Analog of the Anderson Theorem for the Polar Phase of Liquid 3He in a Nematic Aerogel

Фомин, И. А.

doi:10.1134/s106377611811002x

Cited by 46 publications

(35 citation statements)

References 20 publications

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“…We also note that the results in Table III suggest that the effects of disorder on unconventional pairing states depend strongly on the microscopic nature of disorder (we note that a similar disorder dependent pair-breaking rate has been argued to exist in superfluid 3 He in a nematic aerogel [81]). This opens an interesting avenue to manipulate the superconducting ground state by selectively inducing specific types of disorder potentials.…”

Section: Discussionmentioning

confidence: 57%

Effect of interorbital scattering on superconductivity in doped Dirac semimetals

Dentelski

Kozii

Ruhman

2020

Phys. Rev. Research

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Unconventional superconductivity has been discovered in a variety of doped quantum materials, including topological insulators and semimetals. A unifying property of these systems is strong orbital hybridization, which leads to pairing of states with nontrivial Bloch wave functions. In contrast to naive expectation, however, many of these superconductors are relatively resilient to disorder. Here we study the interplay of superconductivity and disorder in doped three-dimensional Dirac systems, which serve as a paradigmatic dispersion in quantum materials, using Abrikosov-Gor'kov theory. In this way, the role of disorder is captured by a single parameter , the pair scattering rate. In contrast to previous studies, we argue that interorbital scattering cannot be neglected due to the strong orbital hybridization in Dirac systems. We find that the robustness of different pairing states highly depends on the relative strength of the different interorbital scattering channels. In particular, we find that the "nematic" superconducting state, which is argued to be the ground state in many Bi 2 Se 3-related compounds, is not protected from disorder in any way. The pair scattering rate in this case is at best smaller by a factor of 3 compared to systems without spin-orbit coupling. We also find that the odd-parity pairing state with total angular momentum zero (the B phase of superfluid 3 He) is protected against certain types of disorder, which include a family of time-reversal odd (magnetic) impurities. Namely, this odd-parity state is a singlet of partners under CT symmetry (rather than T symmetry in the standard Anderson's theory), where C and T are chiral and time-reversal symmetries, respectively. As a result, it is protected against any disorder potential that respects CT symmetry. Our procedure is very general and can be readily applied to different band structures and disorder configurations.

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Section: Discussionmentioning

confidence: 57%

Effect of interorbital scattering on superconductivity in doped Dirac semimetals

Dentelski

Kozii

Ruhman

2020

Phys. Rev. Research

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“…In our samples, the phase transition with the highest critical temperature always occurs between the normal phase and the polar phase. 77 The order parameter of the polar phase can be written as…”

Section: Polar Phasementioning

confidence: 99%

Half-quantum vortices and walls bounded by strings in the polar-distorted phases of topological superfluid 3He

et al. 2019

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Symmetries of the physical world have guided formulation of fundamental laws, including relativistic quantum field theory and understanding of possible states of matter. Topological defects (TDs) often control the universal behavior of macroscopic quantum systems, while topology and broken symmetries determine allowed TDs. Taking advantage of the symmetry-breaking patterns in the phase diagram of nanoconfined superfluid 3He, we show that half-quantum vortices (HQVs)—linear topological defects carrying half quantum of circulation—survive transitions from the polar phase to other superfluid phases with polar distortion. In the polar-distorted A phase, HQV cores in 2D systems should harbor non-Abelian Majorana modes. In the polar-distorted B phase, HQVs form composite defects—walls bounded by strings hypothesized decades ago in cosmology. Our experiments establish the superfluid phases of 3He in nanostructured confinement as a promising topological media for further investigations ranging from topological quantum computing to cosmology and grand unification scenarios.

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“…For a long time it was presumed that the Anderson theorem is not applicable to spin triplet superconductors, or to superconductors with nodes in the gap. However, it was found by Fomin [90], that if impurities in the polar phase have the form of infinitely long non-magnetic strands, which are straight and parallel to each other, the transition temperature also coincides with that in the clean limit. The reason is that in the presence of columnar defects the polar phase can be considered as a set of independent 2D superfluids.…”

Section: Anderson-fomin Theoremmentioning

confidence: 96%

$$^3$$He Universe 2020

Volovik

2020

J Low Temp Phys

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Analog of the Anderson Theorem for the Polar Phase of Liquid 3He in a Nematic Aerogel

Cited by 46 publications

References 20 publications

Effect of interorbital scattering on superconductivity in doped Dirac semimetals

Effect of interorbital scattering on superconductivity in doped Dirac semimetals

Half-quantum vortices and walls bounded by strings in the polar-distorted phases of topological superfluid 3He

$$^3$$He Universe 2020

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