Interlayer tunneling of quasiparticles and Cooper pairs in Bi-2212 from experiments on small stacks Yu.I. Latyshev a,b,c, * , S.-J. Kim a,c , V.N. Pavlenko a,b , T. Yamashita a,c , L.N. Bulaevskii d a Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan b Institute of Radio-Engineering and Electronics, Russian Academy of Sciences, 11-7 Mokhovaya street, GSP, Moscow 101999, Russia c CREST, Japan Science and Technology Corporation, Japan d Theory Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA Received 23 August 2000 Abstract The interlayer tunneling has been studied on high quality Bi-2212 stacks of micron to the submicron lateral size. We found that low temperature and low voltage tunneling I±V characteristics can be self-consistently described by Fermi- liquid model for a d-wave superconductor with a signi®cant contribution from coherent interlayer tunneling. For micron-sized stacks we found very clear Fraunhofer type dependence of critical current across the stack on parallel magnetic ®eld with periodicity corresponding to one ¯ux quantum per elementary junction. The gap and pseudogap interplay with variation of temperature and magnetic ®eld has been extracted from the I±V characteristics. We consider also the role of charging eects for submicron stacks. Ó 2001 Elsevier Science B.V. All rights reserved. PACS: 74.72.Hs; 74.50.r Keywords: Interlayer tunneling coherency; Gap symmetry; Pseudogap; Charging eects 1. Introduction The layered structure of the most aniso- tropic high-T c superconductors can be considered as a stack of the elementary Josephson junctions formed between superconducting double CuO 2 layers separated by isolating BiO 2 and SrO 2 layers. That provides possibility of studies the interlayer tunneling of quasiparticles [1] and Cooper pairs [2]. As it was pointed out in Ref [3], to observe intrinsic Josephson eects one needs to have stacks of very small in-plane size, compared or less than Josephson penetration depth k J sk c =k ab , where s is the spacing between superconducting layers and k c , k ab are anisotropic London penetration depths. The typical value of k J for high-T c materials of Bi- 2212 type is of the order of 1 lm. For the structure with bigger in-plane size the entering Josephson vortices can break phase coherency between the layers. Another request is a high crystallographic perfection of the structure, since defects and im- purities can also break interlayer phase coherence. Physica C 362 2001) 156±163 www.elsevier.com/locate/physc * Corresponding author. Address: Institute of Radio-Engi- neering and Electronics, Russian Academy of Sciences, 11 Mokhovaya street, 103907 Moscow, Russia. Tel.: +7-95-203- 4976; fax: +7-95-203-8414. E-mail address: lat@mail.cplire.ru Yu.I. Latyshev). 0921-4534/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0921-453401)00663-3