Possible Thermodynamical Phase Slips in Superfluid 4 He Confined in a 2.5-nm Channel of FSM
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Possible Thermodynamical Phase Slips in Superfluid 4He Confined in a 2.5‑nm Channel of FSM Junko Taniguchi1 · Kento Taniguchi1 · Kousuke Kanno1 · Masaru Suzuki1 Received: 15 July 2019 / Accepted: 17 January 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract We have measured the superfluid response of 4He confined in a 2.5-nm channel and have compared with that of 4He in a 2.8-nm channel. In the 2.5-nm channel, the superfluid growth is gradual regardless of areal density and pressure. In contrast, 4 He in a 2.8-nm channel shows a sharp superfluid onset at low pressure, although it shows a gradual temperature dependence with increasing pressure. The gradual temperature dependence in both channels is well fitted to the function of static superfluid density based on the Tomonaga–Luttinger liquid model. It indicates that the thermal excitation of phase slips plays an important role in the observed superfluid response. Keywords One dimension · Superfluidity · Tomonaga–Luttinger liquid
1 Introduction One-dimensional (1D) quantum many-body systems have attracted many researchers’ interest due to large quantum fluctuations. Since the proposal of the Tomonaga–Luttinger (TL) liquid, a variety of 1D systems such as carbon nanotubes and quantum wires have been studied extensively. Recently, the TL liquid theory has been applied to 1D Bosonic systems. Liquid 4He confined in a nanometer-sized channel without connection is noted as a promising system to study the superfluidity of the 1D Bosonic TL liquid [1]. Regarding how the superfluid coherence is suppressed in 1D systems, two mechanisms are proposed: phase slips which excited “thermally” and “dynamically.” The former one was first proposed by Hirashima et al., who regarded the helicity modulus of a 1D system as the superfluid density, as in the dimension higher than two [2]. They insisted that in the 1D system with a finite length, the superfluid density is suppressed by the thermal excitation of a phase slip between both edges of the * Junko Taniguchi [email protected] 1
University of Electro-Communications, Tokyo, Japan
13
Vol.:(0123456789)
Journal of Low Temperature Physics
channel and that the superfluid onset is determined by the energy gap to excite this phase slip. On the other hand, Maestro et al. calculated the superfluid density based on the TL liquid model for a finite-size system without any assumption on phase slips and confirmed that the temperature dependence of superfluid density coincides with that of Hirashima et al. [3, 4]. The other was proposed by Eggel et al. [5]. They calculated the momentum response to the motion of the channel on the basis of TL liquid model and found that the superfluid onset is determined by the dynamical suppression of quantum phase slips at low temperatures. In their theory, for the 1D system, the helicity modulus which is a thermodynamic (static) property does not equal the superfluid density, and the superfluid response under oscillation can be detected at a higher temperature th
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