Superconducting order from disorder in 2H-TaSe 2− x S x

Abstract

We report on the emergence of robust superconducting order in single crystal alloys of TaSe 2−x S x (0 ≤ × ≤ 2). The critical temperature of the alloy is surprisingly higher than that of the two end compounds TaSe 2 and TaS 2 . The evolution of superconducting critical temperature T c (x) correlates with the full width at half maximum of the Bragg peaks and with the linear term of the high-temperature resistivity. The conductivity of the crystals near the middle of the alloy series is higher or similar than that of either one of the end members 2H-TaSe 2 and/or 2H-TaS 2 . It is known that in these materials superconductivity is in close competition with charge density wave order. We interpret our experimental findings in a picture where disorder tilts this balance in favor of superconductivity by destroying the charge density wave order.npj Quantum Materials (2017) 2:11 ; doi:10.1038/s41535-017-0016-9 INTRODUCTIONThe interplay of disorder and interactions is a fruitful area of investigation. In the absence of electron-electron interactions, disorder can turn a metallic system into an Anderson insulator, 1 but can remain metallic when interactions are important. The additional complexity of competing orders such superconductivity with charge density wave (CDW) or magnetism makes this problem one of the most challenging frontiers in physics. 2-5 A large body of literature is devoted to this interplay in nearly magnetic materials. 6 The interplay of disorder and superconductivity in CDW materials have been less explored than its magnetic analog.Superconductivity and CDW are traditionally viewed as weakcoupling Fermi surface instabilities due to electron-phonon coupling. 7 Arguments have been made both for their cooperation and competition. 8,9 Hexagonal transition metal dichalcogenide 2H-TaSe 2 (P63/mmc space group) undergoes a second-order transition to an incommensurate CDW at 122 K followed by a first-order lock-in transition to a commensurate CDW (CCDW) phase at 90 K, eventually becoming superconducting below 0.14 K upon cooling. 10, 11 2H-TaS 2 has T c = 0.8 K below an in-plane CCDW at 78 K. 10,12 The CDW mechanism in 2H-TaSe 2 involves an electron instability in the bands nested away from the Fermi surface, whereas 2H-TaS 2 features a polar charge and orbital order. 13,14 CDW in 2H-TaSe 2 is dominated by hopping between next-nearest neighbors that creates three weakly coupled triangular sublattices. 15 It is of interest to note that the 2H-TaSe 2 is quasi-twodimensional (2D) metal with pseudogap and with c-axis resistivity 25-50 times higher than the in-plane resistivity, i.e., ρ c (T) >> ρ ab (T). 10,13,[16][17][18] Here, we report that in the 2H-TaSe 2−x S x alloy series the CDW is suppressed and the superconductivity is maximized with

Emergent superconductivity upon disordering a charge density wave ground state

“…For example, by applying pressure in 1T-TaSe 2 [38], doping with Se [39] one observes similar phenomena. Also the 2H polytype of the TaSe 2 shows similar transitions by Cu doping [40], introducing crystallographic disorder by intercalating Se [41], and irradiation induced defects [27]. Many other TMDs like 2H-NbSe 2 [42], 2H-TaSe 2 and even cuprates [4] follow more or less a similar trend.…”

Mitigation of readout noise in near-term quantum devices by classical post-processing based on detector tomography

“…However, if one really hopes for utilizing such near-term devices for real-life applications like quantum computation [6] or quantum simulations [7], experimental imperfections must be taken into account. Hence, to properly characterize noise occurring in the devices and to develop error correction and mitigation schemes that may help to fight it have become tasks of fundamental importance [8][9][10][11][12][13]. In the present work, we address this problem for the noise affecting quantum measurements.…”

“…We will now comment on related works. There is a variety of recent research concerning mitigation of different types of errors in the contemporary quantum devices [8][9][10][11][12][13]. In particular, in the works [9,10], the classical postprocessing of the data was used to mitigate 'assignment errors', which may refer to the related procedure.…”

3D Starfish‐Like FeOF on Graphene Sheets: Engineered Synthesis and Lithium Storage Performance

“…[8a, 10a, 23] Upon charging, am ajor oxidation peak at about 2.5 V, with a very smalls houldera ta bout 3.15 V, is observed, which may be ascribed to the conversion and intercalation reactions, respectively.Aclear positive shift in the cathodic( lithiation) peaks (2.4!2.8 Va nd 1.2!2.0 V) in subsequent cycles can be observed, as ac onsequenceo fm orphology and compositional changes after the first cycle;t his is commonly observed behavior for iron oxyfluoride based cathodes. [13,17,24] From the second cycle onwards, the CV profiles remains teady and overlap well, which indicates the excellent reversibility of the FeOF/rGO electrode. In contrast, ac lear decline was observed from the second to fifth cyclesf or bare FeOF ( Figure S7 in the Supporting Information).…”