Reduction of thermal fluctuations in a cryogenic laser interferometric gravitational wave detector

The thermal fluctuation of mirror surfaces is the fundamental limitation for interferometric gravitational wave (GW) detectors. Here, we experimentally demonstrate for the first time a reduction in a mirror's thermal fluctuation in a GW detector with sapphire mirrors from the Cryogenic Laser Interferometer Observatory at 17 and 18 K. The detector sensitivity, which was limited by the mirror's thermal fluctuation at room temperature, was improved in the frequency range of 90 to 240 Hz by cooling the mirrors. The improved sensitivity reached a maximum of 2.2×10(-19) m/√Hz at 165 Hz.     

Discrete dihedral-angle modulation in porphyrin wheels adsorbed on Cu(1 0 0) observed by scanning tunneling microscopy

Conformations of two dodecameric porphyrin wheels adsorbed on a Cu(1 0 0) were probed by using scanning tunneling microscopy (STM). Whereas a wheel consisting of six meso-meso linked diporphyrins was detected as uniform ring structure, several different images with three discrete molecular heights were detected for a wheel consisting of six meso-meso, β-β,β-β triply-linked planar diporphyrins. These results indicate that the former has a conformation similar to that in a free space, while the latter has various conformations with respect to orientation of planar diporphyrin units toward the metal surface. Several discrete STM images of the latter have been interpreted in terms of possible eight conformations, which vary as to relative orientation of neighboring diporphyrin units.     

The Microwave Spectrum of Methyl Formate (HCOOCH3) in the Frequency Range from 7 to 200 GHz

The rotational spectrum of methyl formate (HCOOCH₃) has been observed in the frequency range from 7 to 200 GHz. We newly assigned 1612 lines in the ground torsional state and simultaneously analyzed both A- and E-species data including previously reported lines on the basis of the internal axis method. A total of 3077 lines were fitted to a 1σ standard deviation of 139 kHz, and molecular parameters were determined.     

Brillouin scattering investigation of paraelectric KH2PO4 under applied uniaxial stress

The Brillouin scattering spectra of KH₂PO₄ under an applied uniaxial stress have been studied in the neighborhood of the ferroelectric transition. Dependence of shear acoustic phonon on the uniaxial stress is similar to dependence on electric field. The acoustic phonon is overdamped near T_c, but become underdamped under the applied shear stress. In the case of ΔT(= T — T_c) < ～ 0.05 K, application of stress caused a transition not to have any soft acoustic phonon.     

Texture in the superconducting order parameter of CeCoIn5 revealed by nuclear magnetic resonance

We present a 115In NMR study of the quasi-two-dimensional heavy-fermion superconductor CeCoIn5 believed to host a Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state. In the vicinity of the upper critical field and with a magnetic field applied parallel to the ab plane, the NMR spectrum exhibits a dramatic change below T*(H) which well coincides with the position of reported anomalies in specific heat and ultrasound velocity. We argue that our results provide the first microscopic evidence for the occurrence of a spatially modulated superconducting order parameter expected in a FFLO state. The NMR spectrum also implies an anomalous electronic structure of vortex cores.     

Field-induced thermal metal-to-insulator transition in underdoped La(2-x)Sr(x)CuO(4+delta)

The transport of heat and charge in cuprates was measured in single crystals of La(2-x)Sr(x)CuO(4+delta) (LSCO) across the doping phase diagram at low temperatures. In underdoped LSCO, the thermal conductivity is found to decrease with increasing magnetic field in the T-->0 limit, in striking contrast to the increase observed in all superconductors, including cuprates at higher doping. In heavily underdoped LSCO, where superconductivity can be entirely suppressed with an applied magnetic field, we show that a novel thermal metal-to-insulator transition takes place upon going from the superconducting state to the field-induced normal state.     

Rotational Spectra of XeH and Its Isotopic Species

Frequencies of rotational transitions of XeH⁺ and its isotopic species were measured in the 1–5 THz region with a highprecision far-infrared spectrometer using a tunable radiation source. Measured frequencies were analyzed together with previous microwave and infrared measurements to refine mass-independent Dunham parameters.