Biomedical subjects

J Schmalian

Publications and source records attributed to J Schmalian.

14 recordsLinked to original sources

PubMed2006

Quantum critical end point for the Kondo volume collapse model.

The Kondo volume collapse describes valence transitions in f-electron metals and is characterized by a line of first order transitions in the pressure-temperature phase plane terminated at critical end points. We analyze the quantum critical end point, when the lower end point is tuned to T=0, and determine the specific heat, thermal expansion, and compressibility. We find that the inclusion of quantum critical fluctuations leads to a novel bifurcation of the first order phase line. Finally, we show that critical strain fluctuations can cause both, superconductivity and non-Fermi liquid behavior near the critical point.

Journal Article↗

PubMed2005

Dynamics of magnetic defects in heavy fermion LiV2O4 from stretched exponential 7Li NMR relaxation.

7Li NMR measurements on LiV2O4 from 0.5 to 4.2 K are reported. A small concentration of magnetic defects within the structure drastically changes the nuclear magnetization relaxation versus time from a pure exponential as in pure LiV2O4 to a stretched exponential, indicating glassy behavior of the magnetic defects. The stretched exponential function is described as arising from a distribution of 7Li nuclear spin-lattice relaxation rates and we present a model for the distribution in terms of the dynamics of the magnetic defects. Our results explain the origin of recent puzzling 7Li NMR literature data on LiV2O4 and our model is likely applicable to other glassy systems.

Journal Article↗

PubMed2003

"Devil's staircase" in Pb/Si(111) ordered phases.

With scanning tunneling microscopy we have found that ordered phases in Pb/Si(111) are one of the best examples of the "devil's staircase" phase diagram. Phases within a narrow coverage range (1.2<theta<1.3 monolayers) are constructed with the rules similar to the ones found in theoretical models.

Journal Article↗

PubMed2002

Neutron resonance in the cuprates and its effect on fermionic excitations.

We argue that the exciton scenario for the magnetic resonance in the cuprate superconductors yields a small spectral weight of the resonance, in agreement with experiment. We show that the small weight is related to its concentration in a small region of momentum and energy. Despite this, we find that a large fermionic self-energy can indeed be generated by a resonance with such properties, i.e., the scattering from the resonance substantially affects the electronic properties of the cuprates below T(c).

Journal Article↗

PubMed2001

Local defect in metallic quantum critical systems.

We present a theory of a single point, line, or plane defect coupling to the square of the order parameter in a metallic system near a quantum critical point at or above its upper critical dimension. At criticality, a spin droplet is nucleated around the defect with its core size determined by the strength of the defect potential. Outside the core a universal slowly decaying tail of the droplet is found, leading to many dissipative channels coupling to the droplet and to a complete suppression of quantum tunneling. We propose an NMR experiment to measure the impurity-induced changes in the local spin susceptibility.

Journal Article↗

PubMed2000

Quantification of magnetic domain disorder and correlations in antiferromagnetically coupled multilayers by neutron reflectometry

The in-plane correlation lengths and angular dispersion of magnetic domains in a transition metal multilayer have been studied using off-specular neutron reflectometry techniques. A theoretical framework considering both structural and magnetic disorder has been developed, quantitatively connecting the observed scattering to the in-plane correlation length and the dispersion of the local magnetization vector about the mean macroscopic direction. The antiferromagnetic domain structure is highly vertically correlated throughout the multilayer. We are easily able to relate the neutron determined magnetic domain dispersion to magnetization and magnetoresistance experiments.

Journal Article↗

PubMed2000

Stripe glasses: self-generated randomness in a uniformly frustrated system

We show that a system with competing interactions on different length scales, relevant to the formation of stripes in doped Mott insulators, undergoes a self-generated glass transition which is caused by the frustrated nature of the interactions and not related to the presence of quenched disorder. An exponentially large number of metastable configurations is found, leading to a slow, landscape dominated long time relaxation and a breakup of the system into a disordered inhomogeneous state.

Journal Article↗

PubMed2000

The middle way.

Mesoscopic organization in soft, hard, and biological matter is examined in the context of our present understanding of the principles responsible for emergent organized behavior (crystallinity, ferromagnetism, superconductivity, etc.) at long wavelengths in very large aggregations of particles. Particular attention is paid to the possibility that as-yet-undiscovered organizing principles might be at work at the mesoscopic scale, intermediate between atomic and macroscopic dimensions, and the implications of their discovery for biology and the physical sciences. The search for the existence and universality of such rules, the proof or disproof of organizing principles appropriate to the mesoscopic domain, is called the middle way.

Macromolecular Substances↗

PubMed1996