The oxide superconductors, particularly those recently discovered that are based on La<sub>2</sub>CuO<sub>4</sub>, have a set of peculiarities that suggest a common, unique mechanism: they tend in every case to occur near a metal-insulator transition into an odd-electron insulator with peculiar magnetic properties. This insulating phase is proposed to be the long-sought "resonating-valence-bond" state or "quantum spin liquid" hypothesized in 1973. This insulating magnetic phase is favored by low spin, low dimensionality, and magnetic frustration. The preexisting magnetic singlet pairs of the insulating state become charged superconducting pairs when the insulator is doped sufficiently strongly.

Limited Time Offer

Premium members can get their quote collection automatically imported into their Quotewise collections.

By symmetry we mean the existence of different viewpoints from which the system appears the same. It is only slightly overstating the case to say that physics is the study of symmetry. The first demonstration of the power of this idea may have been by Newton, who may have asked himself the question: What if the matter here in my hand obeys the same laws as that up in the sky—that is, what if space and matter are homogeneous and isotropic?

I learned, practically in my cradle (actually from Bill McMillan's thesis), that the ground state wave function of a system of bosons should necessarily be real and positive, a fact which made his early Monte Carlo simulations infinitely easier.

My Harvard classmate, Thomas S. Kuhn wrote, some years ago, an influential book about scientific revolutions. Fortunately, many scientific revolutions do not follow his scenario, but the one he focused on, the discovery of quantum mechanics, is well described by his model, which is most valid for a revolution occurring in the central core of a mature science.

Share Your Favorite Quotes

Know a quote that's missing? Help grow our collection.

That Big Science culture in the USA, and similar groups elswhere, tended to have separate, direct access to government and hence to funding sources. It was independent to a great extent of the rest of science, of which it was never a majority component except in funding.

It is seen as the application of a systematic “scientific method” involving wearing a white coat and being dull. I feel that too many young people come into science with this view, and that too many fields degenerate into the kind of work which results: automatic crank-turning and data-collecting of the sort which Kuhn calls “normal science” and Rutherford “stamp-collecting”. In fact, the creation of new science is a creative act, literally, and people who are not creative are not very good at it.

The behavior of large and complex aggregates of elementary particles, it turns out, is not to be understood in terms of a simple extrapolation of a few particles. Instead, at each level of complexity entirely new properties appear, and the understanding of the new behaviors requires research which I think is as fundamental in its nature as any other.