Superconductivity

There are many different aspects of superconductivity addressed in our Center:

The mechanism of the SIT was studied in MoC thin films and in granular Boron doped diamond (BdD). By studying the MoC thin films we found that the bosonic scenario of the SIT is not universal. Our transport and low – temperature Scanning Tunneling Microscopy (STM) experiments demonstrated that the SIT in MoC thin films follows the Fermionic scenario, instead [1]. Moreover, we observed that the spectral smearing increases substantially with the increasing disorder (decreasing film thickness) [1,2]. Based on our measurements, the theory of Dynes superconductors was developed by Hlubina and Herman [3] which explains the smearing by considering local magnetic moments emerging at the interface between the thin film and the substrate [2].This theory was then successfully applied in the characterization of the complex conductivity in disordered 10 nm thin MoC superconducting films [4]. In BdD we studied the bosonic scenario of the SIT. We found that in this case, the suppression of superconductivity is associated with the loss of global coherence in the Cooper pair condensate [5].

Recently, the SIT in a transverse magnetic field was studied in a highly disordered MoC film with the product of the Fermi momentum and the mean free path kFl close to unity [6]. Surprisingly, the Zeeman paramagnetic effects dominate over orbital coupling on both sides of the transition. In the superconducting state it is evidenced by a high upper critical magnetic field Bc2, by its square-root dependence on temperature, as well as by the Zeeman splitting of the quasiparticle density of states (DOS) measured by scanning tunneling microscopy. At Bc2 a logarithmic anomaly in DOS is observed. This anomaly is further enhanced in an increasing magnetic field, which is explained by the Zeeman splitting of the Altshuler-Aronov DOS driving the system into a more insulating or resistive state. A spin-dependent Altshuler-Aronov correction is also needed to explain the transport behavior above Bc2.

  1. P. Szabó, T. Samuely, V. Hašková, J. Kačmarčík, M. Žemlička, M. Grajcar, J. G. Rodrigo and P. Samuely:
    Fermionic scenario for the destruction of superconductivity in ultrathin MoC films evidenced by STM measurements,
    Phys. Rev. B 93, (2016) 014505
  2. V.Hašková, M.Kopčík, P.Szabó, T.Samuely, J.Kačmarčík, O.Onufriienko, M.Žemlička, P.Neilinger, M.Grajcar, P.Samuely:
    On the origin of in-gap states in homogeneously disordered ultrathin films. MoC case,
    Appl. Surf. Sci.461, (2018) 143
  3. F. Herman and R. Hlubina, Phys. Rev. B 94, (2016) 144508; 95, (2017) 094514, 96, (2017) 014509; 97, (2018) 014517
  4. M. Žemlička, P. Neilinger, M. Trgala, M. Rehák, D. Manca, M. Grajcar, P. Szabó, P. Samuely, Š. Gaži, U. Hübner, V. M. Vinokur, E. Il’ichev: Finite quasiparticle lifetime in disordered superconductors,
    Phys. Rev. B 92 (2015), 224506
  5. G. Zhang, T. Samuely, H. Du, Z. Xu, L. Liu, O. Onufriienko, P. W. May, J. Vanacken, P. Szabó, J. Kačmarčík, H. Yuan , P. Samuely, R. E. Dunin-Borkowski, J. Hofkens, and V. V. Moshchalkov:
    Bosonic Confinement and Coherence in Disordered Nanodiamond Arrays,
    ACS Nano, 11, (2017) 11746
  6. M. Žemlička, M. Kopčík, P. Szabó, T. Samuely, J. Kačmarčík, P. Neilinger, M. Grajcar, P. Samuely:
    Zeeman-driven superconductor-insulator transition in strongly disordered MoC films: Scanning tunneling microscopy and transport studies in a transverse magnetic field,
    Phys. Rev. B 102, 180508(R) 2020
  1. Ch. Marcenat, T Klein, D. LeBoeuf, A. Jaoui, G. Seyfarth, J. Kačmarčík, Y. Kohama, H. Cercellier, H. Aubin, K. Behnia, B. Fauqué:
    Wide Critical Fluctuations of the Field-Induced Phase Transition in Graphite,
    Phys. Rev. Lett. 126, 106801 (2021) , DOI: 10.1103/PhysRevLett.126.106801
  2. B. Michon, C. Girod, S. Badoux, J. Kačmarčík, Q. Ma, M. Dragomir, H. A. Dabkowska, B. D. Gaulin, J.-S. Zhou, S. Pyon, T. Takayama, H. Takagi, S. Verret, N. Doiron-Leyraud, C. Marcenat, L. Taillefer, T. Klein:
    Thermodynamic signatures of quantum criticality in cuprate superconductors,
    Nature, 567 (2019) 2018-222, doi.org/10.1038/s41586-019-0932-x
  3. J. Kačmarčík, I. Vinograd, B. Michon, A. Rydh, A. Demuer, R. Zhou, H. Mayaffre, R. Liang, W. N. Hardy, D. A. Bonn, N. Doiron-Leyraud, L. Taillefer, M. -H. Julien, C. Marcenat, T. Klein:
    Unusual interplay between superconductivity and field-induced charge order in YBa2Cu3Oy
    Physical Review Letters 121 (2018) 167002, doi.org/10.1103/PhysRevLett.121.167002
  4. P. Rodiere, T. Klein, L. Lemberger, K. Hasselbach, A. Demuer, J. Kačmarčík, Z. S. Wang, H. Q. Luo, X. Y. Lu, H. H. Wen, F. Gucmann, and C. Marcenat:
    Scaling of the physical properties in Ba(Fe,Ni)2As2 single crystals: Evidence for quantum fluctuations,
    Phys. Rev. B 85 214506 (2012)
  1. P. Samuely, P. Szabó, J. Kačmarčík, A. Meerschaut, L. Cario, A. G. M. Jansen, T. Cren, M. Kuzmiak, O. Šofranko, and T. Samuely:
    Extreme in-plane upper critical magnetic fields of heavily doped quasi-two-dimensional transition metal dichalcogenides,
    Phys. Rev. B 104, 224507 (2021)
  2. R. T. Leriche, A. Palacio-Morales, M. Campetella, C. Tresca, S. Sasaki, Ch. Brun, F. Debontridder, P. David, I. Arfaoui, O. Šofranko, T. Samuely, G. Kremer, C. Monney, T. Jaouen, L. Cario, M. Calandra, T. Cren:
    Misfit Layer Compounds: A Platform for Heavily Doped 2D Transition Metal Dichalcogenides,
    Adv. Funct. Mater. 2020, 2007706, DOI: 10.1002/adfm.202007706

Mo8Ga41

Superconductivity in Mo8Ga41 was studied by a combination of several experimental methods applied on the same piece of crystal – by STM as a surface sensitive technique, by ac-calorimetry to measure heat capacity as a bulk probe and by local Hall-probe magnetometry. We showed that seemingly two-gap behavior is just a consequence of sample inhomogeneities and is not a reflection of existence of two energy gaps. From the heat capacity measurements it is clearly observed that only one energy gap exists in the quasiparticles spectrum. Minute traces of additional superconducting phases detected by STS and also in the heat capacity measured in high magnetic fields on a high-quality and seemingly single-phase crystal might mimic the multigap superconductivity of Mo8Ga41 suggested recently in several studies.

  1. M. Marcin, J. Kačmarčík, Z. Pribulová, M. Kopčík, P. Szabó, O. Šofranko, T. Samuely, V. Vaňo, Ch. Marcenat, V. Yu. Verchenko, A. V. Shevelkov, P. Samuely:
    Single-gap superconductivity in Mo8Ga41
    Scientific Reports 9, 13552 (2019), doi.org/10.1038/s41598-019-49846-y
  2. M. Marcin, Z. Pribulová, J. Kačmarčík, Z. Medvecká, T. Klein, V. Yu. Verchenko, V. Cambel, J. Šoltýs, P. Samuely:
    One or two gaps in Mo8Ga41 superconductor? Local Hall-probe magnetometry study,
    Supercond. Sci. Technol. 34 (2021) 035017 (5pp), https://doi.org/10.1088/1361-6668/abd5f3

CuxTiSe2

We performed a complex study of a series of TiSe2 crystals intercalated with copper by means of thermodynamic and magnetization measurements [1,2]. We showed that, in spite of some other measurements indicating two-gap superconductivity, the system is a single-gap superconductor. This is also supported by the results of ARPES measurements. Moreover, in [3] we present observation of unexpected effect in the system when superconducting vortices remain locked in between the layers of the sample even in tilted magnetic field. This so-called lock-in effect could be related to observation of the two-gap-like behavior in the superfluid density of the material [1].

  1. Z. Pribulová, Z. Medvecká, J. Kačmarčík, V. Komanický, T. Klein, P. Rodiere, F. Levy-Bertrand, B. Michon, C. Marcenat, P. Husaníková, V.Cambel, J. Šoltýs, G. Karapetrov, S. Borisenko, D. Evtushinsky, H. Berger, P. Samuely:
    Magnetic and thermodynamic properties of CuxTiSe2 single crystals,
    Phys. Rev. B, 95, 174512 (2017)
  2. J. Kačmarčík, Z. Pribulová, V. Paľuchová, P. Szabó, P. Husaníková, G. Karapetrov and P. Samuely:
    Heat capacity of single-crystal CuxTiSe2 superconductors,
    Phys. Rev. B 88 020507(R) (2013)
  3. Z. Medvecká, T. Klein, V. Cambel, J. Šoltýs, G. Karapetrov, F. Levy-Bertrand, B. Michon, C. Marcenat, Z. Pribulová, P. Samuely:
    Observation of a transverse Meissner effect in CuxTiSe2 single crystals
    Phys. Rev. B 93, 100501(R) (2016)

Bi2Pd

  1. J. Kačmarčík, Z. Pribulová, T. Samuely, P. Szabó, V. Cambel, J. Šoltýs, E. Herrera, H. Suderow, A. Correa-Orellana, D. Prabhakaran, and P. Samuely:
    Single-gap superconductivity in Bi2Pd,
    Phys. Rev. B 93, 144502 (2016)
  2. G. Pristáš, Mat. Orendáč, S. Gabáni, J. Kačmarčík, E. Gažo, Z. Pribulová, A. Correa-Orellana, E. Herrera, H. Suderow, P. Samuely:
    Pressure effect on the superconducting and the normal state of ß-Bi2Pd,
    Phys. Rev. B 97 (2018), 134505, DOI: 10.1103/PhysRevB.97.134505

SrPd2Ge2

  1. T. Samuely, P. Szabó, Z. Pribulová, N. H. Sung, B. K. Cho, T. Klein, V. Cambel, J. G. Rodrigo and P. Samuely:
    Type II superconductivity in SrPd2Ge2
    Supercon. Sci. Technol. 26 015010 (2013)

YB6

  1. S. Gabáni, I. Takáčová, G. Pristaš, E. Gažo, K. Flachbart, T. Mori, D. Braithwaite, M. Misek, K.V. Kamenev, M. Hanfland and P. Samuely:
    High-pressure effect on the superconductivity of YB6,
    Phys. Rev. B 90, 045136 (2014)
  2. P. Szabó, J. Girovský, Z. Pribulová, J. Kačmarčík, T. Mori and P. Samuely: Point-contact spectroscopy of the phononic mechanism of superconductivity in YB6
    Supercon. Sci. Technol. 26 045019 (2013)

NbS2

  1. J. Kačmarčík, Z. Pribulová, C. Marcenat, T. Klein, P. Rodiere, L. Cario and P. Samuely:
    Specific heat measurements of a superconducting NbS2 single crystal in an external magnetic field: Energy gap structure
    Phys. Rev. B 82 (2010) 014518

Pnictides

  1. P. Szabó, Z. Pribulová, G. Pristáš, S. L. Bud’ko, P. C. Canfield and P. Samuely:
    Evidence for two-gap superconductivity in Ba0.55K0.45Fe2As2 from directional point-contact Andreev-reflection spectroscopy
    Phys. Rev. B 79 (2009) 012503
  2. P. Samuely, P. Szabó, Z. Pribulová, M.E. Tillman, S.L. Buďko and P.C. Canfield:
    Possible two-gap superconductivity in NdFeAsO0.9F0.1 probed by point-contact Andreev-reflection spectroscopy
    Supercon. Sci. Technol. 22 (2009) 014003
  3. J. Kačmarčík, C. Marcenat, T. Klein, Z. Pribulová, C. J. van der Beek, M. Konczykowski, S. L. Budko, M. Tillman, N. Ni, and P. C. Canfield:
    Strongly dissimilar vortex-liquid regimes in single-crystalline NdFeAs(O,F) and (Ba,K)Fe2As2: A comparative study
    Phys. Rev. B 80 (2009) 014515
  4. Z. Pribulová, T. Klein, J. Kačmarčík, C. Marcenat, M. Konczykowski, S. L. Bud’ko, M. Tillman, and P. C. Canfield:
    Upper and lower critical magnetic fields of superconducting NdFeAsO1-xFx single crystals studied by Hall-probe magnetization and specific heat
    Phys. Rev. B 79 (2009) 020508(R)
  1. A. Grockowiak, T. Klein, H. Cercellier, F. Lévy-Bertrand, X. Blase, J. Kačmarčík, T. Kociniewski, F. Chiodi, D. Débarre, G. Prudon, C. Dubois, and C. Marcenat:
    Thickness dependence of the superconducting critical temperature in heavily doped Si:B epilayers,
    Phys. Rev. B 88 064508 (2013)
  2. C. Marcenat, J. Kačmarčík, R. Piquerel, P. Achatz, G. Prudon, C. Dubois, B. Gautier, J. C. Dupuy, E. Bustarret, L. Ortega, T. Klein, J. Boulmer, T. Kociniewski, and D. Débarre:
    Low-temperature transition to a superconducting phase in boron-doped silicon films grown on (001)-oriented silicon wafers
    Phys. Rev. B 81 (2010) 020501(R)
  3. E. Bustarett, C. Marcenat, P. Achatz, J. Kačmarčík, F. Lévy, A. Huxley, L. Ortéga, E. Bourgeois, X. Blase, D. Débarre, J. Boulmer:
    Superconductivity in doped cubic silicon,
    Nature 444, no. 7118 (2006) 465
  4. B. Sacépé, C. Chapelier, C. Marcenat, J. Kačmarčík, T. Klein, M. Bernard, E. Bustarett:
    Tunneling spectroscopy and vortex imaging in boron-doped diamond,
    Phys. Rev. Lett. 96 (2006) 097006-1-4
  1. G. Zhang, T. Samuely, N. Iwahara, J. Kačmarčík, Ch. Wang, P.W. May, J.K. Jochum, O. Onufriienko, P. Szabó, Sh. Zhou, P. Samuely, V.V. Moshchalkov, L.F. Chibotaru, H.G. Rubahn:
    Yu-Shiba-Rusinov bands in ferromagnetic superconducting diamond
    SCIENCE ADVANCES Vol. 6, no. 20, eaaz2536 (2020), DOI: 10.1126/sciadv.aaz2536
  2. G. Zhang, Y. Zhou, S. Korneychuk, T. Samuely, L. Liu, P. W. May, Z. Xu, O. Onufriienko, X. Zhang, J. Verbeeck, P. Samuely, V. V. Moshchalkov, Z. Yang, H.G. Rubahn:
    Superconductor-insulator transition driven by pressure-tuned intergrain coupling in nanodiamond films
    Phys. Rev. Materials 3, 034801, DOI:https://doi.org/10.1103/PhysRevMaterials.3.034801
  3. G. Zhang, T. Samuely, H. Du, Z. Xu, L. Liu, O. Onufriienko, P. W. May, J. Vanacken, P. Szabó, J. Kačmarčík, H. Yuan , P. Samuely, R. E. Dunin-Borkowski, J. Hofkens, and V. V. Moshchalkov:
    Bosonic Confinement and Coherence in Disordered Nanodiamond Arrays, ACS Nano 11 (2017), 11746, DOI: 10.1021/acsnano.7b07148.
  4. G. Zhang, T. Samuely, Z. Xu, J. K. Jochum, A. Volodin, S. Zhou, J. Vanacken, P. W. May, O. Onufriienko, J. Kacmarcík, J. A. Steele, J. Li, J. Vanacken, J. Vacík, P. Szabó, H. Yuan, M. B. J. Roeffaers, D. Cerbu, P. Samuely, J. Hofkens, V. V. Moshchalkov:
    Superconducting ferromagnetic nanodiamond,
    ACS Nano 11 (2017), 5358, DOI: 10.1021/acsnano.7b01688
  5. G. Zhang,T. Samuely, J. Kačmarčík, E.A. Ekimov, J. Li, J. Vanacken, P. Szabó, J. Huang, P.J. Pereira, D. Cerbu, and V.V. Moshchalkov:
    Bosonic Anomalies in Boron-Doped Polycrystalline Diamond,
    Phys. Rev. App. 6, 064011 (2016)
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