<html><body><div style="font-family: arial,helvetica,sans-serif; font-size: 12pt; color: #000000"><div style="color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><div style="font-family: times new roman, new york, times, serif; font-size: 12pt; color: #000000"><div style="text-align: center;"><img src="cid:97f3d2e403070df7b33ace4584ae47c99fd4fa05@zimbra"></div><div style="text-align: center;"><p style="margin: 0px; text-align: center;" align="center"><b><span style="font-family: 'Century Gothic','sans-serif'; color: #5f5f5f;" lang="EN-GB">Institut za fiziku, Bijenička cesta 46,</span></b></p><p style="margin: 0px; text-align: center;" align="center"><b><span style="font-family: 'Century Gothic','sans-serif'; color: #5f5f5f;" lang="EN-GB">predavaonica u zgradi Mladen Paić</span></b></p><b><span style="font-size: 14.0pt; font-family: 'Century Gothic','sans-serif'; color: #993300;" lang="EN-GB">četvrtak, 18. rujna 2014., u 15:00 sati</span></b></div><div style="text-align: center;"><b><br></b></div><div style="text-align: center;"><b><b><span style="font-size: 16.0pt; font-family: 'Times New Roman','serif'; color: #55913c;" lang="EN-GB"><br></span></b></b></div><div style="text-align: center;"><b><b><span style="font-size: 16.0pt; font-family: 'Times New Roman','serif'; color: #55913c;" lang="EN-GB">FINGERPRINTS OF HOPPING CONDUCTIVITY IN DISORDERED CHARGE DENSITY WAVE SYSTEMS</span></b></b></div><div style="text-align: center;"></div><div style="text-align: center;"><b><span style="font-size: 14.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB"><br></span></b></div><div style="text-align: center;"><b><span style="font-size: 14.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB">Dr. </span><span style="font-size: 14.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB">Damir Dominko</span><span style="font-size: 14.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB"></span></b><br></div><div><br></div><div style="text-align: center;"><p style="margin: 0px; text-align: center;" align="center"><b><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB">Institut za fiziku, Zagreb</span></b><b><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-US"></span></b></p><b><i><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB">E-mail: <a href="mailto:ddominko@ifs.hr" target="_blank">ddominko@ifs.hr</a></span></i></b><br data-mce-bogus="1"></div><div style="text-align: center;"><b><i><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB"><br></span></i></b></div><div style="text-align: left;"><b><b><i><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB"></span></i></b></b><p style="text-align: justify; margin: 0px;"><b><span style="font-size: 12.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB">Electric conductivity of charge density wave (CDW) systems exhibits rich variety of behavior; thermal activation across the gap at low fields below transition temperature T<sub>P</sub>, collective contribution (nonlinear conductivity channel) above the threshold field (E<sub>T</sub>) and variable range hopping (VRH) at low temperatures<sup>1</sup> and in granulated thin films in the whole temperature range<sup>2</sup>. Particularly the origin of the hopping conductivity is still unclear.</span></b></p><b><b><i><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB"></span></i></b></b><p style="margin: 0px; line-height: 115%;"><b><span style="font-family: 'Century Gothic','sans-serif';" lang="EN-GB">We have investigated the influence of disorder on conductivity phenomena in CDW systems TaS<sub>3</sub> and blue bronze (BB: K<sub>0.3</sub>MoO<sub>3</sub>) in a wide range of temperatures and electric fields using both the DC and pulse measurements at low and high fields respectively. Disorder has been introduced in several ways: (1) synthesis of TaS<sub>3</sub> samples doped with Nb, (2) irradiation of nominally pure TaS<sub>3</sub> samples and (3) deposition of granular thin BB films by pulsed laser deposition (PLD).</span></b></p><p style="margin: 0px; line-height: 115%;"><b><span style="font-family: 'Century Gothic','sans-serif';" lang="EN-GB"><br></span></b></p><p style="margin: 0px; line-height: 115%;"><b><span style="font-family: 'Century Gothic','sans-serif';" lang="EN-GB">Our results show that the nonlinear conductivity can be described by VRH already below 50 K in contrast to the linear channel, where it appears only below 20 K<sup>1</sup>. Moreover, the point defects in TaS3 introduced by doping and irradiation have no effect on VRH behavior. Together with the dielectric data, we will reevaluate microscopic picture of soliton hopping in CDW at low temperatures<sup>1,2,3</sup>. In granular thin BB films, on the other hand, the influence of grain boundaries is overwhelming even above T<sub>P</sub>, which is in contrast to the previous experiments on thin BB films<sup>5</sup>. The results can be understood by applying recent theoretical results for Beloborodov's Efros-Shlovskii VRH in granular materials<sup>6</sup>.</span></b></p><p style="margin: 0px; line-height: 115%;"><b><span style="font-family: 'Century Gothic','sans-serif';" lang="EN-GB"><br></span></b></p><b><b><i><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB"></span></i></b></b><p style="margin: 0px;"><b><span style="font-size: 10pt; font-family: 'Century Gothic', sans-serif;" lang="EN-GB">[1] M. E. Itkis, F. Ya. Nad, and P. Monceau, J. Phys. Cond. Matt. 2 (1990) 8327 </span></b></p><b><b><i><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB"></span></i></b></b><p style="margin: 0px;"><b><span style="font-size: 10pt; font-family: 'Century Gothic', sans-serif;" lang="EN-GB">[2] M. Đekić et al, Vacuum 98 (2013) 93-99</span></b></p><b><b><i><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB"></span></i></b></b><p style="margin: 0px;"><b><span style="font-size: 10pt; font-family: 'Century Gothic', sans-serif;" lang="EN-GB">[3] W. F. Pasveer, P. A. Bobbert, and M. A. J. Michels, Phys. Rev. B 74 (2006) 165209</span></b></p><b><b><i><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB"></span></i></b></b><p style="margin: 0px;"><b><span style="font-size: 10pt; font-family: 'Century Gothic', sans-serif;" lang="EN-GB">[4] A. S. Rodin and M. M. Fogler, Phys. Rev. B 80 (2009) 155435</span></b></p><b><b><i><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB"></span></i></b></b><p style="margin: 0px;"><b><span style="font-size: 10pt; font-family: 'Century Gothic', sans-serif;" lang="EN-GB">[5] O. C. Mantel, C. A. W. Bal, C. Langezaal, C. Dekker and H. S. J. Van Der Zant, J. App. Phys. 86, 4440 (1999)</span></b></p><b><i><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB"><b><span style="font-size: 10pt; font-family: 'Century Gothic', sans-serif;" lang="EN-GB">[6] I. Beloborodov, A. Lopatin, V. Vinokur, and K. B. Efetov, Rev. Mod. Phys. 79 (</span><span style="font-size: 10pt; font-family: 'Century Gothic', sans-serif;" lang="EN-GB">2007) 469-518</span></b><br></span></i></b></div><div><br></div><div><p style="margin: 0px; text-align: right;"><b><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';" lang="EN-GB">Voditelji seminara IF-a: Nikša Krstulović i Osor Bari</span></b><b><span style="font-size: 11.0pt; font-family: 'Century Gothic','sans-serif';">šić</span></b></p></div></div></div></div></body></html>