Electromagnetic Absorption in the Copper Oxide Superconductors
Electromagnetic Absorption in the Copper Oxide Superconductors

Author: Frank J. Owens

Publisher: Springer Science & Business Media

Published: 2006-04-11

Total Pages: 208

ISBN-13: 0306470829

DOWNLOAD EBOOK

In 1987 a major breakthrough occurred in materials science. A new family of materials was discovered that became superconducting above the temperature at which nitrogen gas liquifies, namely, 77 K or –196°C. Within months of the discovery, a wide variety of experimental techniques were brought to bear in order to measure the properties of these materials and to gain an understanding of why they superconduct at such high temperatures. Among the techniques used were electromagnetic absorption in both the normal and the superconducting states. The measurements enabled the determination of a wide variety of properties, and in some instances led to the observation of new effects not seen by other measu- ments, such as the existence of weak-link microwave absorption at low dc magnetic fields. The number of different properties and the degree of detail that can be obtained from magnetic field- and temperature-dependent studies of electromagnetic abso- tion are not widely appreciated. For example, these measurements can provide information on the band gap, critical fields, the H–T irreversibility line, the amount of trapped flux, and even information about the symmetry of the wave function of the Cooper pairs. It is possible to use low dc magnetic field-induced absorption of microwaves with derivative detection to verify the presence of superconductivity in a matter of minutes, and the measurements are often more straightforward than others. For example, they do not require the physical contact with the sample that is necessary when using four-probe resistivity to detect superconductivity.

Electromagnetic Absorption in the Copper Oxide Superconductors
Electromagnetic Absorption in the Copper Oxide Superconductors

Author: Frank J. Owens

Publisher: Springer

Published: 2013-03-22

Total Pages: 199

ISBN-13: 9781475787603

DOWNLOAD EBOOK

In 1987 a major breakthrough occurred in materials science. A new family of materials was discovered that became superconducting above the temperature at which nitrogen gas liquifies, namely, 77 K or –196°C. Within months of the discovery, a wide variety of experimental techniques were brought to bear in order to measure the properties of these materials and to gain an understanding of why they superconduct at such high temperatures. Among the techniques used were electromagnetic absorption in both the normal and the superconducting states. The measurements enabled the determination of a wide variety of properties, and in some instances led to the observation of new effects not seen by other measu- ments, such as the existence of weak-link microwave absorption at low dc magnetic fields. The number of different properties and the degree of detail that can be obtained from magnetic field- and temperature-dependent studies of electromagnetic abso- tion are not widely appreciated. For example, these measurements can provide information on the band gap, critical fields, the H–T irreversibility line, the amount of trapped flux, and even information about the symmetry of the wave function of the Cooper pairs. It is possible to use low dc magnetic field-induced absorption of microwaves with derivative detection to verify the presence of superconductivity in a matter of minutes, and the measurements are often more straightforward than others. For example, they do not require the physical contact with the sample that is necessary when using four-probe resistivity to detect superconductivity.

The Indomitable Chemist
The Indomitable Chemist

Author: Dr. Arvind Yadav

Publisher: Notion Press

Published: 2023-11-08

Total Pages: 346

ISBN-13:

DOWNLOAD EBOOK

Prof. CNR Rao is a living legend. Einstein paid a compliment to Mahatma Gandhi on his 70th birthday. He said, “Generations to come, it may well be, will scarce believe that such a man as this one ever in flesh and blood walked upon this earth”. On Prof. Rao’s birthday, I would repeat these words. Prof. Rao is not an individual, he is an institution, he is a phenomenon. I feel lucky that our generations could see him, touch him, feel him, experience him, learn from him and get inspired by him. I have watched Prof. Rao as a scientist, as a science leader, as a science institution builder and indeed as a leader of leaders of science. I have also watched him as a wonderful, warm-hearted human being with abundant empathy. I have seen his childlike enthusiasm. I have watched him as `courage personified’. What follows is more anecdotal but solely based on my personal viewpoint. Professor Rao has had a tremendous influence on my life. He has been my guru, guide, friend and philosopher. I met him for the first time when he was the Chairman of the Research Advisory Council of the National Chemical Laboratory (NCL) in the nineteen eighties. I was then in my late thirties. Professor Rao has an uncanny ability to spot talent among the young. He was the President of the Indian Science Congress in the year 1988, which was held in Pune University. Mr. Rajiv Gandhi was the Prime Minister and he inaugurated the Science Congress. Later on, during the lunch that followed, Prof. Rao made a special point to introduce me to Rajiv Gandhi. I still remember his words. He said, `Mr. Prime Minister, meet a rising young star of Indian science’. Little did I then know that within the next couple of months, he would make me a member of the Science Advisory Council to the Prime Minister, which he was chairing. At 42, I was the youngest member and I remember people calling me the `baby’ of the team. Getting that huge exposure at such a young age was something very special for me – I got a helicopter view of India at large. It helped me enormously as I moved on in life. 'Padma Vibhushan' Dr. Raghunath Anant Mashelkar

Microwave Studies of High Tc Copper Oxide Superconductors and NbN
Microwave Studies of High Tc Copper Oxide Superconductors and NbN

Author: Chi-Chung Chin

Publisher:

Published: 1991

Total Pages: 96

ISBN-13:

DOWNLOAD EBOOK

This report covers several projects, namely: surface impedance measurements using both stripline and cavity resonators; microwave magnetic field dependence measurements of the surface impedance of NbN; determination of the upper critical field of YBa2Cu3O7 by microwave measurements; and the calculation of the angular dependence of an anisotropic superconductor. The temperature and frequency dependencies of the surface impedance of NbN thin films were measured using a stripline resonator from 4.2 to 13 K and from 0.5 to 10 GHz. At 4.2 K resonant cavity measurements of the surface resistance were made at 35 and 56 GHz. From the surface reactance measurements using both cavity and stripline techniques, we obtain the penetration depth extrapolated to T=0 K. Lamba(0)=3700A. For the stripline, the film thickness was approximately 8000 angstrom, which is about twice the measured penetration depth. The weak-coupling (full) Mattis-Bardeen theory appropriate for NbN was used to fit the temperature dependence on the surface resistance. Based on the quality of the weak-coupling fit to the data, we conclude that the strong-coupling effect is not important in the local and dirty limits. The correction of the stripline measurements of the surface resistance due to the finite film thickness is discussed.