Superconductivity and topological aspects of the rocksalt carbides NbC and TaC

Shang, T.; Zhao, Jianzhou; Gawryluk, D. J.; Shi, M.; Medarde, M.; Pomjakushina, E.; Shiroka, T.

doi:10.1103/physrevb.101.214518

Cited by 42 publications

(44 citation statements)

References 59 publications

(73 reference statements)

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“…Recently, some Transition metal carbides (TMCs) viz. TaC [22,23], NbC [23,24] are found to have DSM-like band structures along with bulk superconductivity. Superconductivity of these materials was observed a long time ago and is summarized in a combined report on Superconductivity of TMCs [25], but their topologically non-trivial character was not explored.…”

Section: Introductionmentioning

confidence: 99%

“…Other TMCs, such as VC [26] and CrC [26], are also predicted to have nontrivial band topology along with bulk superconductivity, but experimental confirmation of their non-trivial topological behavior is yet to be realized. Among these TMCs, the NbC and TaC show superconductivity in range of 8 to 11K [22][23][24][27][28][29]. Most of the Superconductivity reports of these materials are based on polycrystalline samples, as it is difficult to grow their single crystals.…”

Section: Introductionmentioning

confidence: 99%

“…The superconducting critical temperature (T c ) of polycrystalline NbC varies with the lattice parameter [28], due to variation in stoichiometry of Carbon [30,31]. Non-trivial band topology in NbC was recently predicated theoretically through DFT calculations [23,24]. In a very recent report on single crystalline NbC being synthesized using Co as flux [24], the Angle-Resolved Photoelectron Spectroscopy (ARPES) measurements showed clear Fermi surface nesting as the origin of non-trivial band topology in NbC.…”

Section: Introductionmentioning

confidence: 99%

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Superconductivity with Topological Non-trivial Surface States in NbC

Karn

Sharma

et al. 2021

J Supercond Nov Magn

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Quantum materials with non-trivial band topology and bulk superconductivity are considered superior materials to realize topological superconductivity. In this regard, we report detailed Density Functional Theory (DFT) calculations for NbC superconductor which shows the topologically non-trivial band structure. Bulk superconductivity at 8.9K is confirmed through DC magnetization measurements under Field Cooled (FC) and Zero Field Cooled (ZFC) protocols. This superconductivity is found to be of type-II nature as revealed by isothermal M-H measurements and thus calculated the Ginzberg-Landau parameter. A large intermediate state is evident from phase diagram, showing NbC to be a strong type-II superconductor. When compared with earlier reports on superconducting NbC, a non-monotonic relationship of critical temperature with lattice parameters is seen. In conclusion, it is clear that NbC is a type-II around 10K superconductor with topological non-trivial surface states.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Superconductivity with Topological Non-trivial Surface States in NbC

Karn

Sharma

et al. 2021

J Supercond Nov Magn

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“…Recently, experimental studies performed on theoretically predicted topological binary and ternary superconducting compounds such as NbC, TaC [13], and A15 Ti 3 X (X = Ir, Sb) [14,15], ZrRuAs [16], and kagome flat-band LaRu 3 Si 2 [17] have shown conventional s-wave superconductivity with preserved time-reversal symmetry (TRS). In contrast, multigap superconductivity has been reported in the topological superconducting candidate TaOsSi [18] and TRS is preserved.…”

Section: Introductionmentioning

confidence: 99%

Superconducting ground state of the nonsymmorphic superconducting compound Zr2Ir

et al. 2021

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The nonsymmorphic Zr 2 Ir alloy is a possible topological semimetal candidate material and as such may be part of an exotic class of superconductors. Zr 2 Ir is a superconductor with a transition temperature of 7.4 K with critical fields of 19.6(3) mT and 3.79(3) T, as determined by heat capacity and magnetization. Zero-field muon spin relaxation measurements show that time-reversal symmetry is preserved in these materials. The specific heat and transverse field muon spin rotation measurements rule out any possibility to have a nodal or anisotropic superconducting gap, revealing a conventional s-wave nature in the superconducting ground state. Therefore this system is found to be a conventional nonsymmorphic superconductor, with time-reversal symmetry being preserved and an isotropic superconducting gap.

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“…Recently, several theoretical and experimental works on this material found evidence for a topological band structure and possible unconventional superconductivity. These findings generated renewed interest in NbC in quantum material research [22,23].…”

Section: Introductionmentioning

confidence: 99%

Direct observation of the scaling relation between density of states and pairing gap in a dirty superconductor*

Zhu¹,

Liu²,

Song³

et al. 2021

Chinese Phys. B

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Theories and experiments on "dirty superconductors" are sophisticated but important for both fundamentals and applications. It becomes more challenging when magnetic fields are present, because the field distribution, the electron density of states, and the superconducting pairing potentials are nonuniform. Here we present tunneling microspectroscopic experiments on NbC single crystals and show that NbC is a homogeneous dirty superconductor. When applying magnetic fields to the sample, we observe that the zero-energy local density of states and the pairing energy gap follow an explicit scale relation proposed by de Gennes for homogeneous dirty superconductors in high magnetic fields. Surprisingly, our experimental findings suggest that the validity of the scale relation extends to magnetic field strengths far below the upper critical field and call for new nonperturbative understanding of this fundamental property in dirty superconductors. On the practical side, we use the observed scale relation to drive a simple and straightforward experimental scheme for extracting the superconducting coherence length of a dirty superconductor in magnetic fields.

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Superconductivity and topological aspects of the rocksalt carbides NbC and TaC

Cited by 42 publications

References 59 publications

Superconductivity with Topological Non-trivial Surface States in NbC

Superconductivity with Topological Non-trivial Surface States in NbC

Superconducting ground state of the nonsymmorphic superconducting compound Zr2Ir

Direct observation of the scaling relation between density of states and pairing gap in a dirty superconductor*

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