TY - JOUR
T1 - Experimental apparatus to search for supersolidity in monolayer 4 He on graphite
AU - Kubota, Y.
AU - Toda, R.
AU - Kamada, M.
AU - Nakamura, S.
AU - Matsui, T.
AU - Fukuyama, Hiroshi
N1 - Funding Information:
Acknowledgments We thank Y. Shibayama for useful discussions about designing of the torsional oscillator. We also thank staffs of the machine shop at the Graduate School of Science, The University of Tokyo (UT) for their skillful machining of the experimental apparatus and those of the Cryogenic Research Center, The UT for their stable supply of liquid helium. This work was partially supported by Grant-in-Aid for Scientific Research (A) (Grant No. 22244042) from the JSPS. Y. K. and M. K. acknowledge supports from the ALPS and MERIT programs of the UT, respectively.
PY - 2014/4
Y1 - 2014/4
N2 - We describe some details of a new experimental setup for torsional oscillator (TO) measurement of 4 He monolayers adsorbed on a graphite surface. This setup is designed to seek for the possible supersolid phase, in which crystalline order coexists with superfluidity, in two dimensional (2D) solid 4 He below 300 mK. Among such 2D solids, the commensurate phase in the second layer on graphite is the most hopeful candidate for the novel supersolid phase since it is the lowest-density quantum solid ever found. An exfoliated graphite substrate we used is ZYX which has at least ten times longer surface coherence length compared to Grafoil, an exfoliated graphite most commonly used in previous experiments. The first version of TO we made has the resonant frequency of 786.8 Hz and the Q value of 1.1 × 105 at T ≤ 10 mK. The resonant frequency of this particular TO without any He samples (fcell) showed unexpectedly large temperature variation and non-reproducibility below 1 K as well as sudden jumps when mechanical shocks are applied to the experimental apparatus. We found the stability of f cell is highly correlated with the temperature stability of 1 K pot in dilution refrigerator.
AB - We describe some details of a new experimental setup for torsional oscillator (TO) measurement of 4 He monolayers adsorbed on a graphite surface. This setup is designed to seek for the possible supersolid phase, in which crystalline order coexists with superfluidity, in two dimensional (2D) solid 4 He below 300 mK. Among such 2D solids, the commensurate phase in the second layer on graphite is the most hopeful candidate for the novel supersolid phase since it is the lowest-density quantum solid ever found. An exfoliated graphite substrate we used is ZYX which has at least ten times longer surface coherence length compared to Grafoil, an exfoliated graphite most commonly used in previous experiments. The first version of TO we made has the resonant frequency of 786.8 Hz and the Q value of 1.1 × 105 at T ≤ 10 mK. The resonant frequency of this particular TO without any He samples (fcell) showed unexpectedly large temperature variation and non-reproducibility below 1 K as well as sudden jumps when mechanical shocks are applied to the experimental apparatus. We found the stability of f cell is highly correlated with the temperature stability of 1 K pot in dilution refrigerator.
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U2 - 10.1007/s10909-013-1047-7
DO - 10.1007/s10909-013-1047-7
M3 - Article
AN - SCOPUS:84896387921
SN - 0022-2291
VL - 175
SP - 160
EP - 166
JO - Journal of Low Temperature Physics
JF - Journal of Low Temperature Physics
IS - 1-2
ER -