Probing type-II Ising pairing using the spin-mixing parameter

The immunity of the Ising superconductors to external magnetic fields originates from a spin locking of the paired electrons to an intrinsic Zeeman-like field. The spin-momentum locking in non-centrosymmetric crystalline materials leads to type-I Ising pairing in which the direction of the intrinsic field can be deduced from the spin expectation values. In centrosymmetric crystals, all the states are spin degenerate due to time reversal symmetry, but split by the spin-orbit coupling to orbital doublets. The electron spins locked to the orbitals can form Ising type-II pairs. We present an efficient approach to determine the direction of the intrinsic field using the spin-mixing parameter $b^2$. By means of first principles calculations based on the density functional theory we study monolayer polytype 1T phase transition metal dichalcogenide superconductors PdTe$_2$, NbTe$_2$ and TiSe$_2$. We calculate $b^2$ for individual Fermi pockets crossing the Fermi energy and provide a general picture of possible Ising type-II pairing within the full Brillouin zone.

[1]  K. T. Law,et al.  Spin–orbit–parity coupled superconductivity in atomically thin 2M-WS_2 , 2022, Nature Physics.

[2]  G. Profeta,et al.  Coexisting superconductivity and charge-density wave in hydrogen-doped titanium diselenide via ionic liquid gating-induced protonation , 2022 .

[3]  Hanwen Wang,et al.  Recent progresses in two-dimensional Ising superconductivity , 2021 .

[4]  M. Adam,et al.  Charge density wave phase suppression in 1T-TiSe2 through Sn intercalation , 2021, Nano Research.

[5]  Ding Zhang,et al.  Ising pairing in atomically thin superconductors , 2021, Nanotechnology.

[6]  L. Lei,et al.  Charge-density-wave melted superconductivity in 1T-TiSe2 , 2021, EPL (Europhysics Letters).

[7]  Sangyun Lee,et al.  Tuning the charge density wave quantum critical point and the appearance of superconductivity in TiSe2 , 2021, Physical Review Research.

[8]  Chong Wang,et al.  Ising Superconductivity and Its Hidden Variants , 2021, Accounts of Materials Research.

[9]  Xianfu Wang,et al.  Recent Advances in 2D Superconductors , 2021, Advanced materials.

[10]  M. Zhang,et al.  Synthesis and characterization of 2D transition metal dichalcogenides: Recent progress from a vacuum surface science perspective , 2021 .

[11]  Chong Wang,et al.  Type-II Ising superconductivity and anomalous metallic state in macro-size ambient-stable ultrathin crystalline films. , 2020, Nano letters.

[12]  K. T. Law,et al.  Spin-Orbit-Parity-Coupled Superconductivity in Topological Monolayer WTe_{2}. , 2020, Physical review letters.

[13]  M. Nakano,et al.  Superconducting 3R-Ta1+xSe2 with Giant In-plane Upper Critical Fields. , 2020, Nano letters.

[14]  Chong Wang,et al.  Type-II Ising pairing in few-layer stanene , 2019, Science.

[15]  J. Fabian,et al.  Spin-orbit coupling in elemental two-dimensional materials , 2019, Physical Review B.

[16]  Jian Wang,et al.  Superconductivity and Fermi Surface Anisotropy in Transition Metal Dichalcogenide NbTe 2 , 2019, Chinese Physics Letters.

[17]  Yi Xie,et al.  High Phase Purity of Large‐Sized 1T′‐MoS2 Monolayers with 2D Superconductivity , 2019, Advanced materials.

[18]  Chong Wang,et al.  Type-II Ising Superconductivity in Two-Dimensional Materials with Spin-Orbit Coupling. , 2019, Physical review letters.

[19]  D. Jena,et al.  Thickness dependence of superconductivity in ultrathin NbS2 , 2019, Applied Physics Express.

[20]  X. Duan,et al.  Synthesis of Ultrathin Metallic MTe2 (M = V, Nb, Ta) Single‐Crystalline Nanoplates , 2018, Advanced materials.

[21]  Xiaodong Xu,et al.  Tuning Ising superconductivity with layer and spin–orbit coupling in two-dimensional transition-metal dichalcogenides , 2017, Nature Communications.

[22]  U. Zeitler,et al.  Full superconducting dome of strong Ising protection in gated monolayer WS2 , 2017, Proceedings of the National Academy of Sciences.

[23]  Yong Xu,et al.  Superconductivity in few-layer stanene , 2017, 1712.03695.

[24]  Stefano de Gironcoli,et al.  Advanced capabilities for materials modelling with Quantum ESPRESSO , 2017, Journal of physics. Condensed matter : an Institute of Physics journal.

[25]  Qingsheng Zeng,et al.  High-quality monolayer superconductor NbSe2 grown by chemical vapour deposition , 2017, Nature Communications.

[26]  Q. Xue,et al.  Ising Superconductivity and Quantum Phase Transition in Macro-Size Monolayer NbSe2. , 2017, Nano letters.

[27]  Y. Iwasa,et al.  Highly crystalline 2D superconductors , 2017, 1703.03541.

[28]  B. Min,et al.  Experimental Realization of Type-II Dirac Fermions in a PdTe_{2} Superconductor. , 2016, Physical review letters.

[29]  Guanghou Wang,et al.  Nontrivial Berry phase and type-II Dirac transport in the layered material PdT e 2 , 2016, 1611.08112.

[30]  I. Hamada,et al.  Implementation and Validation of Fully Relativistic GW Calculations: Spin-Orbit Coupling in Molecules, Nanocrystals, and Solids. , 2016, Journal of chemical theory and computation.

[31]  A. Neto,et al.  Controlling many-body states by the electric-field effect in a two-dimensional material , 2016, Nature.

[32]  F. Guinea,et al.  Enhanced superconductivity in atomically thin TaS2 , 2016, Nature Communications.

[33]  K. T. Law,et al.  Ising pairing in superconducting NbSe2 atomic layers , 2015, Nature Physics.

[34]  P. Kim,et al.  Nature of the quantum metal in a two-dimensional crystalline superconductor , 2015, Nature Physics.

[35]  Yasuharu Nakamura,et al.  Superconductivity protected by spin–valley locking in ion-gated MoS2 , 2015, Nature Physics.

[36]  M. Chou,et al.  Charge density wave transition in single-layer titanium diselenide , 2015, Nature Communications.

[37]  K. T. Law,et al.  Evidence for two-dimensional Ising superconductivity in gated MoS2 , 2015, Science.

[38]  D. Hamann.  Optimized norm-conserving Vanderbilt pseudopotentials , 2013, 1306.4707.

[39]  F. Freimuth,et al.  Anisotropy of spin relaxation and transverse transport in metals , 2012, Journal of physics. Condensed matter : an Institute of Physics journal.

[40]  Y. Mokrousov,et al.  Anisotropy of spin relaxation in metals. , 2012, Physical review letters.

[41]  M. May,et al.  Charge-density-wave phase of 1T-TiSe2: the influence of conduction band population. , 2011, Physical review letters.

[42]  A. Williams,et al.  Superconductivity at 2.3 K in the misfit compound (PbSe) 1.16(TiSe2)2 , 2010, 1006.5946.

[43]  L. Forró,et al.  Pressure induced superconductivity in pristine 1T-TiSe2. , 2009, Physical review letters.

[44]  Stefano de Gironcoli,et al.  QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials , 2009, Journal of physics. Condensed matter : an Institute of Physics journal.

[45]  R. Cava,et al.  Anisotropic properties of the layered superconductorCu0.07TiSe2 , 2006, cond-mat/0611310.

[46]  R. Cava,et al.  Superconductivity in CuxTiSe2 , 2006, cond-mat/0606529.

[47]  M. Sigrist.  Introduction to Unconventional Superconductivity , 2005 .

[48]  M. Sigrist,et al.  Spin susceptibility in superconductors without inversion symmetry , 2004, cond-mat/0405179.

[49]  L. Gor’kov,et al.  Superconducting 2D system with lifted spin degeneracy: mixed singlet-triplet state. , 2001, Physical review letters.

[50]  S. Sarma,et al.  SPIN RELAXATION OF CONDUCTION ELECTRONS IN POLYVALENT METALS : THEORY AND A REALISTIC CALCULATION , 1998, cond-mat/9810375.

[51]  S. Nagata,et al.  Superconductivity in the metallic layered compound NbTe2 , 1993 .

[52]  R. Friend,et al.  High-pressure transport properties of TiS2 and TiSe2 , 1982 .

[53]  M. H. V. Maaren,et al.  Some new superconducting group Va dichalcogenides , 1967 .

[54]  Clogston.  Upper limit for the critical field in hard superconductors. [V/sub 2. 95/Ga, NbâSn,VâSi, V/sub 1. 95/ Ga] , 1962 .

[55]  B. Chandrasekhar.  A NOTE ON THE MAXIMUM CRITICAL FIELD OF HIGH‐FIELD SUPERCONDUCTORS , 1962 .

[56]  G. Dresselhaus.  Spin-Orbit Coupling Effects in Zinc Blende Structures , 1955 .

[57]  R. J. Elliott,et al.  Theory of the Effect of Spin-Orbit Coupling on Magnetic Resonance in Some Semiconductors , 1954 .