Transverse ising spin glass model for quantum spin glass system = 양자 스핀 유리계를 위한 횡적 Ising 스핀 유리 모델

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In this paper we investigate for the infinite-range Ising spin glass model (i.e., Sherrington-Kirkpatrick (SK) model) with a transverse field under static approximation by using the imaginary-time replica formalism. From the investigations we show three important results: First, we show that a replica-symmetric quantum spin glass phase is stable in most of the area of spin glass phase in the temperature-transverse field phase diagram. This confirms the existence of stable replica-symmetric spin glass phase under static approximation, which is contrary to some previous results derived without the static approximation where the replica-symmetric solution is always unstable in the whole spin glass phase. Secondly, we show our theoretical result of nonlinear susceptibility $X_nl$ which conforms to the experimental result of nonlinear susceptibility measurement by Wu et al. [Phys. Rev. Lett. 71, 1919 (1993)] in a quantum spin glass $LiHo_xY_{1-x}F_4$. Thirdly, in classical (SK) spin glass system, we confirm the anomaly in the second temperature derivative of $C_H/T$ near the glass transition temperature $T_g$, associated possibly with the field-dependent variation of entropy in the spin glass transition, which agrees with the previous experimental observation in a classical spin glass system CuMn by Fogle et al. [Phys. Rev. Lett. 50, 1815 (1983)]. We also show that this anomaly is suppressed by the nonzero transverse field of quantum spin glass system, by which we can check for the quantum tunneling competing against spin freezing.
Kim, Jong-Jean김종진
한국과학기술원 : 물리학과,
Issue Date
180940/325007 / 000985043

학위논문(박사) - 한국과학기술원 : 물리학과, 2003.2, [ x, 63 p. ]


quantum spin glass; spin glass; transverse Ising model; 횡적 Ising 모델; 양자 스핀 유리; 스핀 유리

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