Dr. Richard Klemm

Richard KlemmProfessor of Physics

Dr. Richard Klemm, Ph.D., has been honored by the International Association of Who’s Who with the Albert Einstein Award of Physics for his achievements & the role of Physics Educator, at University of Central Florida.

Richard Klemm has worked in many fields of condensed matter physics. He began his scientific career as a synthetic organic chemist, working during the summers while an undergraduate in his father’s lab at the University of Oregon. Then, while an undergrad at Stanford, he worked with Fritz Schaefer and Frank Harris on atomic hyperfine structure calculations.

After graduating, he worked as a Research Technician at Synvar Research Institute in Palo Alto under the supervision of Fred Gamble. During that year, he was making transition metal dichalcogenides, in the hope of making interesting layered superconductors, and while Gamble was in Hawaii for a conference, Klemm found two interesting papers, one on the intercalation of TiS2 with long-chain organic amides, the other on the intercalation of graphite by FeCl3, and its subsequent reduction to make iron graphite. When Gamble returned, Klemm told him of his idea to try intercalation of a superconducting dichalcogenide. Although 2H-TaS2 only had a Tc value of 0.6o K, he thought to try intercalating it with pyridine, a stable ring compound. He then sealed off a glass tube with 2H-TaS2 immersed in pyridine, and heated it to 200o C, and the TaS2 grew in size visibly. Then Frank DiSalvo, then a graduate student of Ted Geballe at Stanford, measured it, and found it to be superconducting at 3.4o K, and the normal state resistivity was a anisotropic as in any of the high Tc superconductors discovered more than 18 years later.

After this discovery, Klemm went to Harvard, and wrote his doctoral thesis on Layered Superconductors, which included calculations of the upper critical field both parallel and perpendicular to the layers, and of the fluctuation diamagnetism and conductivity.

After graduate school, Klemm worked on the theory of quasi-one-dimensional conductors, using the bosonization technique pioneered by his thesis advisor, Alan Luther, and with Vic Emery. He also collaborated on renormalization group calculations on coupled one-dimensional conductors with Patrick Lee and Maurice Rice at Bell Labs, and studied the two-chain model for TTF-TCNQ with a particle-like and a hole-like chain in the same compound. Then, in collaboration with John Hertz (U. Chicago), he studied the dynamics of spin glasses while at Iowa State. While at ISU and at Exxon, he worked with Kurt Scharnberg (Hamburg) on heavion fermion superconductors, which were thought by some to be potential p-wave superconductors. Twenty years later, the Scharnberg-Klemm theory of the upper critical field of p-wave superconductors with broken symmetry was found by Hardy and Huxley to fit the temperature dependence of the upper critical field of URhGe in all three axis directions.

Presently, he is working with four graduate students, the “p-wave group” and the “Beijing p-wave group”, shown at the top of this webpage in the Fall of 2012 and in June of 2013. Loerscher and Zhang have used the Klemm-Clem transformations to incorporate single-electron effective mass anisotropy into the expressions for the upper critical field at an arbitrary field direction. This they are using to make further predictions for the angular dependence of the upper critical field for the polar state with completely broken symmetry, as in URhGe, and for the SK and/or ABM states possibly relevant for Sr2RuO4, thought by many to be a chiral p-wave state with order parameters A(px+ipy) and B(px-ipy), which would be in the non-chiral polar state with completely broken symmetry obtained from |A|=|B| at and just below the upper critical field for the field parallel to the layers, and in the chiral SK state with a non-equal mix of |A| and |B| for the field perpendicular to the layers. These fits will require the inclusion of Pauli pairbreaking, never before calculated for an antiparallel-spin pair state of any p-wave pairing orbital symmetry, as the recent measurements of the upper critical field parallel to the layers by Deguchi et al. and by Kittaka et al. show dramatic Pauli limiting effects. This Pauli limiting was first noted by Machida and Ichioka, and was discussed further in Layered Superconductors Volume 1. Although many workers had favored the O, Ru, and Sr Knight shift measurement results in Sr2RuO4, all of which seemed to favor a parallel-spin state for fields both parallel and normal to the layers, such measurements are indirect probes of the superconducting Cooper pairs, as they directly probe the nuclear spins, which only interact directly with the local atomic s-orbitals, and hence the interactions with the conduction electrons and/or the Cooper pairs, is at best a third-order effect. Such measurements can be affected by the presence of normal Ru inclusions, known to occur in that material, and by magnetic vortices since strong magnetic fields are necessary to perform most Knight shift measurements, whereas the upper critical field is a direct (and can be thermodynamic) measurement of the destruction of the superconducting Cooper pairs. Bianca Hall is studying these and other examples of the failure of Knight shift measurements. Loerscher and Zhang will also model the temperature and angular dependence of Hc2 in UCoGe, which has a complicated ferrimagnetic structure in the presence of the magnetic field, and the possibility of magnetic Fermi surface breakdown effects (such as a Lifshitz transition), using an ellipsoidal Fermi surface model. Hall, who recently became an official doctoral student at UCF, is also interested in the critical fields of (superconducting) doped topological insulators such as CuxBi2Se3, which has an Hc2 not inconsistent with a p-wave polar state for fields both parallel and normal to the layers, as shown in a PRL in 2012 by Bay et al. This might indicate that the orbital symmetry of the superconducting order parameter arose from an isotropic p-wave pairing interaction, as predicted by Scharnberg and Klemm in PRB in 1980. Why this would happen in a layered superconductor is presently a mystery in need of detailed study. Zhao, the newest member of the p-wave group, is working on microscopic models of parallel-spin pairing, such as the Appel-Fay model of ferromagnetic spin fluctuations.

Most recently, Klemm has been collaborating with Prof. Kazuo Kadowaki at the University of Tsukuba, Japan. They are working on the angular dependence of the coherent terahertz radiation emitted from mesas of Bi2212, which act as stacks of Josephson junctions.

 

Klemm, R. (n.d.). Richard Klemm Condensed Matter Theory. https://physics.ucf.edu/~klemm/