λ點

λ點是氦從一般流體氦(I)相變到超流體氦(II)的溫度，在1標準大氣壓下約為2.17 K。氦（I）和氦（II）可以共存的最低壓力是在He氣體−He(I)−He(II)的三相點，是在2.1768 K（−270.9732 °C）及5.048 kPa（0.04982 atm），是該溫度下的飽和蒸氣壓（若在氣封（英語：Hermetic seal）的容器內，純氦氣會在液體表面形成熱平衡）^[1]。氦(I)和氦(II)可以共存的最高壓力是立方晶系氦固體−He(I)−He(II)的三相點，位在1.762 K（−271.388 °C）, 29.725 atm（3,011.9 kPa）^[2]。

λ點的名稱是因為在上述溫度範圍內描繪比熱容和溫度的圖時（在上述的壓力下，例如一大氣壓力），會出現希臘文的字母λ。當溫度接近λ點時，其比熱容會到達其峰值，只有在零重力時才能準確量測到可以說明比熱容發散的臨界指數（為了要讓流體在一體積內的密度是均勻的）。曾在1992年太空船的酬載中量過比λ點低2 nK時的熱容^[3]。

未解決的物理問題：說明He-4在超流體形變時熱容臨界指數

α

理論值和實際值之間的差異原因^[4]

熱容的圖上有出現峰值，而附近的斜率很大，但在該點的值不會趨近無限大，在形變點前後的值都是有限值^[3]。熱容在峰值附近的行為可以用 $C\approx A_{\pm }t^{-\alpha }+B_{\pm }$ 公式表示，其中 $t=|1-T/T_{c}|$ 是對比溫度（reduced temperature）， $T_{c}$ 是Λ點溫度， $A_{\pm },B_{\pm }$ 是常數（在形變點前和形變點後各有一組值）， $α$ 為臨界指數： $\alpha =-0.0127(3)$ ^[3]^[5]。因為在超流體相變時，該指數為負，因此比熱仍為有限值

臨界指數 $α$ 的實際值和最精準的理論判定技術所得值之間，仍有很大的差異^[6]^[4]，這些技術^[7]^[8]^[9]包括高溫膨脹技術、蒙地卡羅方法以及Conformal bootstrapping（英語：Conformal bootstrapping）。

參考資料

^ Donnelly, Russell J.; Barenghi, Carlo F. The Observed Properties of Liquid Helium at the Saturated Vapor Pressure. Journal of Physical and Chemical Reference Data. 1998, 27 (6): 1217–1274. Bibcode:1998JPCRD..27.1217D. doi:10.1063/1.556028.
^ Hoffer, J. K.; Gardner, W. R.; Waterfield, C. G.; Phillips, N. E. Thermodynamic properties of ⁴He. II. The bcc phase and the P-T and VT phase diagrams below 2 K. Journal of Low Temperature Physics. April 1976, 23 (1): 63–102. Bibcode:1976JLTP...23...63H. doi:10.1007/BF00117245.
^ ^3.0 ^3.1 ^3.2 Lipa, J.A.; Swanson, D. R.; Nissen, J. A.; Chui, T. C. P.; Israelsson, U. E. Heat Capacity and Thermal Relaxation of Bulk Helium very near the Lambda Point. Physical Review Letters. 1996, 76 (6): 944–7. Bibcode:1996PhRvL..76..944L. doi:10.1103/PhysRevLett.76.944.
^ ^4.0 ^4.1 Rychkov, Slava. Conformal bootstrap and the λ-point specific heat experimental anomaly. Journal Club for Condensed Matter Physics. 2020-01-31 [2024-01-22]. doi:10.36471/JCCM_January_2020_02 . （原始內容存檔於2020-06-09）（英語）.
^ Lipa, J. A.; Nissen, J. A.; Stricker, D. A.; Swanson, D. R.; Chui, T. C. P. Specific heat of liquid helium in zero gravity very near the lambda point. Physical Review B. 2003-11-14, 68 (17): 174518. Bibcode:2003PhRvB..68q4518L. S2CID 55646571. arXiv:cond-mat/0310163 . doi:10.1103/PhysRevB.68.174518.
^ Vicari, Ettore. Critical phenomena and renormalization-group flow of multi-parameter Phi4 theories. Proceedings of the XXV International Symposium on Lattice Field Theory — PoS(LATTICE 2007) (Regensburg, Germany: Sissa Medialab). 2008-03-21, 42: 023. doi:10.22323/1.042.0023  （英語）.
^ Campostrini, Massimo; Hasenbusch, Martin; Pelissetto, Andrea; Vicari, Ettore. Theoretical estimates of the critical exponents of the superfluid transition in $^{4}\mathrm{He}$ by lattice methods. Physical Review B. 2006-10-06, 74 (14): 144506. S2CID 118924734. arXiv:cond-mat/0605083 . doi:10.1103/PhysRevB.74.144506.
^ Hasenbusch, Martin. Monte Carlo study of an improved clock model in three dimensions. Physical Review B. 2019-12-26, 100 (22): 224517. Bibcode:2019PhRvB.100v4517H. ISSN 2469-9950. S2CID 204509042. arXiv:1910.05916 . doi:10.1103/PhysRevB.100.224517.
^ Chester, Shai M.; Landry, Walter; Liu, Junyu; Poland, David; Simmons-Duffin, David; Su, Ning; Vichi, Alessandro. Carving out OPE space and precise O(2) model critical exponents. Journal of High Energy Physics. 2020, 2020 (6): 142. Bibcode:2020JHEP...06..142C. S2CID 208910721. arXiv:1912.03324 . doi:10.1007/JHEP06(2020)142.

外部連結

What is superfluidity?

[Donnelly-1] Donnelly, Russell J.; Barenghi, Carlo F. The Observed Properties of Liquid Helium at the Saturated Vapor Pressure. Journal of Physical and Chemical Reference Data. 1998, 27 (6): 1217–1274. Bibcode:1998JPCRD..27.1217D. doi:10.1063/1.556028.

[Hoffer-2] Hoffer, J. K.; Gardner, W. R.; Waterfield, C. G.; Phillips, N. E. Thermodynamic properties of ⁴He. II. The bcc phase and the P-T and VT phase diagrams below 2 K. Journal of Low Temperature Physics. April 1976, 23 (1): 63–102. Bibcode:1976JLTP...23...63H. doi:10.1007/BF00117245.

[JPL-3] 3.0 ^3.1 ^3.2 Lipa, J.A.; Swanson, D. R.; Nissen, J. A.; Chui, T. C. P.; Israelsson, U. E. Heat Capacity and Thermal Relaxation of Bulk Helium very near the Lambda Point. Physical Review Letters. 1996, 76 (6): 944–7. Bibcode:1996PhRvL..76..944L. doi:10.1103/PhysRevLett.76.944.

[Rychkov-4] 4.0 ^4.1 Rychkov, Slava. Conformal bootstrap and the λ-point specific heat experimental anomaly. Journal Club for Condensed Matter Physics. 2020-01-31 [2024-01-22]. doi:10.36471/JCCM_January_2020_02 . （原始內容存檔於2020-06-09）（英語）.

[5] Lipa, J. A.; Nissen, J. A.; Stricker, D. A.; Swanson, D. R.; Chui, T. C. P. Specific heat of liquid helium in zero gravity very near the lambda point. Physical Review B. 2003-11-14, 68 (17): 174518. Bibcode:2003PhRvB..68q4518L. S2CID 55646571. arXiv:cond-mat/0310163 . doi:10.1103/PhysRevB.68.174518.

[6] Vicari, Ettore. Critical phenomena and renormalization-group flow of multi-parameter Phi4 theories. Proceedings of the XXV International Symposium on Lattice Field Theory — PoS(LATTICE 2007) (Regensburg, Germany: Sissa Medialab). 2008-03-21, 42: 023. doi:10.22323/1.042.0023  （英語）.

[7] Campostrini, Massimo; Hasenbusch, Martin; Pelissetto, Andrea; Vicari, Ettore. Theoretical estimates of the critical exponents of the superfluid transition in $^{4}\mathrm{He}$ by lattice methods. Physical Review B. 2006-10-06, 74 (14): 144506. S2CID 118924734. arXiv:cond-mat/0605083 . doi:10.1103/PhysRevB.74.144506.

[8] Hasenbusch, Martin. Monte Carlo study of an improved clock model in three dimensions. Physical Review B. 2019-12-26, 100 (22): 224517. Bibcode:2019PhRvB.100v4517H. ISSN 2469-9950. S2CID 204509042. arXiv:1910.05916 . doi:10.1103/PhysRevB.100.224517.

[9] Chester, Shai M.; Landry, Walter; Liu, Junyu; Poland, David; Simmons-Duffin, David; Su, Ning; Vichi, Alessandro. Carving out OPE space and precise O(2) model critical exponents. Journal of High Energy Physics. 2020, 2020 (6): 142. Bibcode:2020JHEP...06..142C. S2CID 208910721. arXiv:1912.03324 . doi:10.1007/JHEP06(2020)142.

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閱論編物質狀態
狀態	固體液體氣體 / 蒸氣等離子體
低能量	玻色–愛因斯坦凝聚費米凝聚簡併態物質量子霍爾效應里德伯物質（英語：Rydberg matter）里德伯極化子（英語：Rydberg polaron）奇異物質超流體超固體光子分子簡併態物質超金屬
高能量	夸克物質（英語：QCD matter） Lattice夸克（英語：Lattice QCD）夸克-膠子漿奇異物質超臨界流體色荷玻璃冷凝物（英語：Color-glass condensate）
其他物態	膠體晶體液晶無定形體玻璃時間晶體準晶體柔粘性結晶（英語：Plastic crystal）磁狀態反鐵磁性亞鐵磁性鐵磁性弦狀網液態超玻璃暗物質反物質
相變	沸騰沸點臨界線（英語：Critical line (thermodynamics)）臨界點結晶凝華蒸發閃蒸凝固 λ點熔化熔點復冰現象飽和流體升華過冷三相點清晰點液晶化點二級相變
數量	熔化熱升華熱汽化熱潛熱潛內能特魯頓規則揮發性
概念	雙結點（英語：Binodal）壓縮流體（英語：Compressed fluid）冷卻曲線‎ 狀態方程萊頓弗羅斯特現象姆潘巴現象有序與無序（英語：Order and disorder (physics)）調幅分解（英語：Spinodal）超導現象過熱蒸汽過熱熱-電介質效應（英語：Thermo-dielectric effect）
列表	相態列表

相關條目

參考資料

外部連結