Using controlled disorder to probe the interplay between charge order and superconductivity in NbSe2

We study the superconducting instability in disordered non-centrosymmetric monolayers with intrinsic Ising spin-orbit coupling (SOC) subjected to an in-plane Zeeman magnetic field. The pairing interaction contains the channels allowed by crystal symmetry, such that in general, the pairing state is a mixture of singlet and triplet Cooper pairs. The joint action of SOC and Zeeman field selects a specific in-plane d-vector triplet component to couple with the singlets, which gains robustness against disorder through the coupling. The out-of-plane d-vector component, that in the clean case is immune to both the Zeeman field and SOC is obliterated by a very small impurity scattering rate. We formulate the quasi-classical theory of Ising superconductors and solve the linearized Eilenberger equations to obtain the pair-breaking equations that determine the Zeeman field -temperature dependence of the continuous superconducting transition. Our discussion emphasizes how the Zeeman field, SOC and disorder affect the different superconducting order parameters, and we show how the spin-fields inevitably induce odd-frequency pairing correlations. arXiv:1908.11662v1 [cond-mat.supr-con]

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“…Yet, only a slight decrease of T c for dirtier has been reported. A similar phenomenon has been recently reported in for NbSe 2 [42].…”

Section: A Monolayer Transition Metal Dichalcogenidessupporting

confidence: 90%

Ising superconductors: Interplay of magnetic field, triplet channels, and disorder

Möckli

Khodas

2020

Phys. Rev. B

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“…In GdSb x Te 2− x−δ , it is likely that Sb and Te order in the square net, which could contribute to the observed superstructure evolution. The effect of order versus disorder on CDWs has previously been investigated . For example, cation disorder or pure atomic disorder is found to substantially reduce the CDW transition temperature in transition‐metal dichalcogenides.…”

Section: Gdsbxte2−x−δ Crystal Structuresmentioning

confidence: 99%

“…The effect of order versus disorder on CDWs has previously been investigated . For example, cation disorder or pure atomic disorder is found to substantially reduce the CDW transition temperature in transition‐metal dichalcogenides. The effect of disorder on the CDW in GdSb x Te 2− x−δ will be of interest for future studies.…”

Section: Gdsbxte2−x−δ Crystal Structuresmentioning

confidence: 99%

Charge Density Waves and Magnetism in Topological Semimetal Candidates GdSb_xTe₂₋_x₋_δ

et al. 2019

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Many topological semimetals are known to exhibit exceptional electronic properties, which are the fundamental basis for design of novel devices and further applications. Materials containing the structural motif of a square net are known to frequently be topological semimetals. In this work, the synthesis and structural characterization of the square‐net‐based magnetic topological semimetal candidates GdSbxTe2−x−δ (0≤x≤1, δ indicating the vacancy level) are reported. The structural evolution of the series with Sb substitution is studied, finding a transition between a simple tetragonal square‐net structure to complex superstructure formations due to the presence of charge density waves. The structural modulations coincide with a significant modification of the magnetic order. This work thus establishes GdSbxTe2−x−δ as a platform to study the interplay between crystal symmetry, band filling, charge density wave, and magnetism in a topological semimetal candidate.

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“…In this work, we report a striking increase of Tc after proton irradiation in the d-wave cuprate superconductor La1.875Ba0.125CuO4, and a similar, albeit expected, Tc increase in Lu5Ir4Si10, a s-wave superconductor with a strong 1D CDW. Increases of Tc have previously been reported in s-wave dichalcogenides using both argon 68 and electron irradiation, 26,61,69 and possible hints can be found in iron-based superconductors. 70,71 (bottom) In parallel to the increase of Tc, a coexisting order was found to be suppressed in some of these compounds.…”

Section: Fig 7 Irradiation Induced Disorder Increases Tc and Supprementioning

confidence: 74%

Disorder raises the critical temperature of a cuprate superconductor

Leroux

Mishra

Ruff

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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With the discovery of charge density waves (CDW) in most members of the cuprate high temperature superconductors, the interplay between superconductivity and CDW has become a key point in the debate on the origin of high temperature superconductivity. Some experiments in cuprates point toward a CDW state competing with superconductivity, but others raise the possibility of a CDW-superconductivity intertwined order, or more elusive pair-density wave (PDW). Here we have used proton irradiation to induce disorder in crystals of La1.875Ba0.125CuO4 and observed a striking 50% increase of Tc accompanied by a suppression of the CDW. This is in sharp contrast with the behavior expected of a d-wave superconductor for which both magnetic and non-magnetic defects should suppress Tc. Our results thus make an unambiguous case for the strong detrimental effect of the CDW on bulk superconductivity in La1.875Ba0.125CuO4. Using tunnel diode oscillator (TDO) measurements, we find indications for potential dynamic layer decoupling in a PDW phase. Our results establish irradiation-induced disorder as a particularly relevant tuning parameter for the many families of superconductors with coexisting density waves, which we demonstrate on superconductors such as the dichalcogenides and Lu5Ir4Si10. Significance statementThe origin of high-temperature superconductivity remains unknown. Over the past two decades, spatial oscillations of the electronic density known as Charge Density Waves (CDW) have been found to coexist with high-temperature superconductivity in most prominent cuprate superconductors. The debate on whether CDW help or hinder high-temperature superconductivity in cuprates is still ongoing. In principle, disorder at the atomic scale should strongly suppress both high-temperature superconductivity and CDW. In this article however, we find that disorder created by irradiation increases the superconducting critical temperature by 50% while suppressing the CDW order, showing that CDW strongly hinder bulk superconductivity. We provide indications this increase occurs because the CDW could be part of a pairdensity wave frustrating the superconducting coupling between atomic planes.Charge density waves (CDW) are real-space periodic oscillations of the crystal electronic density accompanied by a lattice distortion. In their simplest form, CDW can be described as a Bardeen-Cooper-Schrieffer condensate of electron-hole pairs that breaks the translational symmetry. 1 CDW in cuprate superconductors were first observed in lanthanum based compounds, 2-4 such as La 2−x Ba x CuO 4 (LBCO) around 1/8 hole-doping. 2,4-12 In these La-based cuprates, spin correlations were also found to synchronize with the CDW modulation to form static "stripes" 2 of interlocked CDW and spin density waves (SDW) at a certain temperature below the ordering temperature of the CDW (see Fig. 1).More recently, CDW were shown to be a nearly-universal characteristic in cuprates: a CDW was observed in holedoped YBa 2 Cu 3 O 7−δ (YBCO) 13-19 as well as several others ho...

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Using controlled disorder to probe the interplay between charge order and superconductivity in NbSe2

Cited by 112 publications

References 61 publications

Ising superconductors: Interplay of magnetic field, triplet channels, and disorder

Ising superconductors: Interplay of magnetic field, triplet channels, and disorder

Charge Density Waves and Magnetism in Topological Semimetal Candidates GdSb_xTe₂₋_x₋_δ

Disorder raises the critical temperature of a cuprate superconductor

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Using controlled disorder to probe the interplay between charge order and superconductivity in NbSe2

Cited by 112 publications

References 61 publications

Ising superconductors: Interplay of magnetic field, triplet channels, and disorder

Ising superconductors: Interplay of magnetic field, triplet channels, and disorder

Charge Density Waves and Magnetism in Topological Semimetal Candidates GdSbxTe2−x−δ

Disorder raises the critical temperature of a cuprate superconductor

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Charge Density Waves and Magnetism in Topological Semimetal Candidates GdSb_xTe₂₋_x₋_δ