Orbital-order phase transition in Pr1−xCaxMnO3 probed by photovoltaics

Ultrafast structural phase transition driven by photoinduced melting of charge and orbital order.

We use femtosecond x-ray diffraction to probe directly the structural dynamics of a charge ordered and orbitally ordered thin film of La0.42Ca0.58MnO3 initiated by an ultrafast optical pulse. At low excitation fluences we observe the displacive excitation of a coherent optical A(g) phonon. Under high excitation conditions we observe a complete phase transition within 1 ps via the disappearance ...

Orbital phase transition in 2-d pyrochlore

We present here correlation driven orbital Mott transition in 2 dimensional pyrochlore lattice. We study a model Hamiltonian in which we take Hund’s coupling between itinerant and localized electrons apart from the coulomb interaction. In the weak coupling limit, we calculate zero temperature susceptibility under random phase approximation and find the model in para orbital phase. In strong cou...

Ultrafast electronic phase transition in La1/2Sr3/2MnO4 by coherent vibrational excitation: evidence for nonthermal melting of orbital order.

An ultrafast electronic phase transition, associated with melting of orbital order, is driven in La1/2Sr3/2MnO4 by selectively exciting the Mn-O stretching mode with femtosecond pulses at 16 microm wavelength. The energy coupled into this vibration is less than 1% of that necessary to induce the transition thermally. Nonthermal melting of this electronic phase originates from coherent lattice d...

Order of superconductive phase transition

On the occasion of Reinhard Folk's 60th birthday, I give a brief review of the theoretical progress in understanding the critical properties of super-conductors. I point out the theoretical difficulties in finding a second-order transition in the Ginzburg-Landau Model with O(N)-symmetry in 4 − ε Dimensions , and the success in predicting the existence and location of a tricritical point with th...

Explorer Metal - Insulator Transition and Orbital Order in PbRuO 3