Hidden states of matter may be created if a system out of equilibrium follows a trajectory to a state that is inaccessible or does not exist under normal equilibrium conditions. We found such a hidden (H) electronic state in a layered dichalcogenide crystal of 1TTaS2 (the trigonal phase of tantalum disulfide) reached as a result of a quench caused by a single 35femtosecond laser pulse. In comparison to other states of the system, the H state exhibits a large drop of electrical resistance, strongly modified singleparticle and collectivemode spectra, and a marked change of optical reflectivity. The H state is stable until a laser pulse, electrical current, or thermal erase procedure is applied, causing it to revert to the thermodynamic ground state.
COBISS.SI-ID: 27627303
We demonstrate a new and effective method of producing singlephase superconducting δ3MoN nanowires from bundled Mo6SyIz (8.2 ≤ y + z ≤10) nanowire templates in the presence of ammonia gas. Magnetic susceptibility and electrical resistance measurements confirm singlephase material synthesis. Measurements of fourcontact resistance on single wires with diameters above 100 nm in a magnetic field are used to determine the critical field, while diameter dependence and magnetization measurements are used to investigate the homogeneity of the nanowires.
COBISS.SI-ID: 27331623
The study of the temporal evolution of systems undergoing symmetry breaking phase transitions—whether it is in condensedmatter physics, cosmology or finance—is difficult because they are hard to repeat, or they occur very rapidly. Here we report a hightimeresolution study of the evolution of both bosonic and fermionic excitations through an electronic chargeordering symmetry breaking phase transition. Periodically quenching our system with femtosecond optical pulses, we subsequently detect hithertounrecorded coherent aperiodic undulations of the order parameter, critical slowing down of the collective mode and evolution of the particle–hole gap as the system evolves through the transition. Modelling on the basis of Ginzburg–Landau theory is used to reproduce the observations without free parameters. Of particular interest is the observation of spectrotemporal distortions arising from spontaneous annihilation of topological defects, analogous to those discussed by the Kibble–Zurek cosmological model.
COBISS.SI-ID: 23900711
In hopping magnetoresistance of doped insulators, an applied magnetic field shrinks the electron (hole) swave function of a donor or an acceptor and this reduces the overlap between hopping sites resulting in the positive magnetoresistance quadratic in a weak magnetic field, B. We extend the theory of hopping magnetoresistance to states with nonzero orbital momenta. Different from s states, a weak magnetic field expands the electron (hole) wave functions with positive magnetic quantum numbers, m)0, and shrinks the states with negative m in a wide region outside the point defect. This together with a magneticfield dependence of injection/ionization rates results in a negative weakfield magnetoresistance, which is linear in B when the orbital degeneracy is lifted. The theory provides a possible explanation of a large lowfield magnetoresistance in disordered π-conjugated organic materials.
COBISS.SI-ID: 25766439
S časovno ločljivo optično spektroskopijo smo proučevali dinamiko relaksacije neravnovesnih nosilcev naboja v organskih prevodnikih (BEDTTTF)(2)Cu[N(CN)(2)]X (X=Br in Cl). Dinamiki v obeh materialih imata podobno temperaturno odvisnost, ki jo lahko opišemo z relaksacijo nosilcev naboja preko psevdoreže velikosti Δ(PG) ≈ 16 meV za Br sol in 7.0 meV za Cl sol. Zgolj v primeru Br soli pa smo opazili skokovito podaljšanje relaksacijskega časa pri nizkih temperaturah, ki nakazuje dodatno komponento v relaksaciji povezano s superprevodno režo pod kritično temperaturo. Intenzitetna odvisnost dinamike pri nizkih temperaturah nakazuje superpozicijo superprevodne komponente s komponento psevdoreže. Rezultati nakazujejo obstoj fazne separacije med kovinskimi in neprevodnimi deli v Br soli povzročene s fotovzbujenimi neravnovesnimi nosilci naboja.
COBISS.SI-ID: 25507111