## 1 Introduction  
Use of phase-change materials (PCMs) in electrical and optical systems has introduced widespread applications, including uses in optical data storage [1; 2; 3] and photonic nanodevices [4; 5]. Attributes of PCMs include nonvolatile phase changes, rapid switching, and quick responses to stimuli, reasonable data retention, and long-term stability [6; 7; 8]. The exceptional properties of PCMs, including phase-state stability, small crystallization times (\(\sim\)ns), low switching energies (\(\sim\)p), and high endurance potentials (\(\sim\)10\({}^{15}\) cycles), make them perfect materials for ultrafast and low-energy photonic processing [9]. Due to various physical properties of their atomic structures [10], PCMs can work as data storage systems in optical storage discs [11], emerging nonvolatile electronic memories (eNVMs) [6], active optoelectronic nanodisplays [12], and electro-optomechanics [13]. Ge\({}_{2}\)Sb\({}_{2}\)Te\({}_{5}\) (GST) is a chalcogenide PCM that has been used for both nanoelectronic and nanophotonic systems. GST has unique characteristics in terms of both electrical (resistivity) and optical properties, like the refractive index (RI) between its crystalline and amorphous states [14; 15; 16]. The transitions between the two states are attained by localized heating, using optical or electrical energy [14; 17]. Crystalline GST shows higher reflectivity and electrical conductivity than amorphous GST [17]. Recently, a photonic abacus [18] and brain-like computing [19] were realized by exploiting this difference in the properties of crystalline and amorphous GST [16]. The photonic memories using other materials show a volatile behavior [20; 21]; however, a durable and nonvolatile GST-based photonic memory can realize eight-level bit storage in a single device by switching among intermediate states [22]. An external stimulus, such as an electrical pulse or thermal excitation from an elevated temperature above the transition temperature of GST, causes crystallization of as-deposited amorphous PCM. In contrast, another thermal stimulus with a higher magnitude during a shorter time (in the nanosecond range) will return the PCM to its initial state [23]. Absorbers based on metamaterials (MM), which can be used to manipulate light [24], have good flexibility [25] and are easily fabricated on a chip [26]. MM absorbers consist of an artificial arrangement of subwavelength metallic constructions on a dielectric-coated metal film; they also have unconventional properties [27]. Wide-band MM perfect absorbers [28], multiband absorbers [29; 30], and polarization-dependent absorbers have been studied using various materials [31]. MMs with diverse resonances have been used to fabricate broadband absorbers [32; 33]. To realize a reconfigurable MM, the geometry must be controlled and proper materials for dielectric layers and metallic mirrors are required [34]. Metamaterial perfect absorbers (MPAs) have a near perfect absorption \(A\) and an absorption frequency that can be controlled by adjusting the MPA's permittivity \(\varepsilon\), permeability \(\mu\), and dimensions of metallic patterns in artificially periodic structures [35]. The main factors to be considered during the design of MM absorbers are their polarization dependencies, incidence angles, and bandwidths [16]. Perfect absorbers are the most favorable category of the MM absorbers that have been extensively examined in infra-red (IR) regimes [36]. Achieving a broadband absorbance in the visible domain is a useful goal [37], so we investigate an MPA in visible frequencies. Furthermore, the perfect absorption of electromagnetic (EM) waves is the most desirable characteristic of the developed MM absorbers [16]. The imaginary part of dielectric permittivity in the visible range is high in GST, so we expect a high \(A\) in this regime. The high RI leads to a rapid transition between the phases of GST, and an increase in its wideband absorbance [37].