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- Bauch, Thilo, 1972, et al.
(författare)
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YBCOSQUIDs with unconventional current phase relation
- 2007
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Ingår i: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534. ; 463-465:1 October 2007, s. 979-984
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the dynamics of YBa2Cu3O7-delta,5 (YBCO) dc sperconducting quantum interference devices (SQUIDs) characterized by an unconventional Josephson current phase relation (CPR). We have focused on SQUID configurations with Josephson junctions where the lobe of the order parameter in one electrode is facing a node in the other electrode. This order parameter arrangement should enhance the appearance of a sin(2(p) term in the CPR. The response of the critical current of the dc SQUID, under the effect of an external magnetic field, has been measured in temperature, down to 20 mK. Our experimental data have been compared with numerical simulations of the SQUIDs dynamics by considering a CPR of a single junction of the form I(phi) = I-I sin(phi) - I-II sin(2 phi) where I-I, and I-II are, respectively, the first and second harmonic component. In our devices the values of the sin(2 phi) term are such that the fundamental state of the SQUID is naturally double degenerate. This is of great relevance for applications of d-wave SQUIDs in quantum information processing. (C) 2007 Elsevier B.V. All rights reserved.
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- Hübinette, Tobias
(författare)
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Comforting an orphaned nation : Representations of international adoption and adopted Koreans in Korean popular culture
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This is a study of popular cultural representations of international adoption and adopted Koreans in Western countries. The study is carried out from a postcolonial perspective and uses a cultural studies reading of four feature films and four popular songs as primary sources. The aim is to examine how nationalism is articulated in various ways in light of the colonial experiences in modern Korean history and recent postcolonial developments within contemporary Korean society. The principal question addressed is: What are the implications for a nation depicting itself as one extended family and which has sent away so many of its own children, and what are the reactions from a culture emphasising homogeneity when encountering and dealing with the adopted Koreans? After an introductory chapter, Chapter 2 gives the history of international adoption from Korea, and Chapter 3 is an account of the development of the adoption issue in the political discussion. Chapters 4, 5, 6 and 7 analyse the cinematic and lyrical representations of adopted Koreans in four feature films and popular songs respectively. Chapter 4 considers the gendering of the colonised nation and the maternalisation of roots, drawing on theories of nationalism as a gendered discourse. Chapter 5 examines the issue of hybridity and the relationship between Koreanness and Whiteness, which are related to the notions of third space, mimicry and passing. Linked to studies of national division, reunification and family separation, Chapter 6 looks at the adopted Koreans as symbols of a fractured and fragmented nation. Chapter 7 focuses on the emergence of a global Korean community, with regards to theories of globalisation, diasporas and transnationalism. In the concluding chapter, the study argues that the Korean adoption issue can be conceptualised as an attempt at overcoming a difficult past and imagining a common future for all ethnic Koreans at a transnational level.
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- Lindström, Tobias, 1976
(författare)
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d-wave Josephson Junctions
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The properties of d-wave YBCO Josephson junctions and dc-SQUIDs with high misorientation angles have beenstudied experimentally .The predominant d-wave symmetry of the pairing wavefunction in high-Tc superconductors has, to a large extent, beena hinderance in applications, but it also makes it possible to fabricate devices with novel properties that may be suitablefor applications in the quantum regime; one particulary interesting property is a strong second harmonic component in the current-phase relation ofjunctions with the electrodes oriented in a node-lobe arrangement; so-called 0-45 junctions.The work has been focused on the properties of grain-boundary 0-45 dc-SQUIDs: Their dc-properties as wellas the effects of a strong second harmonic component on the dynamics have been studied experimentally andmodelled numerically. The experimental results can be explained by taking into account the meandering ofthe grain boundary which in combination with a strong orientational dependence of the transport properties due to thed-wave symmetry results in interfaces with properties that change dramatically over a length scale of 50-100 nm.The properties of grain-boundary YBCO 0-45 junctions have been studied in the quantum regime. Macroscopicquantum tunnelling has been demonstrated in these junctions and microwave spectroscopy is here used to verifythe presence of discrete energy levels. The quality factor of the junction has been experimentally determined to 40+-10, a much higher value than previously believed to be possible in high-Tc structures.Finally, the possibility of using high-T$_c$ structures to build qubits is discussed. There is now a renewedinterest in this possibility, especially in light of our recent results whichdemonstrate that the inherent dissipation mechanisms are much less detrimental to coherent phenomena than previously feared.
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- Lombardi, Floriana, 1967, et al.
(författare)
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Quantum properties of d-wave YBa2Cu3O7-δ Josephson junction
- 2006
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Ingår i: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534. ; 435:1-2, s. 8-11
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the transport properties of YBa2Cu3O7-δ (YBCO) dc SQUIDs with Josephson junctions characterized by a combination of 45° [0 0 1] tilt and α [1 0 0] tilt grain boundary with α = 0°, ±10° and 45°. By increasing the component of transport in the YBCO c-axis direction (increasing values of α), the SQUIDs showed an enhanced quality factor. At the same time, for all the devices the response under an external magnetic field presented the main features of an unconventional Josephson current phase relation with a pronounced sin 2 component. Switching current measurements at low temperature (10th of mK) also revealed that the dynamics of grain boundary junction resulting from a combination of 45° [0 0 1] and 45° [1 0 0] tilt is dominated by macroscopic quantum tunnelling of the superconductive phase. The features are quite encouraging for applications of d-wave junctions in quantum circuitry.
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