arXiv subjects

M. A. Petruska

Publications and source records attributed to M. A. Petruska.

2 recordsLinked to original sources

arXiv2006

Bright-Exciton Fine Structure and Anisotropic Exchange in CdSe Nanocrystal Quantum Dots

We report on polarization-resolved resonant photoluminescence (PL) spectroscopy of bright (spin-1) and dark (spin-2) excitons in colloidal CdSe nanocrystal quantum dots. Using high magnetic fields to 33 T, we resonantly excite (and selectively analyze PL from) spin-up or spin-down excitons. At low temperatures (<4K) and above ~10 T, the spectra develop a narrow, circularly polarized peak due to spin-flipped bright excitons. Its evolution with magnetic field directly reveals a large (1-2 meV), intrinsic fine structure splitting of bright excitons, due to anisotropic exchange. These findings are supported by time-resolved PL studies and polarization-resolved PL from single nanocrystals.

cond-mat.mtrl-sci↗

arXiv2001

The Magnetic Spin Ladder (C_{5}H_{12}N)_{2}CuBr_{4}: High Field Magnetization and Scaling Near Quantum Criticality

The magnetization, $M(H \leq 30$ T, 0.7 K $\leq T \leq 300$ K), from single crystals and powder samples of (C$_{5}$H$_{12}$N)$_{2}$CuBr$_{4}$ has been used to identify this system as an $S=1/2$ Heisenberg two-leg ladder in the strong coupling limit, $J_{\perp} = 13.3$ K and $J_{\parallel} = 3.8$ K, with $H_{c1} = 6.6$ T and $H_{c2} = 14.6$ T. An inflection point in $M(H, T = 0.7$ K) at half-saturation, $M_{s}/2$, is described by an effective \emph{XXZ} chain. The data exhibit universal scaling behavior in the vicinity of $H_{c1}$ and $H_{c2}$, indicating the system is near a quantum critical point.

cond-mat.str-el↗