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Josephson Vortices in Layered Nanostructures

#3162


Studies of Dynamics of Josephson Vortices in Layered Superconductors for Development of New Fast Operating Devices

Tech Area / Field

  • INF-ELE/Microelectronics and Optoelectronics/Information and Communications
  • PHY-RAW/Radiofrequency Waves/Physics
  • PHY-SSP/Solid State Physics/Physics

Status
3 Approved without Funding

Registration date
29.11.2004

Leading Institute
Russian Academy of Sciences / Institute of Radioengineering and Electronics, Russia, Moscow

Collaborators

  • Los Alamos National Laboratory / Theoretical Division, Group T11, USA, NM, Los-Alamos\nArgonne National Laboratory (ANL), USA, IL, Argonne\nNational Institute for Materials Science, Japan, Tsukuba

Project summary

The layered crystalline structure of the most anisotropic high temperature superconductors (HTS) such as Bi2Sr2CaCu2O8+x represents a vertical tunnel structure where elementary superconducting layers (CuO2) are separated by atomically thin (BiO+SrO) insulating layers. That naturally layered tunnel nanostructure is in many aspects a unique system for studies of the Josephson effects at atomic scale (so called Intrinsic Josephson effects (IJE) [1]). Elementary Josephson junctions have a nanometer scale size (1.5 nm for BI-2212) along the c-axis. The perspective of using these junctions as the base elements opens a way for a development of an electronics of new generation – superconducting nano-electronics. Last decade those layered nano-structures attract increasing interest [1-13].

For observation of oscillatory dependence of the critical current on magnetic field typical for the DC IJE the lateral sizes of the structure L should be less then Josephson penetration depth lJ, which is about 1 mm in Bi-2212. Those structures have been recently fabricated [4] and used for successful demonstration of IJE [6] with the assistance of the authors of the present project. At the opposite limit of “long” structure L >> lJ the Josephson vortices can enter into the structure under magnetic field parallel to the layers. Josephson vortices are centered at the insulating layers and thus have no normal cores. Therefore, they can move very fast along the layers while being driven by Lorentz force induced by steady current across the layers. At high current limit they can reach high velocities corresponding to emission of electromagnetic waves in THz frequency range.

With field increase vortex concentration increases and repulsive interaction between them leads to formation of triangular Josephson vortex lattice (JVL). At high enough field Josephson vortices fill every elementary junction forming dense JVL. The intervortex interaction in that case is so strong that a driven lattice can move as a whole. That collective regime of JVL motion often referred to as Josephson flux-flow (JFF) is of the most interest since it should be accompanied by coherent Josephson emission. This regime can be identified as a collective branch on the current voltage (I-V) characteristic where the voltage is proportional to the lattice velocity and to the linear vortex density proportional to magnetic field. The maximum voltage of collective branch corresponds to the lattice motion with Swihart velocity. Coherent JFF emission is the most attractive JFF property for high frequency applications. A frequency of JFF emission is proportional to the lattice period, i.e. to magnetic field. So the frequency can reach 1-2 THz at fields of ~ 2T and also can be tuned by bias current controlling the lattice velocity. The power of JFF emission should depend on the number of synchronized elementary junctions and for highly coherent JFF regime that can exceed by several orders the emission intensity from usual Josephson junctions.

Investigation of conditions for realization of JFF emission on HTS stacked structures in subTHz – THz frequency region is one of the main goals of this project. Until recently these studies are still in the beginning stage. The JFF branch has been identified at the I-V characteristics of long stacked structures at parallel magnetic field with JFF voltage being proportional to the field value [2]. The first observation of coherent JFF response to external microwaves at frequency range 50-150 GHz has been recently demonstrated [7].

In the course of this project we will study dissipative, coherent and high frequency properties of highly mobile JVL. We will study the possibility of high-speed manipulation with JFF by perpendicular component of magnetic field (magnetic gate type effects) and by injection currents. The capability of synchronization of a vast number of intrinsic junctions (up to several thousands) to provide coherent JFF emission of high intensity will be studied. The mechanisms of high frequency limitation of JFF emission will be investigated as well. We will study the effects of the commensurability of the JVL period with dimensions of the stacked structure and the effect of conversion of triangular type lattice into more “fast” rectangular type on short stacks. The effect of interaction of two moving vortex lattices separated by small distance will be also investigated. To extend the possible frequency range of JFF emission we will study JFF behavior in a variety of others, different from Bi-2212, layered HTS materials including magneto-oxide superconductors.

Another possibility for the realization of THz emission in layered nanostructures is related with coherent nature of interlayer tunneling in layered conductors. Theoretical studies carried out by the authors of the project pointed out that coherent interlayer tunneling can result in the regime of negative differential conductance on tunneling I-V characteristics [13]. Experimentally, significant contribution of coherent interlayer tunneling in layered conductors and superconductors has been recently demonstrated [5, 11]. We are going to undertake searching for this regime and for the instability of stationary state related. We will study the capability of using the negative differential conductance regime for generation and detection of microwaves in THz frequency range. Theoretically, the high frequency limit of the AC currents generated in that case should be determined by momentum relaxation rate of electrons.

Participants of the project have much experience in growth of high quality single crystals of the layered high temperature superconductors [3], in micro-fabrication of the stacked structures using lithography and focused ion beam techniques [4] and in investigation of their transport properties [1-13]. The authors have got a number of new results in studies of interlayer tunneling in layered high temperature superconductors. Particularly, they demonstrated DC and AC intrinsic Josephson effects on micron sized Bi-2212 stacked structures [6, 8, 9], specified the properties of interlayer tunneling in Bi-2212 related to its coherent nature and to the d-wave symmetry of the order parameter [5]. It was shown that the main contribution to the JFF dissipation in wide temperature range comes from the in-plane AC quasiparticle currents. The authors developed a new independent method for studies of the in-plane and out-of-plane components of quasiparticle conductivity in layered superconductors based on the measurements of losses in the JFF regime [10], they found effect of renormalization of Swihart velocity in non-linear JFF regime when Josephson oscillation frequency exceeds quasiparticle relaxation rate [10]. The authors carried out the first experiments on demonstration of longitudinal and transversal coherency of JFF [7]. Theoretically, the stability of moving Josephson vortex lattices has been studied and it was shown that only triangular type of moving JVL is stable [12].

During the process of these studies a fruitful international cooperation has been established with such Japanese and American scientific centers as Tohoku University (Sendai), University of Tokyo, National Institute for Material Science (Tsukuba), Los Alamos National Laboratory, Argonne national Laboratory. That resulted in a number of joint publications [4-11]. We suppose to continue this cooperation in the frame of present project. Another merit of this project is that it joints and balances technological, experimental and theoretical components of the investigation.

The interlayer tunneling is the subject of intensive studying in many leading scientific centers: there are several big projects in Japan, Germany and United States (theoretical).

Present project as a whole and in its separate parts is quite consistent with the purposes of ISTC. The project provides a possibility for a group of scientists from IRE having knowledge and qualification for development of military equipment to reorient their activity completely to peaceful scientific researches, and to exclude from their scientific plans the contracts connected with military research applications that compensate the lack of financial support for basic researches in IRE.

References:

1. Yu.I. Latyshev, J.E. Nevelskaya and P. Monceau, "Dimensional crossover for intrinsic dc Josephson effect in Bi2Sr2CaCu2Ox 2212 single crystal whiskers", Phys. Rev. Lett. 77 (1996) 932-935.

2. Yu.I. Latyshev, P.Monceau, and V.N. Pavlenko “Intrinsic Josephson effects on stacks fabricated from high quality BSCCO 2212 single crystal whiskers”, Physica C, 293 (1997) 174-180; ibid. 282-287 (1997) 387-390.

3. Yu.I. Latyshev, I.G. Gorlova, A.M. Nikitina, V.U. Antokhina, S.G. Zybtsev, N.P. Kukhta and V.N. Timofeev, "Growth and study of single-phase 2212 BSCCO whiskers of submicron cross sectional area", Physica C 216 (1993) 471-477.

4. Yu.I. Latyshev, S.-J. Kim, and T. Yamashita, “Fabrication of submicron BSCCO stacked junctions by focused ion beam (FIB)”, IEEE Trans. on Appl. Supercond., 9 (1999) 4312-4315; S.-J. Kim, Yu.I. Latyshev and T. Yamashita, “Submicron stacked-junction fabrication from Bi2Sr2CaCu2O8+x whiskers by focused-ion-beam etching”, Appl. Phys. Lett., 74 (1999) 1156-1158; S.-J. Kim, Yu. I. Latyshev, and T. Yamashita, «3D intrinsic Josephson junctions using c-axis thin films and single crystals». Supercond. Sci. Technol., 12 (1999) 729-731.

5. Yu.I. Latyshev, T. Yamashita, L.N. Bulaevskii, M.J. Graf, A.V. Balatsky, and M.P. Maley, “Interlayer transport of quasiparticles and Cooper pairs in Bi2Sr2CaCu2O8+x superconductors”, Phys. Rev. Lett., 82 (1999) 5345-5348.

6. Yu.I. Latyshev, S.-J. Kim, V.N. Pavlenko, T. Yamashita, and L.N. Bulaevskii, “Interlayer tunneling of quasiparticles and Cooper pairs in Bi-2212 from experiments on small stacks”, Physica C, 362 (2001) 156-163.

7. Yu.I. Latyshev, M.B. Gaifullin, T. Yamashita and Yuji Matsuda, “The c-axis coherent response of Bi-2212 Josephson flux-flow junction to mm-wave radiation”, Supercond. Sci. Technol. 14 (2001) 1018-1021.

8. Yu.I. Latyshev, M.B. Gaifullin, T. Yamashita, M. Machida, and Yuji Matsuda, “Shapiro Step Response in the Coherent Josephson Flux Flow State of Bi2Sr2CaCu2O8+x”, Phys. Rev. Lett., 87 (2001) 247007(4); M.B. Gaifullin, Yu.I. Latyshev, T. Yamashita, Yuji Matsuda, “Shapiro step response in Bi2Sr2CaCu2O8+x in parallel and tilted magnetic field”, Physica C, 392-396 (2003) 319-322.

9. Yu.I. Latyshev, A.E. Koshelev, V.N. Pavlenko, M.B. Gaifullin, T. Yamashita and Yuji Matsuda, “Novel features of Josephson flux-flow in Bi-2212: contribution of in-plane dissipation, coherent response to mm-wave radiation, size effect”, Physica C, 367 (2002) 365-375.

10. Yu.I. Latyshev, A.E. Koshelev, and L.N. Bulaevskii, “Probing quasiparticle dynamics in Bi2Sr2CaCu2O8+x with a driven Josephson vortex lattice”, Phys. Rev. B 68 (2003) 134504(10).

11. Yu.I. Latyshev, A.A. Sinchenko, L.N. Bulaevskii, V.N. Pavlenko, P. Monceau “Coherent tunneling between elementary conducting layers in charge density wave conductor NbSe3”, Pis’ma v ZhETF, 75 (2002) 103-108.

12. S.N. Artemenko and S.V. Remizov, “Stability of driven Josephson vortex lattice in layered superconductors revisited”, Phys. Rev. B 67 (2003) 144516(6).

13. S.N. Artemenko and A.F. Volkov, “N-type dependence of the transverse current on the voltage in layered crystals”, Sov. Phys. Sol. State, 23 (1981), 1257-1258; S.N. Artemenko and A.G. Kobelkov, “Intrinsic Josephson effect and violation of the Josephson relation in layered superconductors”, Phys. Rev. Lett., 78 (1997) 3551-3554.


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