Insulating Josephson Junction Chains as Pinned Luttinger Liquids

Abstract

Quantum physics in one spatial dimension is remarkably rich, yet even with\nstrong interactions and disorder, surprisingly tractable. This is due to the\nfact that the low-energy physics of nearly all one-dimensional systems can be\ncast in terms of the Luttinger liquid, a key concept that parallels that of the\nFermi liquid in higher dimensions. Although there have been many theoretical\nproposals to use linear chains and ladders of Josephson junctions to create\nnovel quantum phases and devices, only modest progress has been made\nexperimentally. One major roadblock has been understanding the role of disorder\nin such systems. We present experimental results that establish the insulating\nstate of linear chains of sub-micron Josephson junctions as Luttinger liquids\npinned by random offset charges, providing a one-dimensional implementation of\nthe Bose glass, strongly validating the quantum many-body theory of\none-dimensional disordered systems. The ubiquity of such an electronic glass in\nJosephson-junction chains has important implications for their proposed use as\na fundamental current standard, which is based on synchronisation of coherent\ntunnelling of flux quanta (quantum phase slips).\n