generally inplane isotropic 12 . A few exceptions, such as few-layer 1T d -MoTe 2 , 2H-NbSe 2 and 2M-WS 2 , possess in-plane anisotropic Ising-like superconductivity [13][14][15] . The mechanisms underlying this anisotropy have been under debate, with proposals such as anisotropic SOC 13 , competing superconducting order parameters 14 and spin-orbit-parity coupling 15 . ...
... A few exceptions, such as few-layer 1T d -MoTe 2 , 2H-NbSe 2 and 2M-WS 2 , possess in-plane anisotropic Ising-like superconductivity [13][14][15] . The mechanisms underlying this anisotropy have been under debate, with proposals such as anisotropic SOC 13 , competing superconducting order parameters 14 and spin-orbit-parity coupling 15 . Hence, data from additional in-plane anisotropic Ising superconductors would help to unravel this puzzle. ...
... In all the devices, H == c2 exceeds the Pauli limit for both B // directions, demonstrating nematic Ising superconductivity in the materials. The in-plane anisotropy obtained from H == c2, max =H == c2, min ranges from~2.6 to 6.5, which is much larger than previous results of Ising-like superconductors [13][14][15] . Additionally, nematic behavior is observed throughout the superconducting state of 6R-TaS 2 , in contrast to the isotropic behavior observed in the ultra-low T regime of another vdWHs 4H b -TaS 2 6 . ...
Article
Full-text available
In van der Waals heterostructures (vdWHs), the manipulation of interlayer stacking/coupling allows for the construction of customizable quantum systems exhibiting exotic physics. An illustrative example is the diverse range of states of matter achieved through varying the proximity coupling between two-dimensional (2D) quantum spin liquid (QSL) and superconductors within the TaS2 family. This study presents a demonstration of the intertwined physics of spontaneous rotational symmetry breaking, hidden magnetism, and Ising superconductivity (SC) in the three-fold rotationally symmetric, non-magnetic natural vdWHs 6R-TaS2. A distinctive phase emerges in 6R-TaS2 below a characteristic temperature (T*) of approximately 30 K, which is characterized by a remarkable set of features, including a giant extrinsic anomalous Hall effect (AHE), Kondo screening, magnetic field-tunable thermal hysteresis, and nematic magneto-resistance. At lower temperatures, a coexistence of nematicity and Kondo screening with Ising superconductivity is observed, providing compelling evidence of hidden magnetism within a superconductor. This research not only sheds light on unexpected emergent physics resulting from the coupling of itinerant electrons and localized/correlated electrons in natural vdWHs but also emphasizes the potential for tailoring exotic quantum states through the manipulation of interlayer interactions.
... Experimentally, angle-resolved photoemission spectroscopy (ARPES) investigation has observed topological surface states 15,16 and scanning tunneling microscopy/spectroscopy (STM/STS) study has discovered signatures of zero Majorana modes at its magnetic vortex cores 17 , both demonstrating nontrivial band structure topology. In addition, 2M-WS 2 has exhibited a rich phase diagram, featuring Paulilimit violated superconductivity 18,19 , surface charge-ordered states 20 , and strange metal behavior 21 . However, the physical mechanism underlying is far from understood. ...
Article
Full-text available
The interaction between lattice vibrations and electrons plays a key role in various aspects of condensed matter physics — including electron hydrodynamics, strange metal behavior, and high-temperature superconductivity. In this study, we present systematic investigations using Raman scattering and angle-resolved photoemission spectroscopy (ARPES) to examine the phononic and electronic subsystems of the topological superconductor candidate 2M-WS2. Raman scattering exhibits an anomalous nonmonotonic temperature dependence of phonon linewidths, indicative of strong phonon–electron scattering over phonon–phonon scattering. The ARPES results demonstrate pronounced dispersion anomalies (kinks) at multiple binding energies within both bulk and topological surface states, indicating a robust and mode-selective coupling between the electronic states and various phonon modes. These experimental findings align with previous calculations of the Eliashberg function, providing a deeper understanding of the highest superconducting transition temperature observed in 2M-WS2 (8.8 K) among all transition metal dichalcogenides as induced by electron–phonon coupling. Furthermore, our results may offer valuable insights into other properties of 2M-WS2 and guide the search for high-temperature topological superconductors.
... Evidently, this structural arrangement signifies a six-fold rotational symmetry. Fig.1b shows the calculated energy band of the kagome superconductor, highlighting an important feature near the Fermi energy: the parity mixing between the d-orbital of the V atom and the p-orbital of the Sb atom, introducing a spin-orbit-parity-coupling term [52,53] in contrast to the conventional spin-orbitcoupling term. In the two-dimensional limit, this spin-orbit-parity-coupling term is responsible for the observation of the two-fold symmetric in-plane upper critical field in this centrosymmetric material [52,53] which exhibits a nematic normal state 14 . ...
... Fig.1b shows the calculated energy band of the kagome superconductor, highlighting an important feature near the Fermi energy: the parity mixing between the d-orbital of the V atom and the p-orbital of the Sb atom, introducing a spin-orbit-parity-coupling term [52,53] in contrast to the conventional spin-orbitcoupling term. In the two-dimensional limit, this spin-orbit-parity-coupling term is responsible for the observation of the two-fold symmetric in-plane upper critical field in this centrosymmetric material [52,53] which exhibits a nematic normal state 14 . In Fig. 1c, we present the current-voltage curves of the device at different temperatures, showcasing a characteristic superconducting behavior. ...
... As shown in the theoretical calculations ( Fig. S3b) within the single-layer limit, the presence of the nematic order and the spin-orbit-parity-coupling (SOPC) [52,53] can lead to a two-fold symmetric upper critical field (details can be found in the Supplementary Information) even when the orbital effects of the in-plane magnetic field is ignored. Due to the finite thickness of the sample, the orbital effects of the magnetic field can also induce this two-fold symmetry [57,58], given the six-fold rotational symmetry is broken by the nematic order in the normal state 14 . ...
Preprint
Full-text available
The study of kagome materials has attracted much attention in the past few years due to the presence of many electron-electron interaction-driven phases in a single material.In this work, we report the discovery of intrinsic spin-polarized p-wave superconductivity in the thin-flake kagome material RbV3_3Sb5_5. Firstly, when an in-plane magnetic field is swept in opposite directions, we observe a unique form of hysteresis in magnetoresistance which is different from the hysteresis induced by extrinsic mechanisms such as flux-trapping or superheating and supercooling effects. The unconventional hysteresis indicates the emergence of an intrinsic time-reversal symmetry-breaking superconducting phase. Strikingly, at a fixed magnetic field, the finite-resistance state can be quenched to the zero-resistance state by applying a large current. Secondly, at temperatures around 400 mK, the re-entrance of superconductivity occurs during an in-plane field-sweeping process with a fixed sweeping direction. This kind of re-entrance is asymmetric about the zero field axis and observed in all field directions for a fixed current direction, which is different from the re-entrance observed in conventional superconductors. Moreover, the angle-dependent in-plane critical field measurements reveal a two-fold symmetry that deviates from the original, centrosymmetric D6h_{6h} point group symmetry of the crystal. These findings put very strong constraints on the possible superconducting pairing symmetry of RbV3_3Sb5_5. We point out that the pairing symmetry, which is consistent with the crystal symmetry and all the observed novel properties, is a time-reversal symmetry-breaking, p-wave pairing with net spin polarization. Importantly, this p-wave pairing gives rise to a nodal topological superconducting state with Majorana flat bands on the sample edges.